Capacitive electrostatic pickup for stringed musical instruments

Abstract

A capacitive electrostatic pickup assembly for detecting and amplifying the vibrations of a stringed musical instrument. The pickup assembly includes at least one electret material that is configured to provide and maintain an electric field. In exemplary aspects, the pickup assembly includes a pickup plate or foil that is distinct from the at least one electret material and configured to detect the vibrations of the stringed musical instrument.

Description

Attorney Docket No. 38153.0002P1CAPACITIVE ELECTROSTATIC PICKUP FOR STRINGED MUSICAL INSTRUMENTS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 760974, filed February 20, 2025, which is incorporated herein by reference in its entirety.FIELD

[0002] This application relates generally to pickups for stringed musical instruments, and more particularly, to capacitive electrostatic pickups for stringed musical instruments.BACKGROUND

[0003] Amplification of stringed musical instruments has long been a challenge in the performing and recording industry when attempting to capture the true tone (fidelity) of the instrument across its full range of frequencies.

[0004] For stringed instruments, amplification is normally achieved through the use of either a microphone, or an electromagnetic or piezoelectric pickup that first capture the sound waves and vibration of the strings and / or the instrument body in the form of an electrical signal which is then fed into circuitry for signal amplification. Optoelectronic pickups are yet another means used to capture the signals generated by the vibrations of a stringed instrument.

[0005] Microphones are transducers that detect the sound waves produced by the instrument and convert these into electrical signals for amplification. Microphones are often accompanied by problems with unwanted background noise, feedback, low volume, distortion, crosstalk and structural fragility.

[0006] Electromagnetic pickups are another type of transducer made from a magnet (or a number of magnets) wrapped in many thousands of winds of very fine conducting wire. This single coil arrangement is placed under the instrument’s (ferrous) strings whereby the strings, vibrating in the magnetic field, induce a voltage in the coil proportional to the velocity of the string oscillations (not the amplitude). This alternating fluctuation in voltage can range from aAttorney Docket No. 38153.0002P1few millivolts to as high as several volts and can be connected directly, via tone control circuitry, to external amplification equipment.

[0007] Electromagnetic pickups are manufactured in a wide range of configurations with the main differences being the number and configuration of coils and magnets used. Single coil pickups are the most widely used but can suffer from hum caused by electromagnetic interference from other sources. In order to combat this hum, the “humbucker” configuration (FIG. 25) requires two single coil pickups wired in opposing directions as well as having the magnetic poles reversed. This results in the electromagnetic interference (hum) in each coil being out of phase and therefore cancelled (bucked). Subtle differences in the physical makeup of individual electromagnetic pickup such as changes in wire resistance caused by small variations in the number of pickup windings, wire material selection, wire insulation coating, wire winding pattern, magnetic material selection and magnetic strength can have a large impact on the resulting tone, making consistency in expected output signal from the pickup a challenge during manufacture. Many electromagnetic pickup manufacturers require their pickups to be dipped in hot wax for a period of time. Once cooled, the wax helps limit corrosion and further limits unwanted vibrations within the pickup core and the resulting microphonic feedback.

[0008] Also, electromagnetic pickup performance inherently suffers from a peak in frequency response, caused by the pickup’s capacitance and inductance, causing the output to vary significantly across the audible range. Electromagnetic pickups typically peak in frequency in the 2kHz to 5kHz range, just where human hearing is most sensitive.

[0009] All Electromagnetic pickups have fidelity limitations that include, but are not limited to: (1) resonant frequency peaks; (2) susceptibility to electromagnetic interference (EMI); (3) unpredictable influence on tone caused by magnetic eddy currents in metal shielding enclosures used to reduce EMI; (4) limitations in detecting harmonic complexity due to the small percentage of string length used to detect or sense string vibrations; and (5) the wide variability in tone caused by small variations in material selection in the manufacturing process such as magnetic material selection and wire winding parameters.

[0010] Methods for minimizing these undesirable effects include, but are not limited to, time consuming and costly operations in the manufacturing process such as additional coil winding and the widely used practice of hot wax dipping.Attorney Docket No. 38153.0002P1

[0011] An electromagnetic pickup is, in effect, a radio antenna and single coil pickups, in particular, suffer from interference from other ambient electromagnetic signal sources such as fluorescent lighting, computers, televisions, power transformers, domestic appliances and the like. There are a number of remedies to this problem that include coating or lining the internal cavities of the instruments with conductive foil or conductive paint and connecting this coating to the earth terminal. This can create a Faraday shield that can limit the exposure of the coil to electromagnetic interference. Electromagnetic pickups can be partly shielded from electromagnetic interference by use of metal enclosures. However, this can cause “eddy currents” in the metallic parts of the pickup as the changing magnetic field interacts with the metallic components and this in turn can change the frequency response characteristics of the pickup in unpredictable ways. Other remedies include passing the outgoing signal through an external noise cancelling circuit that filters the specific frequencies commonly associated with electromagnetic interference.

[0012] The field created by the electromagnetic pickup can only cover a very small percentage, nominally 5%, of the string length and thus has limited opportunity to sense the full range of harmonics generated during string vibration. Pickups are often placed in groups of 2 or 3 along the length of the instrument strings in an effort to broaden the range of tones and harmonics received by the pickups, either individually, or when the various pickup signals from different locations along the string length are mixed together. Installing groups of pickups in this manner requires extra complexity in terms of compartment cutouts in the instrument, extra mounting requirements as well as the magnets, wiring and circuitry required to allow the combined signals to be mixed into a single output at the output jack.

[0013] Piezoelectric pickups are transducers that offer an alternative to electromagnetic pickups and rely on piezoelectric crystals responding to the physical vibrations of the instrument body caused by the oscillating strings. These vibrations in the body generate a very small signal in the crystals that needs to be pre-amplified before connecting to external amplification equipment. They are more often used in acoustic instruments and are mounted under the bridge where the strings attach to the instrument body. Piezoelectric pickups tend to have a very bright, sharp tonal quality but typically lack “warmth.”

[0014] Piezoelectric pickups response is fundamentally different from an electro-magnetic pickup response. Playing a note with an electromagnetic pickup will produce a certain output voltage while playing the same note with twice the force will produce twice the voltage.Attorney Docket No. 38153.0002P1Playing the same note with a piezoelectric pickup will produce a certain voltage output but playing the note with twice the force will produce an output with approximately four times the voltage. Similarly, when playing with half the force, the output will produce a much (four times) weaker output voltage. This high sensitivity to dynamic range makes playability a problem. In an attempt to address this problem the pre-amplifier usually includes some form of compression to mitigate the high and low peaks of output voltage. This can lead to signal overload, degraded fidelity and a loss in tonal quality.

[0015] Optoelectronic pickups use a combination of light-emitting diodes (LEDs), photodetectors, and optical fibers to detect the vibrations of the instrument strings. LEDs are used to emit light of selected wavelengths onto the instrument strings, which is then either reflected back to the photodetectors or alternatively the strings “shade” the photodetectors. The photodetectors convert the reflected (reflective mode) or shaded light (transmission mode) into an oscillating electrical signal that can then be used for amplification. Optoelectronic pickups offer clear tones and good sensitivity to dynamic range and can be used with most types of string material and suffer less from sound feedback.

[0016] Optoelectronic pickups also use only a very small proportion of the strings length to detect string vibration with the consequent limitations on resulting tone. Transmission mode optoelectronic pickups need to be positioned very close to the instrument bridge thereby only detecting a small subset of string harmonics with consequent limitations on the resulting tone.

[0017] Optoelectronic pickups typically require very careful calibration and can suffer from interference from ambient light, in particular, stage and performance lighting. Various forms of shielding or shading and filtering are often required to limit this interference. Furthermore, optoelectronic pickups are active pickups and thus typically require a preamplifier as well as an external power source. Additionally, optoelectronic pickups are expensive to manufacture and complex to set up.

[0018] Capacitive technology has been used in reed organs where vibrations of the reed are used to change the capacitance between two charge plates thereby generating a signal that can be amplified. Other uses in pianos with vibrating rods or strings, accordions, phonograph pickups and microphones have been developed.

[0019] Electrostatic technology has been patented for use in stringed musical instruments, most recently whereby the electrically grounded, vibrating strings form one ‘plate’ of aAttorney Docket No. 38153.0002P1capacitor and a conductive pickup plate, which is placed under the strings and held at an elevated voltage, forms the other half ofthe capacitor (see, e.g., U.S. Pat. No. 7,514,626, issued April 7, 2009 to Snyder (“Snyder”), which is incorporated herein by reference in its entirety. Snyder requires that the pickup plate serve the dual purposes of sensing the string vibrations and also providing the charge for the electrostatic field. The pickup plate of Snyder is required to be held at 400VDC using complex circuitry, requiring an external battery or mains plug-in power supply. Other similar applications of capacitive pickup technology have been used for pianos and accordions, as well as in microphones and phonographs.

[0020] In general, all categories of pickups used in stringed musical instruments have limitations (problems) with respect to the playing and listening experience (tone, dynamic range) that are inherent in the physics and designs used in their various embodiments. The selection by the musician of one type of pickup over another is a subjective choice based on many complex factors including the genre of music being played and what subtle nuances in tone (fidelity) and playability the player wishes to express. What often drives pickup selection is the requirement to either emulate an existing style or conversely to create a distinctive tone that is identifiable as being uniquely associated with an individual player. This selection is often made in conjunction with special effects ’’pedals” that can be chained together to create these tones.

[0021] Accordingly, a need therefore exists for an improved pickup design suited for applications in stringed instruments that achieves one or more of the following advantages: (1) providing higher fidelity than the prior art via a more uniform frequency response across the audible frequency ranges generated by the stringed instrument; (2) sensing a larger percentage of the strings’ overall length and thereby capturing more harmonic complexity of the vibrating strings; (3) responding more predictably to soft and loud playing (better dynamic range) resulting in an enhanced playing and listening experience; (4) providing improved sustain of the output signal when compared to prior art; (5) permitting construction as a self-contained assembly which is easy to install, either as a replacement for an existing prior art pickup or in a newly manufactured instrument on the factory floor; (6) permitting the use of a power source either integrated into the pickup unit or supplied externally from a power pack; (7) in the case of an integrated power source allowing for easy replacement of the battery or batteries without the need to detune and loosen the instrument strings to gain access to the battery pack; (8) obviates the need for an externally mounted power switch; (9) permitting manufacture fromAttorney Docket No. 38153.0002P1easily sourced materials; and (10) having a signal output that is not highly sensitive to normal variations in material quality and manufacturing processes.SUMMARY

[0022] Disclosed herein is a capacitive electrostatic pickup assembly for detecting and amplifying the vibrations of a stringed musical instrument.

