Differential Microphone Amplifier With Output-Level Distortion Control
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Solution Overview
Problem
Existing amplification systems for microphone signals introduce distortion that is dependent on the input signal level, making it challenging to achieve a controllable degree of distortion across varying signal levels, such as those from microphones near drums versus those capturing ambient sounds.
Innovation Solution
A method involving a differential amplifier with a negative feedback path and non-linear circuitry to introduce distortion, where the degree of distortion is controlled based on the output signal level rather than the input signal level, using a combination of bipolar transistors and field effect transistors with constant current sources and operational amplifiers to manage gain and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If overloading the input stages of the amplifier is used to introduce distortion, then distortion can be introduced, but the distortion level becomes dependent on the input signal level, making it impossible to achieve controllable distortion across varying signal levels
Solution Approach 1:
The patent introduces a signal level detection mechanism that acts as an intermediary between the input signal and the distortion introduction process. The system detects the input signal level and uses this information to control the distortion amount, decoupling the distortion control from direct input signal dependence. This allows the distortion level to be managed independently of the varying input signal levels from different microphone positions and sources.
Solution Approach 2:
The patent implements a feedback mechanism where the input signal level is continuously monitored and this information is fed back to adjust the distortion introduction. By using the detected signal level to modulate the distortion amount, the system maintains consistent distortion characteristics across varying input levels, resolving the contradiction between controllability and independence from input signal level.
2Reliability
If early amplification systems with non-linear elements are used, then even harmonic distortion can be introduced which is musically desirable, but the distortion cannot be controlled independently of the input signal level
Solution Approach 1:
The patent employs dynamic control of the distortion amount based on the detected input signal level. The system continuously adapts the distortion introduction to match the current signal level, ensuring that musically desirable even harmonic distortion is maintained while providing independent control. This dynamic adjustment resolves the contradiction by allowing the distortion quality to remain reliable while making it controllable through the signal level detection mechanism.
Data Source
AI summary
A method of amplifying an output signal from a microphone or audio transducer so as to introduce a controllable degree of distortion for inputs having a wide dynamic range, comprising the steps of: receiving a differential input signal from a microphone or audio transducer, applying said differential signal to a differential amplifier, said differential amplifier having a negative feedback path to control the gain of said amplifier; and providing non-linear circuitry in said feedback path so as to introduce distortion, such that the degree of distortion present is related to the level of the output signal and not to the level of the input signal.