Set volume DAC on Pogoplug Pro

[treble]

I have a Pogoplug Pro. I am trying to get the sound working with my 'Logitech USB Headset' external dac. However, alsamixer or amixer doesn't like it. Are there other ways to set the volume? I am also trying to run squeezelite on it, but get some alsa-errors, in addition to no sound... See session below. Any ideas what I can do other than giving up and get an E02?

$this->bbcode_second_pass_code('', '[root@alarm ~]# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Headset [Logitech USB Headset], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
[root@alarm ~]# alsamixer
cannot load mixer controls: Invalid argument
[root@alarm ~]# squeezelite
[21:18:26.688420] alsa_open:349 unable to set hw params: Input/output error
[21:18:36.698361] alsa_open:349 unable to set hw params: Input/output error
[21:18:46.708356] alsa_open:349 unable to set hw params: Input/output error')