[0023] In various exemplary aspects, the capacitive electrostatic pickup assembly includes at least one electret material. In some aspects, the at least one electret material forms a dielectric layer. In some aspects, the at least one electret material is configured to provide and maintain an electric field.

[0024] In some aspects, the pickup assembly includes a pickup plate or foil that is configured to detect the vibrations of the stringed musical instrument.

[0025] In some aspects, the at least one electret material is fixed plate mounted permanently within the pickup assembly. In another aspect, the at least one electret material defines or is coupled to a retractable or removable blade or plate.

[0026] In some aspects, the at least one electret material is configured to hold a quasipermanent charge. In another aspect, the at least one electret material is configured to hold a charge generated using a triboelectric effect.

[0027] In some aspects, the at least one electret material consists of a single chargeable material. In another aspect, the at least one electret material comprises a composite material. In some aspects, the composite material comprises a high-dielectric substrate material that defines recesses configured to contain triboelectrically chargeable materials.

[0028] In some aspects, the triboelectrically chargeable materials are disposed within the recess of the high-dielectric substrate material, thereby forming the composite material.

[0029] In some aspects, the electric field is exclusively provided by the at least one electret material, and the pickup plate or foil is a separate component from the at least one electret material.

[0030] In some aspects, the pickup assembly further includes an integrated preamplifier.Attorney Docket No. 38153.0002P1

[0031] In some aspects, the pickup assembly further includes an internal DC power supply. In another aspect, the pickup assembly further includes an external DC power supply.

[0032] In some aspects, the retractable or removable blade or plate is configured to provide access to the internal preamplifier and battery supply.

[0033] In some aspects, the pickup assembly includes an electrically grounded metal casing that is configured to provide shielding from external electromagnetic interference.

[0034] In some aspects, the pickup assembly further includes an electrically conductive bridge that is configured to span above strings of the stringed instrument. In some aspects, the electrically conductive bridge is electrically connected to the grounded metal casing, and wherein the electrically conductive bridge is configured to provide further shielding from electromagnetic interference. In some aspects, the electrically conductive bridge is selectively removable from the pickup assembly.

[0035] In another aspect, a stringed musical instrument is disclosed herein. In some aspects, the stringed musical instrument includes a body that defines a compartment and a capacitive electrostatic pickup assembly according to any one of the aspects disclosed herein. In some aspects, the capacitive electrostatic pickup assembly is received within the compartment.

[0036] In another aspect, a method is disclosed that includes: removing a first pickup assembly from a compartment of a body of a stringed musical instrument; and positioning a capacitive electrostatic pickup assembly according to any one of the aspects disclosed herein within the compartment.

[0037] Further systems and methods of using the disclosed capacitive pickup assemblies are also described.

[0038] Additional advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.Attorney Docket No. 38153.0002P1BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosed apparatus and, together with the description, serve to explain the principles of the disclosed apparatus and methods.

[0040] FIG. 1 is a perspective view of an exemplary pickup assembly installed in an instrument with optional EMI shield bridge attached, in accordance with the present disclosure.

[0041] FIG. 2 is a perspective view of an exemplary pickup assembly installed in an instrument with the optional EMI shield bridge removed, in accordance with the present disclosure.

[0042] FIG. 3 is a perspective view of an exemplary pickup assembly removed from an instrument with the optional EMI shield bridge attached, in accordance with the present disclosure.

[0043] FIG. 4 is an exploded view of an exemplary pickup assembly in accordance with the present disclosure.

[0044] FIG. 5 is a perspective view of an exemplary inner case assembly depicting the inner case with the lid sub assembly partly open showing the battery and preamplifier, in accordance with the present disclosure.

[0045] FIG. 6 is a cross-sectional view of an exemplary pickup assembly in accordance with the present disclosure.

[0046] FIG. 7 is an exploded view of another exemplary pickup assembly that has a battery case as a removable sliding component, in accordance with the present disclosure.

[0047] FIG. 8 is a photographic image of an exemplary pickup installed with an optional EMI shield bridge.

[0048] FIG. 9 is a photographic image of an exemplary pickup installed with the EMI bridge removed and with a charge blade retracted for triboelectric charging.

[0049] FIG. 10 is a photographic image of an exemplary pickup installed with blade removed, showing a foil / plate pickup and internal case lid exposed.Attorney Docket No. 38153.0002P1

[0050] FIG. 11 is a photographic image of an exemplary pickup installed, showing easy access for battery change.

[0051] FIG. 12 is a photographic image of an internal lid in an open position showing details of a preamplifier.

[0052] FIG. 13 is a photographic image of an inner case lid positioned to provide battery pack access.

[0053] FIG. 14 is a photographic image showing removal of an exemplary pickup assembly.

[0054] FIG. 15 is a photographic image of an inner case lid in an open position showing preamplifier and battery pack.

[0055] FIG. 16 is a photographic image of an inner case lid in a closed position.

[0056] FIG. 17 is a photographic image of an inner case lid in an open position, with the battery pack open for battery change.

[0057] FIG. 18 is a photographic image of an inner case lid in an open position, with the battery pack partly exposed.

[0058] FIG. 19 is a photographic image of another exemplary pickup assembly having a popup internal case and a side loading sliding battery case for easy battery change.

[0059] FIG. 20 is an exploded view of a preferred embodiment with the preamplifier bottom copper layer as the pickup sensing plate.

[0060] FIGS. 21-22 are schematic diagrams showing equivalent circuits. FIG. 21 is an equivalent circuit for a capacitive pickup. FIG. 22 is an equivalent circuit for an electromagnetic pickup.

[0061] FIG. 23 is a schematic diagram showing a simulated inductance signal chain with a bypass switch.

[0062] FIG. 24 provides a comparison of pickup gain and sustain for an exemplary capacitive pickup as disclosed herein (shown in red) vs a conventional humbucker magnetic pickup (shown in blue).Attorney Docket No. 38153.0002P1

[0063] FIG. 25 is a frequency spectrum graph of a conventional humbucker electromagnetic pickup.

[0064] FIG. 26 is a frequency spectrum graph of an exemplary capacitive pickup as disclosed herein.

[0065] FIG. 27 is an exploded view of a prior art single coil pickup.

[0066] FIG. 28 is an exploded view of a prior art humbucker pickup.DETAILED DESCRIPTION

[0067] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. It is to be understood that this invention is not limited to the particular methodology and protocols described, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

[0068] Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0069] As used herein the singular forms “a,” “an,” and “the” provide disclosure for embodiments in which only a single one of the disclosed items is provided, and unless the context clearly dictates otherwise, can also provide disclosure for embodiments in which a plurality of such items are provided. For example, use of the term “a gripper” can represent disclosure of embodiments in which only a single gripper is provided, as well as disclosure of embodiments in which a plurality of such grippers are provided, and so forth.Attorney Docket No. 38153.0002P1

[0070] All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

[0071] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. Optionally, in some aspects, when values are approximated by use of the antecedent “about,” it is contemplated that values within up to 15%, up to 10%, up to 5%, or up to 1% (above or below) of the particularly stated value can be included within the scope of those aspects. Similarly, in some optional aspects, when values are approximated by use of the terms “approximately,” “substantially,” or “generally,” it is contemplated that values within up to 15%, up to 10%, up to 5%, or up to 1% (above or below) of the particular value can be included within the scope of those aspects. When used with respect to an identified property or circumstance, “substantially” or “generally” can refer to a degree of deviation that is sufficiently small so as to not measurably detract from the identified property or circumstance, and the exact degree of deviation allowable may in some cases depend on the specific context.

[0072] As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0073] Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. In particular, in methods stated as comprising one or more steps or operations, it is specifically contemplated that each step comprises what is listed (unless that step includes a limiting term such as “consisting of’), meaning that each step is not intended to exclude, for example, other additives, components, integers, or steps that are not listed in the step.Attorney Docket No. 38153.0002P1

[0074] As used herein, the term “at least one of’ is intended to be synonymous with “one or more of.” For example, “at least one of A, B and C” explicitly includes only A, only B, only C, and combinations of each.

[0075] The word “or” as used herein means any one member of a particular list and, in alternative embodiments, unless context dictates otherwise, can also include any combination of members of that list.

[0076] It is to be understood that unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; and the number or type of aspects described in the specification.

[0077] The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan would understand that the apparatus, system, and associated methods of using the apparatus can be implemented and used without employing these specific details. Indeed, the apparatus, system, and associated methods can be placed into practice by modifying the illustrated apparatus, system, and associated methods and can be used in conjunction with any other apparatus and techniques conventionally used in the industry.

[0078] In some aspects, this disclosure refers to the terms “electret”, “triboelectrification”, and the “triboelectric series.”

[0079] An electret is a material that is able to maintain, after initial charging, an electric field for a prolonged period (hours / days / months / years). Electrets are the electrostatic analogue of permanent magnets. Permanently charged electret materials are generally complex and costly to manufacture but offer an otherwise effective solution to establishing and maintaining a stable electric field for use in the capacitive pickup. As used herein, electret materials may also be referred to as “chargeable materials.” For instance, electret materials may be provided in the form of a single chargeable material or may be a composite that includes a substrateAttorney Docket No. 38153.0002P1material and an additional chargeable material. In some aspects, both the substrate material and the additional chargeable material are both chargeable materials.

[0080] Triboelectrification is the process by which two initially electrically uncharged bodies become charged with respect to each other when brought into contact, in the case of the disclosed capacitive pickup assemblies by rubbing, and then subsequently separated. Effectively one material is taking up electrons and the other is losing electrons resulting in net opposing charges being created on each material respectively. A well-known example phenomenon occurs when rubbing an inflated balloon on a dry head of hair. The statically-charged hair stands on end as the accumulated charges in each charged hair strand is repelled by other similarly charged hair strands in close proximity.

[0081] A triboelectrically charged material offers an alternate effective solution to a permanently charged electret, provided that the charge can be established or maintained over the required duration of a musical performance. For example, a pickup design solution having a capacitor circuit such as the example depicted in FIG. 21, in which an electret material performs both the function of the dielectric element of the capacitor as well as generating the static electric field for the functioning of the pickup, would be consistent with the inventive steps described herein.

[0082] The triboelectric series, referred to herein, is described in Zou et al., Quantifying the triboelectric series, Nature Communications 10, Article 1427 (2019), which is incorporated herein by reference in its entirety. Accordingly, it is contemplated herein that a triboelectric series is an empirical effort to quantify the tendency to which, and therefore how readily, a material is capable of taking up or losing electrons relative to other materials during the triboelectrification process, which for the purposes of the disclosed capacitive pickup assemblies, comprises briefly rubbing one material with another.

