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Reverse-engineering my speakers' API to get reasonable volume control

(jamesbvaughan.com)
287 points jamesbvaughan | 2 comments | 25 Jul 24 15:11 UTC | HN request time: 0.411s | source
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rahimnathwani ◴[26 Jul 24 23:52 UTC] No.41083383[source]▶
I know it is tangential, but this about his old system caught my attention:

  With that system, I could set the amplifier’s analog volume knob such that the max volume out of the streamer corresponded to my actual maximum preferred listening volume, giving me access to the full range of Spotify or AirPlay’s volume controls.
Assuming an analog input, this might result in a noticable quality reduction at low volumes.
replies(3): >>41083455 #>>41083487 #>>41083495 #
1. hunter2_ ◴[27 Jul 24 00:10 UTC] No.41083487[source]▶
Reducing excessively before the DAC and high gain after the DAC is far more likely to result in quality reduction, due to quantization error. Having reasonable levels before the DAC and just the right amount of gain after the DAC (e.g., via an amplifier's attenuator setting) is the best possible scenario. So TFA's prior setup may have been superior in this regard, depending on how the digital volume control on the new speakers is implemented (i.e., before the DAC, or as a VCA after the DAC).

Where this breaks down is if the analog signal path (after the DAC) consists of something noisy after the attenuator. Passive attenuation (like built into an amp, or the master fader of a mixer, etc.) won't add noise, but something active like an outboard EQ would. The attenuation to set desired max level must be completely last (before power amp) to avoid noise.

replies(1): >>41083753 #
2. jeffbee ◴[27 Jul 24 01:06 UTC] No.41083753[source]▶
We really don't want to be touching the digital signal. The state of the art is to change the DAC reference level, putting the DAC output at the sweet spot for the analog stage for any given ultimate output level.