Since I asked the question and figured it out myself, I might as well answer it (see below). While I don’t think anyone cares for the answer in itself, the reason I needed the answer might interest some. This solution allows me to create a bit-perfect volume control for my hifi-amplifier. All it requires is the Roon Endpoint running on Linux and an amplifier that is actually controllable via RS232/i2c/network.
I posted a bit more information in the Linux forum.
[HOWTO] how to create a bit perfect volume control for your amplifier in Roon – guide
Kind regards, Maarten
Answer:
Add the following to the audio device in the file: /var/lib/alsa/asound.state
control.2 {
iface MIXER
name 'PCM Playback Switch'
value true
comment {
access 'read write user'
type BOOLEAN
count 1
}
}
control.3 {
iface MIXER
name 'PCM Playback Volume'
value 15
comment {
access 'read write user'
type INTEGER
count 1
range '0 - 64'
dbmin -6400
dbmax 0
dbvalue.0 -4900
}
}
Then run ‘alsactl restore’