←back to thread

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

(jamesbvaughan.com)
287 points jamesbvaughan | 5 comments | 25 Jul 24 15:11 UTC | HN request time: 0.961s | source
Show context
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. jamesbvaughan ◴[27 Jul 24 00:05 UTC] No.41083455[source]▶
In this case, I was using the optical out from a WiiM mini into a Yamaha amp. I don't know much about digital audio, but I know that I was able to control the volume of the WiiM's digital output with that setup.

On the other hand, I use a Schiit Asgard at my desk, where I have it connected to my Mac via USB-C. In that setup, I have no control over the volume level going in to the Asgard. MacOS just disables the software volume control when I'm using that audio output.

replies(1): >>41083849 #
2. rahimnathwani ◴[27 Jul 24 01:29 UTC] No.41083849[source]▶
I think for a WiiM mini to control the volume on the digital output, it would need to scale down every sample. This is probably fine over some range (it has a 24 bit output, so putting the volume at two thirds, would still result in 16 bits, the same as CD). But I'm curious what would happen at very low volumes, e.g. if you're down to only 4 bits.
replies(2): >>41083909 #>>41089892 #
3. mattclarkdotnet ◴[27 Jul 24 01:46 UTC] No.41083909[source]▶
Each bit is ~6dB, so 2/3 perceived volume is still 23 bits. 8 bits is 48dB, which is less than 1% of the original volume, and still using 16 bits
replies(1): >>41083937 #
4. TylerE ◴[27 Jul 24 01:54 UTC] No.41083937{3}[source]▶
And this is why all computer audio should be 24 bit internally. A lot of the newer pro apps are actually using 32 bit floats
5. rahimnathwani ◴[27 Jul 24 22:49 UTC] No.41089892[source]▶
Too late to edit my original comments. I am clearly mistaken about the relationship between amplitude and perceived loudness.