String Instrument Tone Control with Dual Potentiometers

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Solution Overview

Problem

Existing tone controls for string instruments do not provide an option for a natural, unfiltered sound without using a switch to bypass the tone control network, and they are prone to picking up ambient electromagnetic interference (EMI) due to their inductive qualities, resulting in unwanted 'hum' in amplified audio.

Innovation Solution

A tone control system that includes a pair of potentiometers mechanically coupled for concurrent travel, with filter capacitors in series, allowing for high pass, low pass, or unfiltered signal paths, and a high frequency bypass circuit that filters signals from pickup coils to cancel EMI, providing selective filtering and noise reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If traditional tone control networks with potentiometers and capacitors are used, then filtering control is provided, but a switch is required to bypass the network for unfiltered sound

Engineering Contradiction:

Improveaccess to unfiltered soundVSAvoidswitch requirement

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent employs a dynamic circuit configuration where the capacitor connection state changes continuously based on potentiometer position. At certain positions, the capacitor is connected to provide filtering; at other positions, it is disconnected to provide unfiltered sound. This dynamic reconfiguration eliminates the need for a separate bypass switch while maintaining full control over the filtering effect throughout the potentiometer's range of motion.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If magnetic pickups are used to convert string vibration into electrical signals, then sound detection is achieved, but ambient electromagnetic interference is picked up resulting in hum

Engineering Contradiction:

Improvestring vibration detectionVSAvoidelectromagnetic interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies feedback signaling that is out of phase with the pickup signal. This out-of-phase signal counteracts the electromagnetic interference (hum) picked up by the magnetic pickup, effectively canceling the harmful interference while preserving the desired string vibration detection capability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Power

If pickup coils are coupled in series to provide fuller sound, then sound strength is improved, but low pass filtering effect increases reducing high frequency response

Engineering Contradiction:

Improvesound strengthVSAvoidhigh frequency response

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the circuit configuration parameter by switching between series and parallel coupling of pickup coils based on the desired sound characteristics. Series coupling provides stronger output with low-pass filtering characteristics, while parallel coupling preserves high-frequency response. The system dynamically adjusts this parameter to maintain both sound strength and frequency response integrity as needed.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system allows for precise control over filtering, reducing ambient noise and enabling a natural, unfiltered sound by selectively positioning the potentiometer contacts and using a high frequency bypass circuit to cancel EMI, enhancing sound quality and reducing unwanted hum.

Implementation Method 1

a high pass filter is formed at one end of the concurrent mechanical travel

Methodology Applied

Scientific EffectHigh pass filter: Filter (electronic)

Implementation Method 2

a low pass filter is formed at an opposing end of the concurrent mechanical travel

Methodology Applied

Scientific EffectLow pass filter: Filter (electronic)

Implementation Method 3

The most commonly used pickups uses the principle of direct electromagnetic induction

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 4

a high frequency bypass circuit coupled in parallel with one of the pair of pickup coils for filtering signals from the pair of pickup coils

Methodology Applied

Scientific EffectHigh frequency bypass filtering: Filter (electronic)

Data Source

PatentUS9153218B1Tone control for string instruments

Publication Date: 2015.10.06 MICEK PETR

AI summary

A tone control for string instruments includes a pair of potentiometers each coupled in series relationship with a respective filter capacitor. The pair of potentiometers are mechanically coupled one to the other for concurrent mechanical travel of respective displaceable contacts thereof to provide selective filtering of one or more pick-up sensors of the instrument. Responsive to selective positioning of the displaceable contacts of the pair of potentiometers, signals input thereto are high pass filtered, low pass filtered or unfiltered. The tone control can serve as a master tone control where separate tone controls are connected to series coupled pairs of pickup coils and coupled to the master tone control through a blend configuration control.