USB-C PD powered phono preamplifier

Abstract

The phono preamplifier, which processes the audio output signal from the turntable, is powered by a variable voltage adapter, such as a USB-C to PD power adapter.

Description

[Background technology]

[0001] This application claims priority to U.S. patent application 17 / 574,063, filed January 12, 2022, entitled "USB-C PD POWERED PHONO PREAMPLIFER," which is incorporated herein by reference.

[0002] Consumers have limited availability of high-resolution digital audio (audio files with sample rates above 48 kHz or audio bit depths above 16 bits). Lenbrook Industries Limited (owner of NAD Electronics and Bluesound Music Systems and applicant of the present application) began developing a new type of high-resolution media audio playback system in 2004 and demonstrated the system in 2009. By 2011, the NAD Masters Digital Suite Home Sound System enabled consumers to experience music using one or more networked playback devices. The system's BluOS operating system was expanded to more affordable devices with the introduction of the Bluesound brand in 2012. Through a software control application installed on a controller (e.g., IR remote, wall controller, smartphone, tablet, computer, voice input device), consumers can play what they want in any room with a networked playback device. High-resolution music files can be accessed in each room with a playback device and in groups of rooms that play the same music together in sync. The BluOS modular software design also enables standardization of Audio Video Receiver (AVR) devices, lowering the cost of software development compared to the highly proprietary MCU / DSP software currently used across the AVR industry.

[0003] This application relates generally to phonograph (phono) preamplifiers, and more specifically to a USB-C PD-powered phono preamplifier connected to a local area network (LAN).

[0004] The phonograph audio playback device was one of the most important inventions of the 20th century. Although most music is enjoyed in digital audio format through mobile devices, the phonograph "turntable" remains extremely popular among music collectors and other forward-thinking consumers who recognize the authentic listening experience that a turntable provides. Many of the world's most successful music recordings were originally recorded and mastered for playback on a vinyl turntable. While digital reissues available on CDs and music streaming services allow users to easily enjoy these recordings, many maintain that the original vinyl copies are perceived to be superior. This has spawned a revival of classic albums reissued on high quality vinyl, and occasionally online sales of original vinyl copies that are recognized as representing the record company's best vinyl issue or "imprint." Audiophiles and collectors also have a wide selection of vinyl playback hardware to choose from. This includes newly manufactured turntables and diamond styluses available from established and emerging equipment brands.

[0005] High quality turntables still require specialized processing of their output signal before audio power amplification is applied to drive large loudspeakers. This processing step is performed by a phono preamplifier and includes high gain amplification and standardized frequency equalization. The phono preamplifier effectively conditions the small electrical signal of the turntable's magnetically coupled diamond stylus. The large signal gain and frequency equalization curve of the phono preamplifier present difficult technical challenges.

[0006] If attention is not paid to the quality of the preamp power supply, the small turntable music signal is easily overrun by electrical noise. Also, the high dynamic range of the turntable music signal, together with the frequency equalization of the circuit, requires a relatively high voltage to be supplied to the preamp circuit. This voltage level provides enough "headroom" to prevent saturation during loud music passages, which can damage expensive audio power amplifiers and speakers. If a high performance phono preamp is the goal, a low noise, high voltage power supply will represent the most costly part of the phono preamp device. The best phono preamp devices currently on the market employ traditional "linear" power supplies to minimize electrical noise compared to modern switch mode power supplies. High-end phono preamp devices come with a costly dedicated external linear power adapter, usually with a minimum voltage of 12VDC. This powers the operational amplifier ("op amp") circuitry inside the phono preamp device. This circuit applies the gain and "RIAA" standard phono equalization curve, first specified in the recording industry.

[0007] It was simply not possible to reduce costs on the above circuitry without compromising the final audio listening quality. The cost explains why most consumer electronics manufacturers began removing the phono preamp feature from their products in the late 1980s as the widespread popularity of vinyl waned. In the 2000s low-cost USB external power adapter devices became available, but these did not lend themselves to high-quality phono preamplifiers due to their low output voltage and digital switching noise. The voltage and noise issues of USB 2.0 power supplies could be addressed with additional switch-mode voltage boost and linear regulation, but this would erase the desired cost savings. Summary of the Invention

