Output RCA volume control

[flatmax]

Hi there,

You can control the volume of the headphone jack and input RCA connectors by default using the commandline tools alsamixer or amixer. However if you want to control the RCA line output volume, you would have noticed that you need to use the potentiometers. If however you want to control it from the command line, then this post explains how to setup the softvol plugin to allow you to control the RCA output connector volume from the command line.

The only audio channel which you can't control in the audio chip of this device is the output RCA connectors. If you look at the wm8731 datasheet you can confirm that Wolfson Micro haven't got a volume control in hardware for that audio channel. For that reason we can use ALSA's softvol plugin to control the volume from the command line or alsamixer, as well as the potentiometer.

Reading the information on softvol here, we need to setup out asoundrc file. After setting up (see the file listing below) we can play music to this new device like so :

Code: Select all

aplay -DRCAVolume awesome.track.wav

We can then control the volume using the master control either with amixer, like so :

Code: Select all

amixer set Master 60%

Or we can control the volume using alsamixer.

If you want this type of volume as the default playback device (so that you don't have to use -DRCAVolume as the audio device) it is explained how to do it here : here

For example, save the following as ~/.asoundrc :

Code: Select all

pcm.!default {
        type hw
        card 0
}

ctl.!default {
        type hw
        card 0
}

pcm.RCAVolume {
    type            softvol
    slave.pcm       "default"
    control.name    "Master"
    control.card    0
}

You can now play any track to it using the ALSA device "RCAVolume".

Hope you are enjoying the use of this product.
Matt

[Johnatansef]

I just got the HD 10 - but can't control the volume. It's so low I can barely hear anything. There doesn't seem to be any directions or way to raise the volume. Any suggestions?

[flatmax]

Hi there,
What is an "HD 10" ?

thanks
Matt

[DokG]

Thanks for the tip. That configuration didn't have any affect for me, but I was able to get it to work using the below content for .asoundrc. I have to control the volume using Softmaster instead of Master (e.g. amixer set Softmaster 50%). According to the softvol plugin docs, you cannot redefine a non-user defined control, which is what I presume Master is (see https://alsa.opensrc.org/Softvol). I assume that's partly why the original configuration caused no change in behavior. To get the default to work right, you have to route it through the RCAVolume device, so then the slave.pcm setting could no longer be "default" because that would cause a loop.

This is my first time reading any of the Alsa documentation or trying to do something like this, so I'm not sure the below is 100% correct but it seems to work for me with my specific hardware/software configuration.

--

pcm.!default {
type plug
slave.pcm "RCAVolume"
}

pcm.RCAVolume {
type softvol
slave.pcm "hw:0,0"
control.name "Softmaster"
control.card 0
}