Volume control (digital vs analog)
TL;DR
Analog volume controls (potentiometers) attenuate the analog signal after amplification - can add channel imbalance at low volumes. Digital volume controls attenuate before DAC conversion - perfect channel matching but can reduce effective bit depth at low settings.
Volume control in modern audio comes in two flavors, each with trade-offs.
Analog volume (traditional potentiometer)
- Physical resistor that varies to attenuate the signal after gain stages
- Simple, no bit-depth loss
- Cheap pots have channel imbalance at low volume (one channel louder than other)
- Premium pots (Alps RK27, TKD) are quiet and well-matched
Digital volume (DAC-side attenuation)
- Signal attenuated in the digital domain before D/A conversion
- Perfect channel matching (mathematical)
- Can reduce effective bit depth at very low volume – a 24-bit source at -60 dB volume effectively becomes 14-bit
- Not a problem in practice unless you listen at ultra-low volumes
Modern hybrid
Some DACs (ESS Sabre chips) use “hybrid” – digital control of an analog attenuator. Best of both worlds. The AIYIMA A80‘s digital volume implementation is well-designed and channel-matched.
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