Hi,
DrCWO here is the amixer output you requested, this is for DAC8PRO firmware version 1.4 connected to a raspberry pi 4b on raspbian buster:
pi@raspberrypi:~ $ amixer -c 2 contents
numid=8,iface=CARD,name='Keep Interface'
; type=BOOLEAN,access=rw------,values=1
: values=off
numid=7,iface=CARD,name='OKTO RESEARCH Internal Clock Validity'
; type=BOOLEAN,access=r-------,values=1
: values=on
numid=3,iface=MIXER,name='DAC8PRO Playback Switch'
; type=BOOLEAN,access=rw------,values=8
: values=on,on,on,on,on,on,on,on
numid=4,iface=MIXER,name='DAC8PRO Playback Switch',index=1
; type=BOOLEAN,access=rw------,values=1
: values=on
numid=5,iface=MIXER,name='DAC8PRO Playback Volume'
; type=INTEGER,access=rw---R--,values=8,min=0,max=99,step=0
: values=99,99,99,99,99,99,99,99
| dBminmax-min=-99.00dB,max=0.00dB
numid=6,iface=MIXER,name='DAC8PRO Playback Volume',index=1
; type=INTEGER,access=rw---R--,values=1,min=0,max=99,step=0
: values=99
| dBminmax-min=-99.00dB,max=0.00dB
numid=2,iface=PCM,name='Capture Channel Map'
; type=INTEGER,access=r----R--,values=8,min=0,max=36,step=0
: values=0,0,0,0,0,0,0,0
| container
| chmap-fixed=FL,FR,FC,LFE,RL,RR,FLC,FRC
numid=1,iface=PCM,name='Playback Channel Map'
; type=INTEGER,access=r----R--,values=8,min=0,max=36,step=0
: values=3,4,7,8,5,6,12,13
| container
| chmap-fixed=FL,FR,FC,LFE,RL,RR,FLC,FRC
The play back volume value can be changed via amixer command but this does not match or affect the DAC8PRO volume setting. Not sure this is normal ? I have not used amixer volume control before and am not very familiar with ALSA, is the amixer volume control separate from the USB DAC volume control setting ?
Volume control via usb would be very convenient.