Audio Gain Partitioning for Dynamic Range and Low-Noise Mixing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing personal audio devices face limitations in dynamic range and total harmonic distortion (THD+N) due to the application of gain and mixing within the number of available bits of the digital signal, which restricts high-quality audio playback and introduces noise when handling multiple audio streams.
Innovation Solution
An apparatus and method that involve separate digital gain paths for different audio signals, followed by conversion to the analogue domain and application of an analogue gain, with the control circuit determining the analogue gain based on the combination of digital audio signals to compensate for the gains applied, thereby enhancing dynamic range and trading off when necessary to improve noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital gain is applied to increase signal amplitude before conversion, then dynamic range is improved, but noise increases monotonically with gain
Solution Approach 1:
The audio signal processing is divided into separate digital and analogue gain stages. Digital gain is applied selectively to specific audio streams (music, system sounds) before DAC conversion, while analogue gain is applied to the combined signal after conversion. This segmentation allows optimal noise performance for each stage.
Solution Approach 2:
Different gain control strategies are applied to different audio streams based on their characteristics. Music signals receive digital gain to maximize dynamic range, while system sounds are handled with analogue gain to avoid quantization noise. The control circuit dynamically adjusts gain distribution based on the active audio streams.
2Device complexity
If multiple audio streams are mixed in the digital domain with gain application, then system complexity is reduced, but total harmonic distortion and dynamic range are limited by available bits
Solution Approach 1:
The audio processing architecture is segmented into separate digital gain paths for different audio streams (music, system sounds) before they are combined. This allows each stream to be processed with appropriate precision and dynamic range before conversion to analogue domain, avoiding the bit-depth limitations of digital mixing.
Solution Approach 2:
The digital-to-analogue converter acts as an intermediary that separates the digital gain stage from the final analogue mixing. By converting individual streams or selectively amplified streams to analogue before combination, the system avoids digital quantization errors that would occur with high-precision digital mixing of multiple streams.
3Measurement precision
If high gain is applied to the power amplifier to increase dynamic range, then the largest signal values are improved, but noise effectively masks lower-intensity audio signals
Solution Approach 1:
Digital gain is applied preliminarily to specific audio streams before they are converted to analogue domain. This preliminary amplification in the digital domain allows the signal to be converted with better signal-to-noise ratio, and the subsequent analogue gain can be reduced, preventing noise masking of lower-intensity signals.
Solution Approach 2:
The system dynamically changes the gain parameter distribution between digital and analogue domains based on the active audio streams. When music is playing alone, digital gain is increased for maximum dynamic range. When system sounds are mixed in, the control circuit adjusts to reduce digital gain and increase analogue gain, maintaining optimal noise performance across different operating conditions.
Data Source
AI summary
There is provided an apparatus for providing an output signal to an audio transducer, comprising: a first signal path for receiving a first digital audio input signal, applying a first digital gain, and outputting an amplified first digital audio input signal; a second signal path, for receiving a second digital audio input signal, applying a second digital gain, and outputting an amplified second digital audio input signal; converter circuitry, coupled to the first and second signal paths, for converting at least the amplified first and second digital audio input signals into the analogue domain, and outputting an analogue audio input signal; and an analogue gain element, for applying an analogue gain to the analogue audio input signal and outputting the output signal. The apparatus further comprises a control circuit, coupled to the first and second signal paths, operative to select the analogue gain based on a combination of at least the first and second digital audio input signals or signals derived therefrom, and to select the first and second digital gains so as to compensate for the analogue gain.