[0008] According to one or more aspects, a phono preamplifier powered by a variable voltage adapter for processing an audio output signal from a turntable is disclosed. The phono preamplifier includes an audio input port connected to the turntable by a cable for receiving the audio output signal from the turntable. A power input port of the phono preamplifier is connected to the variable voltage adapter by a cable for receiving power from the variable voltage adapter. A power controller subsystem is connected to the power input port to manage the power received at the power input port. A microprocessor subsystem is connected to the power controller subsystem to control operation of the power controller subsystem. An operational amplifier circuit is connected to the audio input port and to the power controller subsystem for amplifying and conditioning the audio output signal from the turntable. An analog-to-digital converter (ADC) is connected to the operational amplifier circuit for converting the amplified and conditioned audio output signal from the operational amplifier circuit to a digital bitstream output. The microprocessor subsystem is connected to the analog-to-digital converter to receive and process the digital bitstream output for transmission over a wired or wireless network for playback on one or more speaker devices.

[0009] In one or more embodiments, the variable voltage adapter comprises a USB-C powered device power adapter.

[0010] In one or more embodiments, an op-amp power circuit is connected to the power controller subsystem and the operational amplifier circuit. The op-amp power circuit is configured to split the output voltage of power received from the power controller subsystem into two power rails of equal voltage but opposite polarity to power the operational amplifier circuit. In one or more embodiments, the output voltage is 12VDC and the two equal power rails comprise ±6VDC rails.

[0011] In one or more embodiments, the operational amplifier circuit performs high gain amplification and standardized frequency equalization on the audio output signal from the turntable.

[0012] In one or more embodiments, the variable voltage adapter powers the phono preamplifier with an output voltage high enough to reduce the effects of electrical noise and prevent saturation during loud music passages.

[0013] In one or more embodiments, the variable voltage adapter includes a switched mode power supply circuit.

[0014] In one or more embodiments, the microprocessor subsystem configures the power controller subsystem to request 12VDC voltage from the variable voltage adapter.

[0015] In one or more other aspects, a method is disclosed for powering a phono preamplifier that processes an audio output signal from a turntable using a variable voltage adapter, the method including receiving an audio output signal from the turntable, receiving power from the variable voltage adapter, managing the power from the variable voltage adapter, amplifying and conditioning the audio output signal from the turntable using power from the variable voltage adapter, converting the amplified and conditioned audio output signal into a digital bitstream output, and processing the digital bitstream output for transmission over a wired or wireless network for playback on one or more speaker devices. [Brief description of the drawings]

[0016] [Figure 1A] 1 illustrates a USB-C PD powered phono preamplifier according to one or more embodiments. [Figure 1B] 1 illustrates a USB-C PD powered phono preamplifier according to one or more embodiments.

[0017] [Diagram 2] FIG. 1 is a block diagram illustrating connections for a USB-C PD-powered phono preamplifier in a sound system in accordance with one or more embodiments.

[0018] [Diagram 3] FIG. 1 is a block diagram illustrating the system architecture of a USB-C PD-powered phono preamplifier according to one or more embodiments.

[0019] [Figure 4] FIG. 2 is a circuit diagram illustrating an op-amp power circuit of a USB-C PD powered phono preamp according to one or more embodiments.

[0020] Similar or identical reference numbers are used to identify common or similar elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Various embodiments disclosed herein relate to a phono preamplifier for processing an audio output signal from a turntable powered by a variable voltage adapter, such as a USB-C PD ("Powered Device") power adapter.

[0022] Recently, USB-C PD power adapters have become available. Because they follow industry standard specifications, many manufacturers are able to produce USB-C PD adapters in large quantities and at a lower cost than traditional linear power adapters commonly used in high-end phono preamplifier devices. USB-C PD adapter devices can deliver significantly more power and higher voltages than their USB 2.0 predecessors. USB-C PD supports variable output voltages. Voltage levels can be set as high as 12VDC via software negotiation with the device it is powering. USB-C PD standard power supplies can be used to reduce costs without compromising audio performance. Newer USB-C PD supplies use more modern switched-mode power circuitry than previous USB 2.0 generations, and devices according to embodiments are designed to substantially reduce or eliminate the switch-mode power noise of USB-C PD devices.

[0023] 1A illustrates a USB-C PD-powered phono preamplifier 100 in accordance with one or more embodiments. FIG. 1B shows certain internal components of preamplifier 100.

