multichannel audio -- four out of 16 channels turned off by default

[jyrkialakuijala]

I'm using UMC1820 and Behringer ultragain digital to have 16 channels of output. I need to use them in 48000/24 bit to use all channels, 96000 can only use 12 channels.

It used to work well in early 2023. There was (likely) a software update around mid 2023 that turned off four channels automatically.

I was able to fix it by issuing commands:

$ amixer --card 2 cset numid=3,iface=MIXER,name='UMC1820 Output Playback Volume' 127,127,127,127,127,127,127,127,127,127,127,127,127,127,127,127

$ amixer --card 2 cset numid=1,iface=MIXER,name='UMC1820 Output Playback Switch' on,on,on,on,on,on,on,on,on,on,on,on,on,on,on,on

When I turned the audio device (UMC1820) off and back on, then I need to reissue those commands to have all 16 channels in use.

It was not easy to understand what was going on, it could have been a failure in the amplifier, line transformers, the ultragain box -- but turned out to be software config. When I looked at software configs I was first convinced that it was configured to 96000 rate because that also creates the same effect of only four channels being available on the extension box.

It would be nice if the devices were detected properly and all channels would be on by default, not just 12 first channels.