Bugzilla – Bug 149
"Digital output level is fixed" loses (3.5 mm) analog output after volume change
Last modified: 2011-03-16 04:18:46 UTC
When I set "Digital Volume Control" to "Digital output level is fixed", I don't get any more audio on the 3.5 mm plug (did not test this on the cinch plugs) as soon as I change the volume. When I set it to "Volume Controls adjust digital outputs" *and* then change the volume, I get the audio back. (This is with the CVS version, i.e. squeezebox firmware version 6.) The packets all look normal (but then I don't have software to analyze them in detail) in both cases, as does the VFD display. Everything works in both cases, just the audio is mute in the "fixed" case (and yes, I tried setting the mute control on and off). This bug probably has been this way for a couple of weeks. Until today I had to use my old 5.0.1 server to get any output; I just found the workaround (set "Volume Controls adjust digital output") only today. Of course, I'm not sure this is a firmware problem, but this sounds like a reasonable guess.
Not fixed in firmware version 7 (*if* it is a firmware bug...).
The bug has been explained on the mailing list: Stephen R Ward says: "I'm using the twin phono sockets [...] after turning the volume up all the way to 40 [...] there is definitely an improvement in sound quality: [...] the volume seems to increase _exponentially_ from nothing somewhere in the low 30s, to full whack at 40[...] So the bug seems to be on the line jacks, too, and what I have been seeing seems to be related to the fact that I typically leave the volume setting around 20. Sean Adams says: "The analog volume level curve is whacked in this mode. Sorry - it's on my (long) list. Actually what we might need for this mode is a couple different curves for headphones vs speakers and also a min/max range limit."
fixed. just removed the **2 The levels sound "right" now for headphones. Should also be ideal for a fixel level amp.
Since firmware versions are pretty much meaningless by now: MD5 (squeezebox.bin) = f63140aecc309a5d514c49ef6812c21b This is the 2004-02-21 nightly. I can't say the levels are right for an amplifier. I still need to go to at least 27 to hear anything. 34 is about right. If I go to "volume controls adjust digital outputs", 18 is about the same level. (I typically stay around 20 to have enough adjustment headroom, so I don't hear anything when switching "digital output is fixed".) Maybe part of the bug is in "volume controls adjust digital outputs" now, as the volume does not really change that much between 20 and 40. I will consider this bug completely fixed if both settings ("digital output is fixed" and "volume controls adjust digital outputs") result in roughly the same output at the 3.5 mm jack over the range of volume settings. Ideally, the values from 0 to 27 should continue to be useful. I have lowered the priority, as this is not a blocker.
I just swapped out a SLIMP3 with a Squeezebox, set to "digital output level is fixed". I needed to change the volume from 20 (SLIMP3) to 38. This means that there essentially is no way to change the volume from the web interface any more. I continue to believe the level curve should be closer to that of the SLIMP3 and that of "Volume Controls adjust digital output".
Sean, does this depend on the amplifier or are the levels that out of whack?
In Firmware 39, the new effect is: The volume changes a lot between 0 and 10, a little between 10 and 20, and not very much between 20 and 40. I haven't measured this, but I'd say the perceptual loudness doubles between 5 and 10, between 10 and 20, and between 20 and 40. One would expect it to double at approximately equidistant points (say, 0 to 8, 8 to 16, 16 to 32, 32 to 40; this would cover about 50 dB, IIRC). The points certainly seem more like this for the digital adjustment. I've changed this to a P4, because it is almost good enough now.
We'll have to live with it as is.