[0024] 2 is a block diagram illustrating the connection of a USB-C PD powered phono preamplifier 100 in a sound system in accordance with one or more embodiments. The phono preamplifier 100 is powered by a USB-C PD power adapter 102. It receives an audio output signal from a turntable 104 and amplifies and conditions the audio signal. The processed audio signal is then transmitted by the phono preamplifier 100 over a wired or wireless network for playback on one or more speaker devices 106.

[0025] FIG. 3 is a block diagram illustrating the system architecture of a USB-C PD powered phono preamplifier 100 according to one or more embodiments. The phono preamplifier 100 includes an electrical circuit board assembly 108 that is powered by a USB-C PD power adapter 102. The circuit board assembly 108 includes a dedicated USB-C power controller chip 110 and a microprocessor module 112 that runs software. The microprocessor software communicates with the USB-C PD power controller chip 110. A USB-C socket 114 on the circuit board allows for the connection of a standard USB-C PD external power adapter 102. When the external power adapter 102 is connected, the USB-C PD power controller chip 110 notifies the microprocessor software. The software then configures the power controller chip 110 to request 12VDC voltage from the external power adapter 102.

[0026] The power controller chip 110 notifies the microcontroller software that 12VDC has been identified as available from the USB-C PD external power adapter 102. The 12VDC power is applied to a dedicated op-amp power circuit 116, where a single resistor splits the 12VDC into two equal power rails. This effectively provides the op-amp with a split ±6VDC rail to operate it at optimal signal performance. Other electronic component values ​​connected to the op-amp allow the op-amp to apply gain and frequency equalization to the input turntable signal received at port 120. The conditioned audio output signal is applied to the input of a high quality analog-to-digital converter (ADC) 118. The microprocessor 112 receives the digital bitstream output of the analog-to-digital converter 118 for transmission over a wired or wireless LAN to which the phono preamp device 100 is connected. The digital bitstream is output to a wired network via a network port of the phono preamplifier (e.g., Ethernet port 122 - FIG. 1B) or to a wireless network via a wireless network interface of the phono preamplifier 100 (e.g., WiFi module 124 - FIG. 3). In one or more embodiments, the phono preamplifier 100 does not include other audio outputs.

[0027] In the illustrated embodiment, the USB-C PD powered phono preamp 100 comprises a separate device from the turntable 104. In one or more alternative embodiments, the USB-C PD powered phono preamp 100 is contained within the housing of the turntable 104.

[0028] Although several embodiments have been illustrated and described above, it is obvious that various changes, modifications, and improvements can be easily made by those skilled in the art. Such changes, modifications, and improvements are intended to be part of this disclosure and are intended to be within the spirit and scope of this disclosure. Although some examples presented herein include specific combinations of functions and structural elements, it is understood that the functions and elements may be combined in other ways in accordance with this disclosure to achieve the same or different purposes. In particular, acts, elements, and characteristics described in the context of one embodiment are not intended to be excluded from similar or different roles in other embodiments. Furthermore, the elements and components described herein may be further divided into additional components or combined to form fewer components to perform the same functions.

[0029] Accordingly, the foregoing description and accompanying drawings are by way of example only and are not intended as limiting.

Claims

1. 1. A phono preamplifier powered by a variable voltage adapter for processing an audio output signal from a turntable, comprising: an audio input port configured to be connected by a cable to the turntable for receiving an audio output signal from the turntable; a power input port configured to be connected to the variable voltage adapter by a cable to receive power from the variable voltage adapter; a power controller subsystem coupled to the power input port and configured to manage power received at the power input port; a microprocessor subsystem coupled to said power controller subsystem for controlling operation of said power controller subsystem; an operational amplifier circuit coupled to the audio input port and to the power controller subsystem for amplifying and conditioning an audio output signal from the turntable; an analog-to-digital converter coupled to the operational amplifier circuit for converting an amplified and conditioned audio output signal from the operational amplifier circuit into a digital bitstream output; The microprocessor subsystem is connected to the analog-to-digital converter and receives and processes the digital bitstream output for transmission over a wired or wireless network for playback on one or more speaker devices.

2. The phono preamplifier of claim 1 , wherein the variable voltage adapter comprises a USB-C powered device power adapter.