[0083] Overview

[0084] Disclosed herein, in various aspects and with reference to FIGS. 1-21 and 23-26 is a capacitive electrostatic pickup assembly 1 for detecting and amplifying the vibrations of a stringed musical instrument 50. In some aspects, the capacitive electrostatic pickup assembly 1 (also referred to herein as a “capacitive pickup” or “pickup”) can include an electret (e.g., formed as an “electret assembly”) to produce and maintain an electric field. In some aspects, the electret is formed from at least one electret material 10. As further described herein andAttorney Docket No. 38153.0002P1depicted in the figures, the electret material 10 can be integrated into an electret assembly in the form of a retractable / removable electret blade or plate 9 (also referred to herein as a “charge blade,” “electret charge blade,” or “charge plate”) that is either permanently charged or temporarily charged using triboelectric charging.

[0085] In this respect, some aspects of the present disclosure relate to instruments having tribo-electret assemblies. Accordingly, a general description of the operating principles of the provided tribo-electret assemblies follows. As contemplated herein, rubbing two materials selected from opposing halves of the triboelectric series against one another can leave a resulting charge on each thereby creating a temporary electric field within and around the charged material which can be exploited by a capacitive pickup. An expected limitation associated with this approach is that the charge will fade with time as atmospheric moisture and other particles carried in the atmosphere eventually neutralize the charges on the charged material. However, careful selection of triboelectric materials, or combinations of different triboelectric materials, can significantly increase the time for which the charge is maintained. Encapsulating the charged electret in a further dielectric material that limits loss of charge from atmospheric moisture is a further measure for improving charge maintenance. Additionally, several other measures can also be implemented to increase the time for which the charge is maintained, which is important in consideration of the expected duration of a musical performance. Finally, suitable candidates for the triboelectrically charged materials (or combinations of different triboelectric materials) used for the electret (i.e., “electret material”) within the capacitive pickup assembly can hold sufficient charge with a brief rub with an appropriate material.

[0086] Some of the materials most suitable for triboelectric charging are structurally fragile and thus prone to damage when subjected to external mechanical stresses (e.g. foams, thin films, waxes, etc.). In one aspect, the disclosed capacitive pickup assemblies incorporate fragile electret materials into a more durable parent material that can also be a triboelectrically chargeable material to create a composite tribo-electret assembly. The composite tribo-electret assemblies provided herein are more durable, easier to handle, and are still capable of providing an electric field of sufficient strength and longevity for a musical performance.

[0087] Advantageously, the use of an electret to provide the electric field in the disclosed capacitive pickup assemblies obviates the need for a complex electrical charging circuit to maintain the electric field. In various aspects provided herein, the disclosed capacitive pickupAttorney Docket No. 38153.0002P1assemblies further improve on the prior art in that the maintenance of the electric field charge and the detection of the string vibrations are provided by separate and distinct components, and not as a single component, as in the prior art. As previously described, the electric field charge can be maintained by a retractable electret blade that is either permanently charged or temporarily charged using triboelectric charging. A pickup plate / foil is provided as a separate and distinct component from the electret that is used to generate the electric field. In use, the pickup plate / foil is used solely to capture the voltage fluctuations caused by the instrument strings vibrating within the electric field provided by the electret. Accordingly, it is contemplated herein that the electric field can be exclusively provided by the electret material, and that detection of voltage fluctuations can be exclusively provided by the pickup plate / foil.

[0088] The output signal of the disclosed capacitive pickup assembly is created by using electrically grounded instrument strings, constituting, in effect, one half of a capacitor, coupled with a sensing plate (also referred to herein as a “pickup plate”) located under the strings to form the other half of the capacitor, and an electret material or materials, including but not limited to, those that can be triboelectrically charged, positioned laterally between the sensing plate and the strings. In use, the electret material simultaneously provides both the required electric field for the capacitor and acts as the dielectric material separating the two halves of the effective capacitor. When plucked or strummed, the string vibrations cause a detectable signal to be generated on the sensing plate that can, in some aspects, be further amplified by an integrated preamplifier, powered by an internal battery, that are both located below the sensing plate and within the capacitive pickup assembly. Alternatively, where space requirements are limited, the preamplifier and / or battery can be mounted externally to the pickup casing.

[0089] In some aspects, the capacitive pickup assembly does not exert a dampening effect on ferrous string vibrations. The lack of a magnetic field therefore allows the strings to vibrate undamped within the electric field of the capacitive pickup for a longer period of time (greater sustain), thus generating a signal with longer duration.

[0090] Similarly, the disclosed capacitive pickup assemblies are not restricted by a peak in frequency response inherent in electromagnetic pickups and thus are capable of a higher fidelity response, particularly in higher frequency ranges, as well as responding to both subtle and loud, expressive playing, which is often referred to as having excellent dynamic range. Consequently, inherent characteristics of a capacitive pickup can be described as “clear,” “having presence,” “good mid and top range.” Furthermore, the tone of a capacitive pickup isAttorney Docket No. 38153.0002P1less prone to variations in manufacturing techniques or material selection than is the case for electromagnetic pickups, and therefore, the characteristic tonal qualities are much more reproducible.

[0091] Conversely, electromagnetic pickups typically require the instrument strings to be made of ferrous material in order to interact with the magnetic field of the pickup. Advantageously, instruments that include the disclosed capacitive pickup assemblies are not limited to ferrous materials for the instrument strings. Rather, instruments that include the disclosed capacitive pickup assemblies can include strings made from a range of non-ferrous conductive materials such as brass, bronze, or bronze-wound nylon. This allows for a greater range of harmonic nuance and complexity by changing the type of instrument strings.

[0092] Exemplary Pickup Assembly and Instrument

[0093] Disclosed herein, in various aspects and with reference to FIGS. 1-21 and 23-26 is a capacitive electrostatic pickup assembly 1 for detecting and amplifying the vibrations of a stringed musical instrument 50. Referring generally to FIG. 1, an exemplary capacitive pickup assembly 1 is shown integrated into a stringed musical instrument 50. In particular, FIG. 1 depicts the capacitive pickup assembly 1 installed within a compartment 54 defined in the instrument body 51 of the instrument 50. As described above, the capacitive pickup assembly 1 can include a retractable (or removable) electret charge blade 9 that contains an electret material 10. In some exemplary aspects, the electret charge blade 9 can contain a single electret material 10. In further exemplary aspects, the electret charge blade 9 can contain a composite electret material 10 that includes both a triboelectrically chargeable electret material 10 as well as a chargeable material substrate 11.

[0094] In some aspects, the composite material can include the placement of triboelectrically chargeable material 10 into “pockets” (i.e., cavities or recesses) that are defined in another chargeable material substrate 11 that is configured to contain the triboelectrically chargeable material 10. In some aspects, the chargeable material substrate 11 can be a high-dielectric substrate. Accordingly, both materials 10, 11, when charged, can contribute to maintaining the charge. The substrate material 11 can also provide additional structural integrity for the assembly of these electret materials 10 (e.g., in the form of an electret charge blade 9). In further aspects, the at least one electret material may use only a singleAttorney Docket No. 38153.0002P1material for the triboelectrically chargeable material 10 where the electret material 10 has sufficient mechanical integrity.

[0095] In some aspects, the pockets / recesses containing the chargeable material 10 can be configured into any shape. These pockets / recesses containing the chargeable material 10 can be distributed symmetrically across the instrument strings 53 to provide either a uniform charge (and therefore electric field) distribution across the instrument strings 53 or, if required / preferred, the pockets / recesses can be shaped and distributed asymmetrically to provide a greater or lesser charge field intensity for certain strings 53, as needed. With the electret charge blade 9 being removable, this introduces the concept of a “physical” equalizer mechanism that can allow use of chargeable blades 9 with differing charge field distributions. This allows the strength of the output signal to be selectively altered or tuned for individual instrument strings 53. In this aspect, a user can quickly, conveniently, and discreetly use any number of electret charge blade assemblies 9 having differing electret configurations (e.g., containing single materials, composite material, and / or varying geometric configurations) to optimize the sound of the instrument 50 at different points in a single performance. In some optional examples, a different optimized electret charge blade 9 can be used for each and every individual musical score / composition. Accordingly, it is contemplated herein that a first capacitive pickup assembly can be removed from the compartment 54 defined in the body 51 of the instrument 50, and in its place, a second capacitive pickup assembly 1 according to any aspect provided herein can be positioned within the compartment 54 of the instrument 50.

[0096] In some aspects, at least one of the triboelectrically chargeable electret material 10 and the chargeable material substrate 11 can be coupled to the retractable electret charge blade 9 or can cooperate to define the removable electret charge blade 9. However, in yet further aspects, the electret material 10 (and, optionally, the chargeable material substrate 11 in the form of a composite material) can be fixedly coupled to the capacitive pickup assembly 1. In other words, the electret material does not necessarily need to be mounted on a readily removable component. Rather, the electret material 10 (and, optionally, the chargeable material substrate 11 in the form of a composite material) can be provided in the form of a fixed plate mounted permanently within the capacitive pickup assembly 1. A fixed, nonremovable electret can be configured to have a quasi-permanent charge.

[0097] As further depicted in FIG. 1, the capacitive pickup assembly 1 can include an outer case 5 that can be suspended by screws and springs (not shown) from a pickup ring 4, which isAttorney Docket No. 38153.0002P1itself secured to the instrument body 51 above the compartment 54. The instrument strings 53 are strung from the instrument bridge 52 above the capacitive pickup assembly 1 to the instrument neck (not shown), where the strings 53 can be secured to the instrument body 51. In some aspects, the instrument strings extend under a removable EMI shield bridge 6, which can be coupled to the outer case 5. As further depicted in FIG. 1, the electret charge blade 9 can slide in a horizontal plane through a slot 23 in the outer case 5 into matching grooves 20 defined in an inner case 7 positioned within the outer case 5. The triboelectrically charged materials 10, 11 housed in the retractable electret charge blade 9 can thus be easily removed for re-charging by rubbing with an appropriate material. When re-charged, the retractable electret charge blade 9 containing the charged materials 10, 11 can then be re-inserted into the outer case 5 of the capacitive pickup assembly 1.

[0098] As further described herein, the capacitive pickup assembly 1 can further include a pickup sensing plate or foil 13 that is configured to detect the vibrations of the stringed instrument. As further depicted in reference to FIG. 6, when assembled, the pickup sensing plate or foil 13 can be positioned below the electret charge blade 9.

