Setup Hifiberry Amp2

To setup the Hifiberry Amp2 you'll have to start by removing the driver for the onboard sound.

$ sudo nano /boot/config.txt

Remove the line dtparam=audio=on

and add the line dtoverlay=hifiberry-dacplus

The final part of the file will look something like this:

# Uncomment some or all of these to enable the optional hardware interfaces
# dtparam=i2c_arm=on
# dtparam=i2s=on
# dtparam=spi=on # Uncomment this to enable the lirc-rpi module
# dtoverlay=lirc-rpi # Additional overlays and parameters are documented boot overlays README
# Enable audio (loads snd_bcm2835)
dtoverlay=hifiberry-dacplus
gpu_mem=256
start_x=1

Configure ALSA

According to the Hifiberry site this part should be optional, but I couldn't get my amp2 to work without it.

Create the file /etc/asound.conf

$ sudo nano /etc/asound.conf

with following content:

pcm.!default {
    type hw card 0
}
ctl.!default {
    type hw card 0
}

Make sure you have no .asound.conf file with different settings in your home directory, if there is delete it (or rename it)

Reboot to start with the new settings and check if the device is listed by typing aplay -l:

 $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_dacplus], device 0: HiFiBerry DAC+ HiFi pcm512x-hifi-0 []
  Subdevices: 0/1
  Subdevice #0: subdevice #0

Set volume

Before testing it is advised to lower the output volume. By default the amp will output at 100% which might damage your speakers.

Check current volume settings:

$ amixer sget Digital
Simple mixer control 'Digital',0
  Capabilities: pvolume pswitch
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 207
  Mono:
  Front Left: Playback 179 [86%] [-14.00dB] [on]
  Front Right: Playback 179 [86%] [-14.00dB] [on]

Set volume to 60%:

$ amixer sset Digital 60%

Test playback

To test playback it is recommended to install mplayer because it can play all types of files

$ sudo apt-get install mplayer

To start playback a testfile type:

$ mplayer http://www.waailap.nl/upload/test.mp3 (CTRL+C to abort playing)

See original article at Hifiberry forum: https://support.hifiberry.com/hc/en-us/articles/205377651-Configuring-Linux-4-x-or-higher