3. an op amp power circuit coupled to the power controller subsystem and to the operational amplifier circuit; 2. The phono preamplifier of claim 1, wherein the op-amp power circuit is configured to split the output voltage of power received from the power controller subsystem into two power rails of equal voltage but opposite polarity to power the operational amplifier circuit.

4. 4. The phono preamplifier of claim 3, wherein said output voltage is 12 VDC and said two equal power rails comprise ±6 VDC rails.

5. 2. The phono preamplifier of claim 1, wherein the operational amplifier circuit performs high gain amplification and standardized frequency equalization on an audio output signal from the turntable.

6. 10. The phono preamplifier of claim 1, wherein the variable voltage adapter powers the phono preamplifier with an output voltage high enough to reduce the effects of electrical noise and prevent saturation during loud music passages.

7. The phono preamplifier of claim 6 , wherein the variable voltage adapter powers the phono preamplifier with an output voltage of 12 VDC.

8. The phono preamplifier of claim 1 , wherein the variable voltage adapter includes a switched mode power supply circuit.

9. 2. The phono preamplifier of claim 1, wherein said microprocessor subsystem configures said power controller subsystem to request 12 VDC voltage from said variable voltage adapter.

10. The phono preamplifier of claim 1 , wherein the phono preamplifier is integrated into a housing of the turntable.

11. 2. A phono preamplifier as described in claim 1, wherein the phono preamplifier outputs the digital bit stream to a wired network via a network port of the phono preamplifier or to a wireless network via a wireless network interface of the phono preamplifier, and the phono preamplifier does not include other audio outputs.

12. 1. A method for powering a phono preamplifier for processing an audio output signal from a turntable using a variable voltage adapter, comprising: receiving an audio output signal from the turntable; receiving power from the variable voltage adapter; managing power from the variable voltage adapter; amplifying and conditioning an audio output signal from the turntable using power from the variable voltage adapter; converting the amplified and conditioned audio output signal into a digital bitstream output; and processing the digital bitstream output for transmission over a wired or wireless network for playback on one or more speaker devices.

13. The method of claim 12 , wherein the variable voltage adapter comprises a USB-C powered device power adapter.

14. 13. The method of claim 12, further comprising splitting an output voltage of power received from the variable voltage adapter into two power rails of equal voltage but opposite polarity to power an operational amplifier circuit for amplifying and conditioning the audio output signal.

15. 15. The method of claim 14, wherein the output voltage is 12 VDC and the two identical power rails comprise ±6 VDC rails.

16. 13. The method of claim 12, wherein the step of amplifying and conditioning the audio output signal includes performing high gain amplification and standardized frequency equalization on the audio output signal from the turntable.

17. 13. The method of claim 12, wherein the variable voltage adapter provides power at an output voltage high enough to reduce the effects of electrical noise and prevent saturation during loud music passages.

18. 20. The method of claim 17, wherein the variable voltage adapter provides power at an output voltage of 12VDC.

19. The method of claim 12 , wherein the variable voltage adapter comprises a switched mode power supply circuit.

20. The method of claim 12 further comprising the step of negotiating a voltage level of power received from the variable voltage adapter.

21. A USB-C / PD powered phono preamplifier for processing an audio output signal from a turntable, an audio input port configured to be connected to the turntable by a cable for receiving an audio output signal from the turntable; a power input port configured to be connected by a cable to a USB-C power device adapter for receiving power from the USB-C power device adapter; a power controller subsystem coupled to the power input port and configured to manage power received at the power input port; a microprocessor subsystem coupled to said power controller subsystem for controlling operation of said power controller subsystem; an operational amplifier circuit coupled to the audio input port and to the power controller subsystem for amplifying and conditioning an audio output signal from the turntable; an analog-to-digital converter coupled to the operational amplifier circuit for converting an amplified and conditioned audio output signal from the operational amplifier circuit into a digital bitstream output; The microprocessor subsystem is connected to the analog-to-digital converter and receives and processes the digital bitstream output for transmission over a wired or wireless network for playback on one or more speaker devices. A USB-C PD powered phono preamplifier.

22. an op amp power circuit coupled to the power controller subsystem and to the operational amplifier circuit; 22. The USB-C PD powered phono preamp of claim 21, wherein the op-amp power circuit is configured to split the output voltage of power received from the power controller subsystem into two power rails of equal voltage but opposite polarity to power the operational amplifier circuit.

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