[0099] In use, the electret material 10 of the electret assembly provides an electric field that allows the vibrating instrument strings 53 to generate an alternating voltage that is detected on the underlying pickup sensing plate or foil 13. For instance, in some aspects, when one or more of the electrically grounded metal (ferrous) strings 53 are plucked or strummed, the vibration causes an alternating voltage in the underlying pickup sensing plate or foil 13, which can be mounted (optionally, fixedly mounted) on the outer face of the lid / door 8 of the inner case 7 below the retractable electret charge blade 9. (See, e.g., FIG. 4).

[0100] Optionally, this alternating voltage provides a signal that can be amplified by an integrated preamplifier 14. Thus, in an optional aspect, as depicted in FIG. 4, the capacitive pickup assembly 1 can include a preamplifier 14 housed in the inner case 7 and optionally powered by low voltage batteries enclosed in the battery case 15, also optionally contained in the inner case 7. These components can be conducted via an insulated wire through a cable access hole 18 (not shown) in the inner 7 and outer 5 cases to an external amplifier or initially through the instrument's tone control circuit and then on via a signal cable to an external amplifier or other equipment. Furthermore, a preamplifier power switch casing 19 can be attached to the side of the outer case 5. The preamplifier power switch casing 19 can house the power switch 12.Attorney Docket No. 38153.0002P1

[0101] As depicted in FIG. 2, the removable EMI shield bridge 6 can be attached to the pickup outer case 5 by small button magnets 16 (obscured) and sits over the instrument strings 53. This EMI shield bridge 6 can be easily detached according to the preference of the artist by simply exerting a suitable force to overcome the magnetic attraction between magnets 16 in the outer case 5 and corresponding magnets 16 in the EMI shield bridge 6. In some aspects, the magnets 16 can be secured using a conductive glue to maintain conductivity between the magnets 16 and the outer case (e.g., a metal casing) and the EMI shield bridge 6. If the instrument body 51 and EMI shield bridge 6 have a non-conductive protective coating, it may be necessary to remove the coating where the button magnets 16 are mounted to allow for electrical conductivity to be enabled between the casing and the EMI bridge 6. The pickup ring 4 can define an appropriate cut-out to allow for the vertical movement of the pre-amplifier power switch 12 as the capacitive pickup assembly 1 moves up or down when the pickup distance from the strings 53 is being adjusted by small screws.

[0102] In one aspect, the exemplary aspect of the pickup assembly depicted in FIG. 1 , the outer dimensions (width across the instrument strings 53 and length along the axis of the instrument strings 53 as well as the depth of the capacitive pickup assembly 1 in the instrument compartment 54) of the capacitive pickup assembly 1 are constrained by the existing dimensions of a prior art pickup that the capacitive pickup assembly 1 might replace. Without these constraints, a capacitive pickup assembly 1 can be manufactured that can detect string vibrations over a longer proportion of the string length and a wider dimension across the strings with the subsequent quality enhancements (including but not limited to higher gain, more harmonic complexity) to the pickup output. This design benefit can be maximized in stringed instruments built specifically to accommodate the optimally sized capacitive pickup assemblies 1 described herein.

[0103] As previously described, the capacitive pickup assembly can include an optional conductive bridge 6 (e.g., “EMI metal bridge” or “EMI bridge”), which can provide shielding from ambient electromagnetic interference. As previously described with reference to FIG. 2, the EMI metal bridge 6 can be attached to the main outer case 5 using a number of small button magnets 16 inserted in the outer case 5 and corresponding legs of EMI bridge 6. FIG. 2 depicts the capacitive pickup assembly 1 installed on an instrument 50 as in FIG. 1, but with the EMI shield bridge 6 removed, revealing the button magnets 16. Other mechanisms for attaching the EMI bridge 6 to the capacitive pickup assembly 1 can include but are not limited to, forAttorney Docket No. 38153.0002P1example, mechanical clips or clasps, are appropriate as long as electrical continuity is maintained between the capacitive pickup assembly 1 and the EMI bridge 6. In some further aspects, the capacitive pickup assembly 1 can include a grounded metal casing as the outer case 5. The grounded metal casing 5 can be configured to provide additional shielding from external electromagnetic interference. Further still, in some aspects, the electrically conductive bridge 6 can be configured to span above the strings 53 of the stringed instrument 50 and connect electrically to the grounded metal casing 5. Accordingly, the electrically conductive bridge 6 can be configured to provide further shielding from electromagnetic interference. In some additional aspects, the electrically conductive bridge 6 can be selectively removable from the capacitive pickup assembly 1.

[0104] As described throughout this disclosure, the capacitive pickup assembly 1 can include the use of the chargeable electret material 10 for the maintenance of an electric field, acting, in addition, as the dielectric material 11 for the effective capacitor formed between the grounded instrument strings 53 and the pickup sensing plate or foil 13 positioned below the retractable electret charge blade 9. As further disclosed herein, it is contemplated that the electret material 10 of the disclosed capacitive pickup assemblies can comprise a permanent electret material or a tribo-electret material. In use, it is contemplated that the electret material 10 of the disclosed capacitive pickup assembly 1 can maintain an electric field without the need for a dedicated power source or dedicated circuitry. This advantage is in contrast to previous electrostatic designs, such as Snyder, which does not use an electret material and which requires a dedicated high voltage power source and associated circuitry for charging a pickup plate.

[0105] Furthermore, the disclosed capacitive pickup assembly 1 provides additional advantages in comparison to Snyder. For example, whereas Snyder embeds a pickup plate within dielectric material to avoid undesirable electrical conduction, the disclosed capacitive pickup assembly 1 uses an electret material 10 that serves the dual purpose of maintaining an electric field and acting as a dielectric material. Accordingly, as long as the electret material 10 of the disclosed capacitive pickup assembly 10 is operable to maintain an electric field, the electret material 10 will also serve the purpose of a dielectric material. In contrast, when the dielectric material of Snyder is exhausted or degraded, an unsafe electrical condition (such as, for example, a short circuit between the charged plate and grounded components) can result. As an additional example, Snyder requires a coupling capacitor to separate DC signals fromAttorney Docket No. 38153.0002P1AC signals and to block DC signals from passing to an amplifier connected to the instrument. If the coupling capacitor of Snyder malfunctions, there is a possibility of 400V DC signals reaching the amplifier, which can result in an unpleasant experience for the user (and others in the area) and potential damage to the amplifier. In contrast, the disclosed capacitive pickup assembly 1, which substantially avoids the introduction of high voltage DC bias, does not require a coupling capacitor to provide a functional pickup assembly and presents no shock hazard to the user.

[0106] A further advantage of the capacitive pickup assembly 1 is apparent when comparing the equivalent electrical circuits of a capacitive pickup with a conventional electromagnetic pickup. Turning now to FIGS. 21 and 22, FIG. 21 depicts an exemplary equivalent electrical circuit of the capacitive pickup assembly 1 , whereas FIG. 22 depicts an exemplary equivalent circuit of conventional electromagnetic pickups found in the prior art.

[0107] In particular, FIG. 21 shows schematically how the positioning of the electret materials 10, 11 between the strings 53 and the pickup sensing plate or foil 13 enable the electret to perform both the function of the dielectric element of the capacitor as well as generating the static electric field for the functioning of the capacitive pickup assembly 1. Notably, the capacitive pickup circuit of FIG. 21 inherently lacks the inductive and resistance elements inherently contained in the electromagnetic pickup circuit of FIG. 22. These elements in the prior art limit the fidelity of the pickup response by causing inductive peaks in the frequency response. Accordingly, this difference enables capacitive pickup designs to be significantly less prone to the limiting effects to output caused by inductive frequency peaks, undesirable variations in pickup winding resistance, in turn caused by variations in electromagnetic winding parameters (including but not limited to variations in wire gauge, wire coating and winding count) as well as variabilities in magnetic field strength cause by variations in magnetic material selection and the process of magnetizing the electromagnetic pickup magnet cores. This is one of several reasons why the output signal of a capacitive pickup is capable of representing a less distorted signal output and improved fidelity relative to the artist’s playing than can be achieved with electromagnetic pickup designs.

[0108] Additionally, conventional capacitive / electrostatic pickups provided the prior art typically require complex external electric circuitry to generate an electric field in the pickup, whereas the capacitive pickup assembly 1 described herein utilizes low-cost triboelectrically charged electret materials. Moreover, these electret materials can be configured to serve asAttorney Docket No. 38153.0002P1both the dielectric material required by the capacitor in the equivalent circuit as well as maintain the electric field required for the operation of the pickup without the need of a power supply.

[0109] In view of the foregoing description, and as further explained below, it is contemplated that the disclosed capacitive pickup assembly 1 can include one or more of the following advantageous techniques: (1) using a triboelectrically charged material to create an electric field (optionally, using a polymer, although other materials, such as a wax, can be used); (2) providing an electret that is retractable for charging, providing access to internals of the pickup assembly, and / or switching a preamplifier on or off; (3) providing separate and distinct pickup plate (e.g. foil) and charged electret structures (rather than using a combined pickup / high voltage charge plate); (4) using an electret to both (a) create / hold a charge and (b) act as a strong dielectric that helps increase the effective capacitance; and (5) using the bottom copper layer of the preamplifier PCB as the pickup plate (e.g. foil) that thereby reduces EMI interference by allowing for a very short connection between the pickup plate and the preamplifier input, thereby limiting the potential side effects of EMI interference. In some aspects using the bottom copper layer of the preamplifier PCB in this way, as depicted in FIG.16, can reduce the component count and provide ease of assembly as well as allow for easy variation in pickup plate geometry that can be used to selectively modify by design the output signal across the instrument strings. For example, the signal strength associated with each string can be proportional to the area of conductive material in the pickup plate under each string. By selectively increasing or decreasing this area of conductive material in the pickup plate under each string, the signal strength can be modified accordingly providing a form of EQ built into the pickup plate that can, for example, provide more bass or treble response as required.

[0110] In some aspects, materials for the triboelectrically charged electret include, but are not limited to, closed cell polymer foam, in particular, polyethylene. Polyethylene has a strong negative triboelectric tendency thereby enabling charge to be generated easily. In addition, polyethylene has very high resistivity and will therefore hold electrons for long periods as there are few conduction discharge paths. The closed cell structure of the foam traps charges internally in the multitude of tiny sealed / closed air pockets that isolate each pocket from its neighbor, isolate charged surfaces from the environment and reduce internal conduction even further. The very large micro-textured surface of closed cell foam provides a very large surface area for charging and allows the charge to be distributed across many isolated micro-surfacesAttorney Docket No. 38153.0002P1(thousands of very small charging sites instead of one smooth surface). Furthermore, due to the mechanical springy nature of the foam, the simple act of handling can cause internal friction between cell walls which leads to further charging.

