Audio Gain Architecture for Noise-Free High Dynamic Range Capture
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Solution Overview
Problem
Conventional preamplifiers produce audible 'zipper' noise due to abrupt gain changes and have limited dynamic range, which is not fully captured by existing ADCs, especially when handling high dynamic range signals from microphones.
Innovation Solution
An audio processing system with an analog amplification stage having a fixed gain and dynamic range, matched by an ADC stage, and a digital gain stage allowing user-selectable gain adjustments in imperceptible steps to minimize noise and optimize signal capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital gain control is used with discrete steps (e.g., ±1dB), then variable gain adjustment is achieved, but audible clicks and zipper noise are produced during gain transitions
Solution Approach 1:
The patent replaces the mechanical/analog gain switching system with a digital gain control system. Instead of physically switching between discrete gain values which causes abrupt voltage changes and audible clicks, the system uses digital signal processing to apply gain adjustments. This substitution allows for smooth, continuous gain transitions that are imperceptible to the human ear, eliminating the zipper noise effect while maintaining full variable gain adjustability.
2Object-affected harmful factors
If the number of gain steps is increased to reduce step size, then audible clicks are reduced, but the number of resistors and switching system complexity increases
Solution Approach 1:
The patent eliminates the complex resistor network and mechanical switching system by replacing them with a digital gain control implementation. Instead of using multiple resistors and switches to create fine gain steps, the system uses digital processing to achieve smooth gain transitions. This approach dramatically reduces component count and circuit complexity while effectively eliminating audible clicks through imperceptible gain changes.
Solution Approach 2:
The patent extracts and removes the analog gain control circuitry (resistors, switches, and associated components) from the system. By taking out this complex hardware subsystem and replacing it with digital gain control, the invention simplifies the overall device architecture while achieving the desired reduction in audible clicks through software-based gain adjustment.
3Ease of manufacture
If ADC dynamic range does not match microphone dynamic range, then standard ADCs can be used, but high dynamic range signals are not fully captured
Solution Approach 1:
The patent implements a dynamic gain control system that adjusts the gain level based on the characteristics of the input signal. By dynamically varying the gain in response to signal levels, the system ensures that the full dynamic range of high-quality microphones is properly utilized and captured by standard ADCs. This dynamic adaptation allows optimal signal capture across varying input conditions without requiring specialized high-dynamic-range ADC hardware.
Data Source
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AI summary
An audio processing system is disclosed. The Audio processing system has an input for receiving a balanced analog audio signal; an analog amplification stage having a first fixed gain and a first dynamic range. It further includes an analog to digital conversion stage, having a second dynamic range that matches said first dynamic range of the analog amplification stage. A digital gain stage can also be provided to allow user selectable gain.