24. FAQ (Frequently Asked Questions) with answers!
1.
Saving alsamixer settings
Storing the alsamixer setting can be achieved by performing the following at the command line:
sudo alsactl store
It is possible to save the current state to a file, then reload that state at startup (very useful for the Pi-
Codec boards and use cases)
To save:
sudo alsactl store -f /home/pi/usecase.state
To restore a saved file:
sudo alsactl restore -f /home/pi/usecase.state
2. Using external USB devices
Note that if you want to enable 1.2AMP USB support (to allow USB hard disks to power up when
accessory boards are in use) then you may also want to add the following line to your /boot/config.txt
file:
max_usb_current=1
Please ensure your Pi power supply is able to deliver ~2.5amp if you are powering via mini USB and
enable max_usb_current
3. MPD based audio with volume control
To allow MPD based audio software to control the audio board’s built in HARDWARE volume the file /
etc/mpd.conf may need to be changed to support the correct ALSA mixer name.
This can be achieved by ensuring the'Audio Output' section of /etc/mpd.conf has the 'mixer_control'
line. Below is an example for the Texas Instruments based IQaudIO sound cards (Pi-DAC PRO/Pi-
DAC+/Pi-/Pi-DACZERO)
audio_output {
type
"alsa"
name
"ALSA Device"
mixer_control
"Digital"
}
v32
24-Nov-2019
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