[0111] In yet further additional aspects, the charged electret can be encased in an enclosing sheath of dielectric material that effectively shields a triboelectrically charged electret from atmospheric moisture and particles thereby reducing the rate of discharge of the electret and consequently increasing the duration of the electric charge.

[0112] FIG. 3 depicts an exemplary capacitive pickup assembly 1 removed from the instrument 50. Unlike FIG. 1, FIG. 3 depicts the outer case feet 17 as visible. The outer case feet 17, which are located within the instrument compartment 54 when installed, have threaded holes to match similar holes in the pickup ring 4. Screws are passed through the holes in the pickup ring 4, then through springs and then finally through the threaded holes in the outer case feet 17 to thereby allow the outer case 5 to be suspended from the pickup ring 4 under the spring tension. Adjusting these screws allows the height of the outer case 5 and hence the inner case 7 and retractable electret charge blade 9 to be adjusted relative to the instrument strings 53. The closer the strings 53 are to the charge material 10, 11, the stronger the resulting signal that is generated at the pickup sensing plate or foil 13. Some instruments may not require this pickup ring 4, as the pickup assembly 1 can be attached directly to the instrument body 51 via holes in the outer body feet 17.

[0113] In another aspect of the disclosed capacitive pickup assembly 1 , the volume of space in the pickup conventionally occupied by magnets and wire coils is no longer utilized, because these components can be discarded. As depicted in FIGS. 4-6 and 12-15, this void can, optionally, be repurposed to contain the preamplifier 14 and, optionally, the associated battery power source 15. Although not required, it is contemplated that incorporating all the components including the preamplifier 14 and battery or batteries within the pickup outer case 5 can provide an easily implementable “drop in” replacement for some existing humbucker pickups without requiring modifications to the instrument body or the mounting of an external battery pack. While the dimensions of a humbucker pickup provide sufficient space for the capacitive pickup assembly 1 discussed herein, further exemplary aspects of the disclosed capacitive pickup assembly 1 can be implemented to replace smaller format single coil pickups using the same principles. Accordingly, it is contemplated herein that a first pickup assembly, such as may be found in the prior art, can be removed from the compartment 54 defined in theAttorney Docket No. 38153.0002P1body 51 of the instrument 50, and in its place, a second capacitive pickup assembly 1 according to any aspect provided herein can be positioned within the compartment 54 of the instrument 50.

[0114] FIG. 4 depicts an exploded view of the capacitive pickup assembly 1 revealing all components of an exemplary assembly. The capacitive pickup assembly 1 can be assembled and then installed into the instrument 50 in the following order: (1) the optional preamplifier 14 can be fixed into the inner case 7; (2) the battery pack subassembly 15 can be inserted into the inner case lid 8; (3) the pickup sensing plate or foil 13 can be attached to the top of the inner case lid 8 and connected to the optional preamplifier 14 input (when provided); (4) the connecting wires (not shown) can then be attached to the optional preamplifier 14 (when provided) and threaded through cable aperture 18; (5) the inner case lid 8 can then be snapped into the inner case hinges 21; (6) the signal and power cables (not shown) can then be passed through the outer case 5 exit hole 18 while the inner case 7 is inserted into the outer case 5; (7) the power switch case 19 and the power switch 12 can then be secured to the outer case 5; (8) the power leads can then be subsequently secured to the power switch 12; (9) the pickup ring 4 can then be secured to the outer case feet 17 of the outer case 5 using threaded screws and springs, for example; (10) the capacitive pickup assembly 1 can then be inserted into the instrument compartment 54 and secured by the pickup ring screw holes 22 to the instrument body 51 (not shown); (11) once the capacitive pickup assembly 1 is installed, the electret charge blade 9 can be charged triboelectrically and inserted into the capacitive pickup assembly 1 through the slot 23 in the wall of the outer case 5 and into the grooves 20 of the inner case 7; and (12) the EMI shield bridge 6 can then be attached and removed as required to reduce ambient electromagnetic interference to a minimum. However, in further aspects, the capacitive pickup assembly 1 can be assembled according to comparable steps performed in any other order sufficient to assemble the capacitive pickup assembly 1 and stringed musical instrument 50.

[0115] In another aspect, the optionally integrated preamplifier 14 and batteries (when provided) can be accessed through the hinged lid / door 8 of the inner case 7, thereby enabling the preamplifier batteries to be conveniently changed when they become depleted without the need to remove the entire capacitive pickup assembly 1 from the instrument 50.

[0116] In yet another aspect, in some exemplary aspects of the disclosed capacitive pickup, the electret assembly (e.g., electret materials 10, 11 of the chargeable electret blade 9) isAttorney Docket No. 38153.0002P1rechargeable within the capacitive pickup assembly 1, thus creating the opportunity to enable triboelectric charging by rapid repeated insertions / retractions during a performance (between songs). This can be achieved by providing a suitable material such, that when assembled, and the chargeable electret blade 9 is retracted and re-inserted, the said material rubs against the electret assembly and triboelectrically charges the electret material of the electret assembly to create the required electric field without the need to be charged by hand.

[0117] FIG. 5 depicts an exemplary aspect with the inner case 7 and the inner case lid 8 containing the battery pack subassembly 15, partly opened. In this example, the pickup sensing plate or foil 13 is fixed into a recess on the outer surface of the inner case lid 8 and is electrically connected through a hole in the top of the lid to the signal input of the preamplifier 14 (when provided). The inner case lid 8 is shown in the partly open position as might be the case when changing batteries. As further depicted in reference to FIG. 13 and FIG. 17, the battery pack assembly 15 can be swiveled within the inner case lid 8 to provide access for changing batteries.

[0118] FIG. 6 depicts a cross-section of the exemplary aspect shown in FIG. 5 and the relationship of the internal components. The outer case 4 houses the inner case 7, which has a hinged lid 8 that can fold up when the removable EMI shield bridge 6 is removed and the retractable electret charge blade 9 is removed through the slot 23 defined in the outer case 5 wall. Optionally, the inner case lid 8 has two retaining slots to hold the preamplifier 14 and battery pack subassembly 15. In these configurations, the inner case lid 8 can have the pickup sensing plate or foil 13 fixed to the outer surface and connected electrically to the preamplifier 14 input via a hole in the top of the lid 8.

[0119] FIG. 20 depicts an exemplary aspect in which the battery supply 15 to the capacitive pickup assembly 1 can be located externally to the capacitive pickup assembly 1. This example obviates the need for internal batteries within the capacitive pickup assembly land greatly simplifies the design. The outer metal case 5 can be secured to the instrument body 51 via the two outer case feet 17. The inner case 7 can hold the preamplifier PCB 14 with the bottom copper layer of the preamplifier PCB 14 facing upwards, thereby allowing this layer to act as one half of the capacitive system. The other plate of the capacitive system is (as before) created by the vibrating instrument strings 53. The electret charge blade 9 can include a triboelectrically chargeable material 11 or quasi-permanently charged material that holds or encases the chargeable material 10. As depicted, the electret charge blade 9 is configured to slide in and out of the body of the capacitive pickup assembly 1 through the slot 23 in the body.Attorney Docket No. 38153.0002P1The electret charge blade 9 can then slide on the grooves 20 defined by the inner case 7. The optional EMI bridge 6 can be attached temporarily to the outer case 5. In this exemplary aspect, the mechanism for securing the EMI bridge 6 is a set of button magnets 16 in the outer 5 or inner 7 case of the capacitive pickup assembly 1. Battery power to the preamplifier 14 is provided by a power lead as part of the cable assembly carrying the signal and ground wires that exit the capacitive pickup assembly 1 case 5 through a suitable hole (not visible) in the case 5.

[0120] In the exemplary capacitive pickup assembly 1 depicted in FIG. 20, the bottom copper layer of the preamplifier PCB circuit board 14 can be used as the pickup sensing plate or foil 13 and a short “via” connection through the preamplifier PCB circuit board 14 to the preamplifier input on the PCB top layer. This can provide an extremely short track from the sensing plate to the input of the preamplifier circuit, thereby reducing the potential for EMI interference as well as simplifying the design by combining the pickup sensing plate or foil 13 and the preamplifier PCB 14 into a single component. In addition, varying the amount and distribution of copper under a particular string 53 can modify the output signal for the frequencies associated with that string. Therefore, using the PCB bottom copper layer as the pickup sensing plate or foil 13 allows for various geometric designs to be utilized to influence the output signal of each of the instrument strings 53 and the capacitive pickup assembly 1 as a whole according to the preference of the user.

[0121] In some aspects, FIG. 7 depicts a further example of the capacitive pickup assembly 1 with an exploded view of the main components with the battery case 15 as a horizontally sliding component that slides through the external case slot 23 to enable a battery change without the need to loosen and detune the instrument strings 53 to gain access to the battery holder 28.

[0122] Referring generally to FIGS. 8-19, an exemplary capacitive pickup assembly 1 is provided. FIG. 8 depicts the exemplary capacitive pickup assembly 1 positioned within the compartment 54 defined in the body 51 of the stringed musical instrument 50. In particular, FIG. 8 shows the electret charge blade 9 installed through the slot 23 of the outer metal case 5. FIG. 9 depicts the exemplary capacitive pickup assembly 1 with the EMI shield bridge 6 removed and the electret charge blade 9 retracted. Accordingly, the pickup sensing plate or foil 13 is exposed. As shown, the electret charge blade 9 includes a chargeable material 10 embedded within recesses of a dielectric substrate material 11. FIG. 10 depicts the exemplaryAttorney Docket No. 38153.0002P1capacitive pickup assembly 1 with the electret charge blade 9 fully removed. As further depicted in FIG. 11, the instrument strings 53 can be parted to fully reveal the pickup sensing plate or foil 13, which is mounted on the opposite side of the hinged lid 8. As depicted in FIG.12, the hinged lid 8 can be pivoted to reveal a battery subassembly 15 contained within the hinged lid 8. In some aspects, the battery subassembly 15 can be pivoted within the hinged lid 8 to provide ease of access for changing the battery as necessary. Furthermore, as depicted in FIGS. 12-13, an optional preamplifier 14 can be positioned within the void.

[0123] FIGS. 14-19 depict the exemplary capacitive pickup assembly 1 removed from the compartment 54 of the musical instrument 50. FIG. 15 further depicts the components of the exemplary capacitive pickup assembly 1 positioned within the inner 7 and outer 5 cases. Moreover, the outer case 5 is positioned within the pickup ring 4. FIG. 16 depicts the inner case 7 removed from the outer case 5. FIG. 17 shows the battery subassembly 15 swiveled relative to the hinged lid 8 and opened to expose a battery positioned therein. FIG. 18 depicts the power switch casing 19, and the power switch 12 housed therein, attached to the side of the outer case 5. FIG. 19 depicts the capacitive pickup assembly 1 disassembled so as to permit changing of the batteries.

