I have a setup in which I have been using the DAC on a Pi3 quite happily using alsa with DMIX configured via the /etc/asound.conf file. The application is currently using two instances of MPLAYER to play simultaneously - one a silent file and one the real music - the silence is there to reduce the "click" at the start and end of playback hence the use of DMIX. Otherwise this would be a single player instance application.
I swapped the DAC for the AMP and set the /boot/config.txt file to use the AMP settings but there is an issue. With the DAC, I get an output amixer control called "Digital" and I had been using that to adjust the overall volume. But with the AMP installed, I only get Master and Channels. Using MPLAYER to play a file I get an error
[AO_ALSA] alsa-lib: pcm_dmix.c:989:(snd_pcm_dmix_open) unable to create IPC semaphore
I confess to having got the system to work with lots of googling and copy/paste etc. So I'm not really sure how I have it working for the DAC and hence do not know what I should address to make it work for the AMP. Any suggestions toward a solution would be much appreciated.
My DAC working asound.conf is:
type hw card 0
Thanks in advance