[0124] Additional Optional Aspects

[0125] Preamplifier

[0126] Optionally, as depicted in FIG. 4, the capacitive pickup assembly 1 can include a preamplifier 14 that can be used to boost the pickup signal detected at the sensing plate 13 before being routed through any internal tone control circuitry and then on to external amplifiers or other equipment.

[0127] Easy Preamplifier Battery Change

[0128] Optionally, as depicted in FIG. 7, the capacitive pickup assembly 1 can include two sliding components for changing the battery. The pop-up inner case 24 can slide vertically between two positions on spring loaded pogo pins 26 which are mounted on the preamplifier PCB 14. These pogo pins 26 connect the battery positive and negative terminals to the PCB positive and negative rails. The third spring loaded pogo pin connects the pickup plate 13 mounted on the top surface of the pop-up inner case 24 to the PCB preamplifier input. TheAttorney Docket No. 38153.0002P1pickup sensing plate or foil 13 can be connected to a conducting plate on the underside of the pop-up inner case 24, and thereby to the pogo pin, by a simple electrical connection.

[0129] The pop-up inner case 24 can contain horizontal sliding rails 25 that can accommodate the sliding battery holder 28 and battery holder lid 27. When the pop-inner case 24 is in the battery change position, the battery case can slide out through the slot 23 in the outer case 5. The battery holder lid 27 can then be removed from the sliding battery holder 28 to permit changing of the battery. The battery holder lid 27 provides a series electrical connections between the two cell batteries using a simple integrated leaf sprung connector. The lid 27 can then be replaced and the sliding battery holder 28 inserted back into the pop-up inner case through the slot 23 in the outer case 5. The pop-up inner case 24 can then be pressed down under spring tension into the operating position where it can be held in place by the inner case securing latch 29, which engages with the outer case securing latch notch 33. In the operating (down) position, the PCB pogo pins 26 provide electrical connectivity between the batteries and the preamplifier PCB 14 and the pickup sensing plate or foil 13.

[0130] Reed Switches for Preamplifier Power Switch and Battery Status Indicator

[0131] Another aspect of the disclosed capacitive pickup assemblies 1 allows for a small reed switch magnet 32 positioned under the side of the electret charge blade 9 furthest from the handle, to not only switch on the power to the preamplifier 14 via a reed switch but also to temporarily switch on the battery status indicator with a second reed switch as it is initially inserted into the outer case 5. To provide power to the preamplifier PCB 14 a reed switch 30, can be mounted on the inner wall of the main inner case 7 such that when the retractable electret charge blade 9 is fully inserted into the inner case 7 through the slot 23 of the outer case 5, a small reed switch magnet 32, mounted in a recess in the base of the retractable electret charge blade 9 causes the reed switch 30 to operate and provide power to the preamplifier 14. To turn off power to the preamplifier 14, the retractable electret charge blade 9 only needs to be retracted a fraction to disengage the preamplifier power reed switch 30 and thereby power down the preamplifier 14.

[0132] A further aspect of the disclosed capacitive pickup assemblies 1 allows for the reed switch magnet 32 to be used to operate a second battery status reed switch 31 mounted on the opposite wall to the preamplifier reed switch 30 such that as the retractable electret charge blade 9 is inserted into the grooves 20 on the inner case 7, the reed switch magnet 32 willAttorney Docket No. 38153.0002P1operate temporarily, allowing a simple battery status circuit with an LED mounted on the preamplifier 14 to provide an indication of the remaining charge available in the batteries. Once the retractable electret charge blade 9 is fully inserted in the operating position, the reed switch magnet 32 will be too distant to power the status indicator circuit and the indicator will turn off. The two reed switches 30, 31 can be positioned sufficiently distant from one another such that the magnet 32 is never able to operate both the power reed switch 30 and the battery status read switch 31 concurrently. This provides a mechanism to check battery status without the need for an externally mounted manual switch and without the need for a permanently powered LED indicator that could drain the battery more rapidly than is desirable.

[0133] Electret Assemblies

[0134] As previously described herein, the electret charge blade design can utilize multiple materials, selected and configured such that, when triboelectrically charged, the composite electret charge blade is able to establish and maintain an electric field sufficient for a more extensive musical performance than a blade configured with a single electret. In further optional aspects, some electret assemblies can include one or more of the following features:

[0135] (1) Single layer of triboelectrically chargeable material used for the electret housed in the retractable electret charge blade. In this optional aspect, an example capacitive pickup assembly can include the use of a single triboelectrically chargeable material as the electret providing the electric field source.

[0136] (2) Single permanently or quasi-permanently charged electret housed in the retractable electret charge blade. In this optional aspect, an example capacitive pickup assembly can include the use of a permanently or quasi-permanently charged electret material as the electric field source. In some aspects, the at least one electret material is configured to hold a charge generated using a triboelectric effect.

[0137] (3) Multiple layers of triboelectrically chargeable material used for the electret housed in multiple layers of retractable electret charge blades. In this optional aspect, an example capacitive pickup assembly can include the use of multiple layers of independently charged electret layers whose combined electric fields result in a stronger overall electric field and thereby a larger output signal from the capacitive pickup assembly.Attorney Docket No. 38153.0002P1

[0138] (4) Composite triboelectrically chargeable material electret housed in the retractable electret charge blade. In some optional aspects, as previously described herein, the disclosed capacitive pickup assemblies can include an electret charge blade design that uses multiple materials, selected and configured such that, when triboelectrically charged, the composite electret charge blade is able to establish and maintain an electric field sufficient for a more extensive musical performance than a simpler blade configuration. This example involves the use of a triboelectrically chargeable electret made from a combination of two or more materials. One material, for example, can be a high-dielectric substrate material that is configured to provide structural integrity while the other triboelectrically chargeable material (or materials) will provide characteristics that prolong the duration of the electric field. In some aspects, the triboelectrically chargeable can be disposed within recesses (i.e., pockets or voids) defined in the high-dielectric substrate material. One practical material combination can include teflon (PTFE) as the substrate and carnauba wax as the material used within the pockets / voids that can extend the duration of a triboelectric charge . This provides a chargeable material electret assembly that, once charged, will hold an electric field for sufficient duration for a musical performance as well as maintaining mechanical integrity. In such examples, recesses within the chargeable substrate can be manufactured with any shape and distributed symmetrically or asymmetrically across the instrument strings to provide signal output modification and “equalizing” as required.

[0139] Slot Seal Around the Electret for Easy Charging

[0140] In an optional aspect, an example capacitive pickup assembly can include the use of a seal in the slot on the outer wall of the pickup that can make contact with the top and / or bottom surfaces of the triboelectrically chargeable electret. The seal can be manufactured from a material such that when rubbed against the electret material, a charge is created on the electret. The electret can then be easily charged by simply pulling and pushing the retractable blade to create the required electric field without the need to remove the blade entirely for the purpose of triboelectric charging.

[0141] Pickup Plate Integrated into Retractable Charge Blade

[0142] In one optional aspect, an example capacitive pickup assembly can include the placement of the pickup plate in a channel on the underside of the removeable charge blade.Attorney Docket No. 38153.0002P1In some aspects, this can require the use of electrical spring contacts to provide connectivity between the pickup plate on the charge blade and the input terminal of the preamplifier.

[0143] Larger Pickup Dimensions as an Original Equipment Manufactured Product

[0144] Without the dimensional constraints on the pickup that are present when placing existing prior art pickups into existing instruments, it is possible to manufacture a capacitive pickup assembly as described herein that will detect string vibrations over a longer proportion of the string length as well as a wider dimension across the strings with the subsequent enhancements including but not limited to higher gain and potentially capturing increased harmonic complexity on the pickup output. Such arrangements are possible were an instrument manufacturer to design and manufacture an instrument from scratch using the capacitive pickup disclosed herein.

[0145] Multiple Layered Capacitor Pickup Plate

[0146] In one optional aspect, the disclosed capacitive pickup assembly uses multiple layers of alternating capacitor plates and insulating dielectric material between the charged material and the pickup plate.

[0147] External Power Supply

[0148] In some optional aspects, the disclosed capacitive pickup assembly can include an external power supply. Some users may prefer to have the battery supply mounted externally, on or in the instrument, allowing for a larger capacity battery and rapid battery change. This can be achieved by replacing the battery connection on the preamplifier from the internal case with a connection to the external battery case. This also allows for larger batteries to be used with a corresponding increase in battery life. In some aspects, the external power supply can utilize a 9V battery housed in an external battery case in the form of a separate compartment on the instrument. In addition, as depicted in FIG. 20, this allows for a smaller overall pickup outer case to be used such that the capacitive pickup assembly can be rendered compatible as a replacement for a wider range of electromagnetic pickups.

[0149] Single Coil Electromagnetic Pickup Replacement

[0150] In another aspect, the capacitive pickup assembly may require manufacturing within the dimensional constraints of an electromagnetic single coil pickup as used in the priorAttorney Docket No. 38153.0002P1art to allow for replacement of the pickup without the need to modify the structure of the instrument body. The fidelity and output of the capacitive pickup assembly is related to the surface area available for the pickup plate and, therefore, in this regard, the single coil format may consequently have a reduced output compared to that of the larger twin coil humbucker format. A solution to this is the use of a “table” that is attached to the top surface of the capacitive pickup assembly that can accommodate an electret blade and pickup plate with larger dimensions in the direction of the instrument strings than would otherwise be possible.

[0151] Combination Electromagnetic Pickup and Capacitive Pickup.

[0152] In some optional aspects, the capacitive pickup assembly can include the use of a capacitive pickup and an electromagnetic pickup packaged in the same case using switches to mix the outputs of the two types of pickup thereby producing a wider range of possible outputs from a single pickup.

[0153] Use of Rechargeable Batteries

[0154] In some optional aspects, the capacitive pickup assembly can include an optional preamplifier circuit that is designed for optimal use at 9VDC but will operate with a voltage as low as 6V. This allows for use of 2 x CR2032 (3V) standard disposable 3V batteries or 2 x LIR20323.6V rechargeable batteries.

[0155] Use of Integrated USB Battery Charging Circuit

[0156] Another aspect of the disclosed capacitive pickup assembly includes the optional use of an integrated USB battery charging circuit. This allows recharging of rechargeable batteries via a USB connection and an integrated charging circuit and obviates the need for battery changes once they are depleted.

[0157] Battery Charge Status Indicator

[0158] In another exemplary aspect, the disclosed capacitive pickup assemblies can include a battery charge status indicator. In some exemplary aspects, a momentary switch or button can be added to the capacitive pickup assembly and attached to the external casing or pickup ring. When pressed, the switch or button can light an UED, also attached to the external casing, to indicate the charge status of the battery. In one exemplary aspect, the circuit can be designed to only light the UED if the battery charge is above a certain operating voltage. If the LEDAttorney Docket No. 38153.0002P1does not light when the button is pressed, it indicates the battery or batteries require replacement or recharging. Additional examples may dispense with the need for a momentary switch and to use timing circuitry to run the LED status check for the first few seconds after the power is applied to the preamplifier. This can save external space and component count.

[0159] Alternative Inner Case Door

[0160] In another exemplary aspect, the disclosed capacitive pickup assemblies can include use of an encased battery pack (not an on-board pack on the preamplifier PCB) that fits into a slot in the inner case lid. In this exemplary aspect, the preamplifier forms a separate component that is located in the space within the inner case.

[0161] Battery Access And Preamplifier Access

[0162] In another aspect, the disclosed capacitive pickup assemblies can provide easy access to the replacement batteries provided by the hinged lid on the internal case. (See, e.g., FIGS. 12-13 and 17-19). Once the instrument strings are slackened and the charge blade is removed, the inner case lid can be exposed. (See, e.g., FIG. 11). Once opened, the hinged lid allows access to the battery pack for replacement. The recessed top surface of the lid can also serve as the mounting surface for pickup foil. In some aspects, at least one of the internal preamplifier and battery supply can be accessed upon removing the retractable / removable charge blade.

[0163] Easy Preamplifier Replacement

[0164] In another aspect, the capacitive pickup assembly can allow for replacement of the optional preamplifier should the need arise. Once the inner case lid is opened, the preamplifier and battery subassembly can be exposed allowing the wire-to-board connections to be removed and the preamplifier to be replaced.

[0165] Capacitive Pickup with Analogue Simulation of Inductive Resonant Peak

[0166] From an analogue signal model perspective, an electromagnetic pickup is effectively a low-pass filter and a capacitive pickup as described here is effectively a high-pass filter. A low-pass filter is able to accurately “pass on” lower frequency signals generated by the instrument strings, but at a point in the frequency range, the ability to “pass on” the signals drops off dramatically, limiting higher frequency output. This generally happens in the rangeAttorney Docket No. 38153.0002P1from about 3-10Khz depending on a large number of physical characteristics of the pickup. Another feature of electromagnetic pickups is the resonant frequency peak caused by the interaction between the effective resistance, inductance, and capacitance components of the pickup “model.” This peak occurs approximately just before the point where the “low pass filter” starts to attenuate the higher frequencies. The result is a characteristic shape of an electromagnetic frequency response plot that displays a reasonably flat response until about 1kHz when the resonance starts to increase the output to a peak followed by a rapid decline and attenuation of the output at higher frequencies. Much effort goes into tuning an electromagnetic pickup to a specific frequency peak. This is what gives an electromagnetic pickup the “vintage” tone often defined as, “not flat,” “not hifi,” and strongly focused in the “mid-range”. When this peak is in the range from about 3-5kHz, the tone is described as having “bright,” “chime,” or “bell-like” character. With the peak in the range from about 1-3 kHz, the tone is described as “warm, thick with strong mid-range.”

[0167] The natural attenuation at high frequencies associated with electromagnetic pickups is useful when the signal is later distorted by external effects and amplifiers as is so often the case. This attenuation helps to limit the “brittle, unpleasant” nature of high frequencies when they are routed through distortion or overdrive effects before final amplification.

[0168] A capacitive pickup, by contrast, is effectively a high-pass filter. Such a filter is able to “pass-on” higher frequency signals accurately but at lower frequencies the signal is attenuated thereby limiting bass response. While an electromagnetic pickup is a low-pass filter and a capacitive pickup is a high pass filter, the key difference between the two is that there is no inductive element in the model of a capacitive pickup and therefore no magnetic inductive resonant peak. This gives capacitive pickups the characteristic output often called “clear, very bright, detailed, dynamic with good sustain.”

[0169] By altering the physical dimensions and characteristics of a capacitive pickup and using active electronics, it is possible to improve the low-frequency response to provide an almost flat curve across the audible range. The capacitive pickup consequently provides a very “true” reflection of how the instrument strings are vibrating without “interacting” with the strings in the way an electromagnetic pickup does. This gives the pickup its clarity and dynamics with little loss of harmonics.Attorney Docket No. 38153.0002P1

[0170] In some aspects, analogue electronics can be used to amplify the signal and to optionally insert an active fdter to simulate or mimic an electromagnetic pickup inductive vintage sound. For instance, in some optional aspects, it is contemplated that a capacitive pickup can model or mimic the inductive resonant frequency peak very closely so as to provide the characteristic tone of a “vintage” electromagnetic pickup while retaining the benefits of clarity, dynamic range and sustain (See, e.g., FIG. 23).

[0171] To enable this behavior, the disclosed capacitive pickup assembly can utilize active electronics with precise “tuning” that then simulates an inductive resonant peak and high frequency signal attenuation in a very similar manner to that found in electromagnetic pickups. The resonant peak characteristics are not inherent and can be tuned by careful component selection or by using adjustable controls within the signal chain.

[0172] In some aspects, it is contemplated that the ability to electronically simulate an inductive peak is a function that can be switched in and out of the signal chain providing the ability to switch between the clear, detailed voice of a capacitive pickup and the “vintage” tones of an electromagnetic pickup, while retaining the detail, dynamics, and sustain throughout. As an electromagnetic pickup has good bass response and inherently limited treble response, attempting to use active electronics to improve the high frequency response to match that of a capacitive pickup can be very challenging as these higher frequencies are not available in an electromagnetic pickup. In this exemplary aspect, an example capacitive pickup assembly is provided in FIG. 23, which can include, but is not limited to, an analogue signal conditioning chain that can comprise, but is not limited to comprising, the following elements:

[0173] (1 ) Sensor plate. The sensor plate provides the signal by detecting extremely small changes in capacitance generated by string motion.

[0174] (2) Input buffer and noise suppression. The input buffer isolates the signal source from later stages by providing very high input impedance and very low output impedance, ensuring the signal is passed on with little to no distortion.

[0175] (3) 1st Stage gain. The 1st gain stage provides initial signal amplification.

[0176] (4) Inductance simulator with a bypass switch. The simulated inductive filter can be included in or excluded from the signal chain using a bypass switch to provide tone options. This allows the use of a “clear” capacitive signal alone, or the inclusion of the inductanceAttorney Docket No. 38153.0002P1simulator to provide the “vintage” tones. Furthermore, two or more vintage options can be switched in or out to give various vintage tones as required.

[0177] (5) Inductance simulator with an optional “tunings ” selector switch. The simulated inductive filter can include a switch or switches to selectively choose between various “tunings” of the “vintage” inductive filter thereby providing the user with a range of tone options including the original capacitive tone.

[0178] (6) 2nd Stage gain. The 2nd stage application brings the signal up to expected instrument levels of a few hundred millivolts or more.

[0179] (7) Output buffer. The output buffer provides the low output impedance to drive subsequent stages or cables without causing signal distortion.

[0180] In further aspects, the 1ststage gain can be optional. In another example, a capacitive pickup assembly consistent with the present disclosure can comprise an input buffer, gain (optionally, a single gain stage), and an output buffer. In further optional aspects, the capacitive pickup assembly can include an inductance simulator.

[0181] In some aspects, the assembly can include a capacitive sensor plate that includes a corrugated surface. In some aspects, the corrugated sensor surface can increase surface area. Since capacitance is directly related to the surface area of the sensor plate, the capacitance and the resulting signal can be increased by including corrugations in the sensor surface.

[0182] In some aspects, the capacitive pickup assembly can include a mechanism to limit the effect of human body capacitance on the sensor and the resulting signal interference by including areas of the sensor selected to be less significant for detecting the signal from the vibrating strings and more significant for detecting the effect of human body capacitance. Using a differential amplifier, these two areas can provide two separate inputs to a differential amplifier which then output the full signal including that of the signal generated by the vibrating strings as well as the signal generated by the effect of human body capacitance. Then, the signal caused by the effect of human body capacitance is subtracted, resulting in a cleaner, less noisy signal. In some aspects, this approach can include detecting both the vibrating strings and the effects of human body capacitance, and finding the difference between the two inputs to arrive at just the musical signal.Attorney Docket No. 38153.0002P1

[0183] Exemplary Method of Use

[0184] Once the capacitive pickup assembly 1 has been properly mounted onto the stringed instrument 50 and the electric field has been established, one or more of the instrument strings 53 are then plucked or strummed and the vibrations so caused result in variations in the displacement between the oscillating strings (optionally, ferrous strings). These variations cause corresponding fluctuations in the electric field. The strings 53 act as one plate of a capacitor above the electret assembly (e.g., the electret charge blade 9), and the pickup sensing plate or foil 13 below the electret assembly begins acts as the opposite plate of the capacitor, thereby causing a variable voltage at the pickup sensing plate or foil 13 corresponding to the fluctuations in the electric field.

[0185] The frequency of the varying voltage is directly related to the frequency of the vibrations in the string 53, but the amplitude of the varying voltage at the pickup sensing plate or foil 13 is dependent on factors including, but not limited to : ( 1 ) the amplitude of the vibrating string / s; (2) the strength of the electric field; (3) the amount of overlap between the string / s 53 and the pickup sensing plate or foil 13; and (4) the permittivity of the dielectric electret material / s (including atmospheric air) placed between the instrument strings 53 and the pickup sensing plate or foil 13.

[0186] Experimental Results

[0187] Dynamic Range Response

[0188] One exemplary aspect of the capacitive pickup assembly is its exceptional ability to respond to wide dynamic range. Whether the instrument is played quietly or loudly with more attack, the pickup responds in a predictable way. The capacitive pickup excels in this regard when compared to other prior art electromagnetic pickups. As with many characteristics of the overall tone and output of the capacitive pickup, the effect is perceptible and most enjoyable when experienced in person.

[0189] Gain and Amplitude Response

[0190] FIG. 24 shows a comparison of the output (gain) of the capacitive pickup assembly compared to the output of a prior art electromagnetic pickup. The graph shows the pickup output plotted over time detected on three different microphones when a single chord is playedAttorney Docket No. 38153.0002P1on the instrument and allowed to fade. The graph compares a humbucker pickup (highlighted in blue) in the bridge position with the capacitive pickup assembly (highlighted in red) located in the neck position of a semi-acoustic guitar. Efforts were made to make the comparison as objective as possible.

[0191] Accordingly, some broad conclusions can be drawn. First, the amplitude of the signal from the capacitive pickup assembly is significantly stronger for most of the chord duration on all three channels. Second, the duration of signal (sustain) from the capacitive pickup assembly is significantly longer on two of the three microphone channels.

[0192] There are a number of possible reasons for this. First, the magnets used in an electromagnetic pickup will, by their very nature, dampen the strings vibrations due to the magnetic attraction between the strings and the magnetic pole pieces. Conversely, a capacitive pickup’s function does not rely on magnets and therefore will not impact the string vibrations. Second, signal strength is proportional to the length of the vibrating string that is interacting with the pickup sensing device. In magnetic pickups this length is limited to the size of the magnets while for the capacitive pickup assembly, the full size of the sensing plate is able to detect voltage variations generated by a significantly larger proportion of the overall string length. Thirdly, it should be noted the influence of the preamplifier gain would normally have a significant impact on the amplitude of the output. In the exemplary embodiment of FIG. 24, the preamplifier was configured to have unity gain, thereby limiting, as much as possible, the effect of signal amplification.

[0193] FIG. 25 shows the frequency spectrum graph for an electromagnetic pickup in the bridge position of a semi-acoustic guitar. This shows the accumulated frequencies and associated maximum gain captured for a piece of instrumental guitar music. For an electric guitar, the frequencies generally range from 40 Hz up to 5 kHz as is reflected in the x-axis of the graph. The white curve shows the average gain at the associated frequency and in this case the average gain is approximately half of the maximum gain. These results can be compared to FIG. 26.

[0194] FIG. 26 shows the frequency spectrum graph for a capacitive pickup assembly according to the implementations described herein, in the neck position of a semi-acoustic guitar as used in the frequency spectrum graph for FIG. 25. This shows the accumulated frequencies and associated maximum gain captured for the same piece of instrumental guitarAttorney Docket No. 38153.0002P1music as used in the frequency spectrum as for FIG. 25. The significant differences between the electromagnetic pickup and capacitive pickup assembly can be appreciated in the overall higher average gain for the capacitive pickup assembly, at all frequencies indicated by the white curve. There is a particularly large difference in the 200 to 500 Hz range, which accounts for the “warm” tones of the capacitive pickup assembly in the mid-ranges and similarly in the higher 5 kHz range the capacitive pickup assembly shows improvements over and above that shown for the electromagnetic pickup account for a “bright” characteristic in this higher range.

[0195] EXEMPLARY ASPECTS

[0196] In view of the described apparatus and methods, below are certain more particularly described aspects of the invention. These particularly recited aspects should not however be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein, or that the “particular” aspects are somehow limited in some way other than the inherent meanings of the language literally used therein.

[0197] Aspect 1: A capacitive electrostatic pickup assembly for detecting and amplifying the vibrations of a stringed musical instrument, wherein the pickup assembly comprises at least one electret material that forms a dielectric layer, and wherein the at least one electret material is configured to provide and maintain an electric field.

[0198] Aspect 2: The pickup assembly of aspect 1, further comprising a pickup plate or foil that is configured to detect the vibrations of the stringed musical instrument.

[0199] Aspect 3 : The pickup assembly of aspect 2, wherein the at least one electret material is a fixed plate mounted permanently within the pickup assembly.

[0200] Aspect 4 The pickup assembly of aspect 2, wherein the at least one electret material defines or is coupled to a retractable or removable blade or plate.

[0201] Aspect 5: The pickup assembly of aspect 3 or aspect 4, wherein the at least one electret material is configured to hold a quasi-permanent charge.

[0202] Aspect 6: The pickup assembly of aspect 3 or aspect 4, wherein the at least one electret material is configured to hold a charge generated using a triboelectric effect.Attorney Docket No. 38153.0002P1

[0203] Aspect 7 : The pickup assembly of aspect 6. wherein the at least one electret material consists of a single chargeable material.

[0204] Aspect 8 : The pickup assembly of aspect 6, wherein the at least one electret material comprises a composite material.

[0205] Aspect 9: The pickup assembly of aspect 8, wherein the composite material comprises a high-dielectric substrate material that defines one or more recesses configured to contain triboelectrically chargeable materials.

[0206] Aspect 10: The pickup assembly of aspect 9, wherein triboelectrically chargeable materials are disposed within the recess of the high-dielectric substrate material, thereby forming the composite material.

[0207] Aspect 11: The pickup assembly of any one of aspects 2-10, wherein the electric field is exclusively provided by the at least one electret material, and wherein the pickup plate or foil is a separate component from the at least one electret material.

[0208] Aspect 12: The pickup assembly of any one of the preceding aspects, further comprising an integrated preamplifier.

[0209] Aspect 13: The capacitive electrostatic pickup assembly of aspect 12, further comprising at least one switch that is configured to selectively cause the integrated preamplifier to apply a filter to modify a tone generated by the capacitive electrostatic pickup assembly.

[0210] Aspect 14: The capacitive electrostatic pickup assembly of aspect 13, wherein the at least one switch comprises a first switch that is configured to selectively cause the integrated preamplifier to selectively apply a simulated inductive filter.

[0211] Aspect 15: The capacitive electrostatic pickup assembly of aspect 14, wherein the simulated inductive filter is configured to mimic a vintage inductive filter.

[0212] Aspect 16: The capacitive electrostatic pickup assembly of any one ofthe preceding aspects, further comprising an internal DC power supply (e.g., a battery pack).

[0213] Aspect 17: The capacitive electrostatic pickup assembly of any one of aspects 1-15, further comprising an external DC power supply.Attorney Docket No. 38153.0002P1

[0214] Aspect 18: The capacitive electrostatic pickup assembly of any one of aspects 4-17, wherein the retractable or removable blade or plate is configured to provide access to the integrated preamplifier and a battery supply.

[0215] Aspect 19: The capacitive electrostatic pickup assembly of any one ofthe preceding spects, further comprising an electrically grounded metal casing, wherein the electrically grounded metal casing is configured to provide shielding from external electromagnetic interference.

[0216] Aspect 20: The capacitive electrostatic pickup assembly of aspect 19, further comprising an electrically conductive bridge that is configured to span above strings of the stringed instrument, wherein the electrically conductive bridge is electrically connected to the grounded metal casing, and wherein the electrically conductive bridge is configured to provide further shielding from electromagnetic interference.

[0217] Aspect 21: The capacitive electrostatic pickup assembly of aspect 20, wherein the electrically conductive bridge is selectively removable from the pickup assembly.

[0218] Aspect 22: A stringed musical instrument comprising:a body defining a compartment; andthe capacitive electrostatic pickup assembly of any one of the preceding aspects, wherein the capacitive electrostatic pickup assembly is received within the compartment.

[0219] Aspect 23: A method comprising:removing a first pickup assembly from a compartment of a body of a stringed musical instrument; andpositioning the capacitive electrostatic pickup assembly of any one of aspects 1-21 within the compartment.

[0220] Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the apparatus and methods described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

Attorney Docket No. 38153.0002P1CLAIMSWhat is claimed is:

1. A capacitive electrostatic pickup assembly for detecting and amplifying the vibrations of a stringed musical instrument,wherein the pickup assembly comprises at least one electret material that forms a dielectric layer, andwherein the at least one electret material is configured to provide and maintain an electric field.

2. The capacitive electrostatic pickup assembly of claim 1, further comprising a pickup plate or foil that is configured to detect the vibrations of the stringed musical instrument.

3. The capacitive electrostatic pickup assembly of claim 2, wherein the at least one electret material is a fixed plate mounted permanently within the pickup assembly.

4. The capacitive electrostatic pickup assembly of claim 2, wherein the at least one electret material defines or is coupled to a retractable or removable blade or plate.

5. The capacitive electrostatic pickup assembly of claim 3, wherein the at least one electret material is configured to hold a quasi-permanent charge.

6. The capacitive electrostatic pickup assembly of claim 3, wherein the at least one electret material is configured to hold a charge generated using a triboelectric effect.

7. The capacitive electrostatic pickup assembly of claim 6, wherein the at least one electret material consists of a single chargeable material.

8. The capacitive electrostatic pickup assembly of claim 6, wherein the at least one electret material comprises a composite material.

9. The capacitive electrostatic pickup assembly of claim 8, wherein the composite material comprises a high-dielectric substrate material that defines one or more recesses configured to contain triboelectrically chargeable materials.

10. The capacitive electrostatic pickup assembly of claim 9, wherein triboelectrically chargeable materials are disposed within the recess of the high-dielectric substrate material, thereby forming the composite material.Attorney Docket No. 38153.0002P111. The capacitive electrostatic pickup assembly claim 1, wherein the electric field is exclusively provided by the at least one electret material, and wherein the pickup plate or foil is a separate component from the at least one electret material.

12. The capacitive electrostatic pickup assembly of claim 1, further comprising an integrated preamplifier.

13. The capacitive electrostatic pickup assembly of claim 12, further comprising at least one switch that is configured to selectively cause the integrated preamplifier to apply a filter to modify a tone generated by the capacitive electrostatic pickup assembly.

14. The capacitive electrostatic pickup assembly of claim 13, wherein the at least one switch comprises a first switch that is configured to selectively cause the integrated preamplifier to selectively apply a simulated inductive filter.

15. The capacitive electrostatic pickup assembly of claim 14, wherein the simulated inductive filter is configured to mimic a vintage inductive filter.

16. The capacitive electrostatic pickup assembly of claim 1, further comprising an internal DC power supply.

17. The capacitive electrostatic pickup assembly of claim 1, further comprising an external DC power supply.

18. The capacitive electrostatic pickup assembly of claim 4, wherein the retractable or removable blade or plate is configured to provide access to the integrated preamplifier and a battery supply.

19. The capacitive electrostatic pickup assembly of claim 1, further comprising an electrically grounded metal casing, wherein the electrically grounded metal casing is configured to provide shielding from external electromagnetic interference.

20. The capacitive electrostatic pickup assembly of claim 19, further comprising an electrically conductive bridge that is configured to span above strings of the stringed instrument, wherein the electrically conductive bridge is electrically connected to the grounded metal casing, and wherein the electrically conductive bridge is configured to provide further shielding from electromagnetic interference.

21. The capacitive electrostatic pickup assembly of claim 20, wherein the electrically conductive bridge is selectively removable from the pickup assembly.Attorney Docket No. 38153.0002P122. A stringed musical instrument comprising:a body defining a compartment; andthe capacitive electrostatic pickup assembly of any one of the preceding claims, wherein the capacitive electrostatic pickup assembly is received within the compartment.

23. A method comprising:removing a first pickup assembly from a compartment of a body of a stringed musical instrument; andpositioning the capacitive electrostatic pickup assembly of any one of claims 1-21 within the compartment.

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