USB Sound Card for Raspberry Pi 3B+ with Ubuntu Mate 18.04.2

I have bought and configured an external USB sound card for my Raspberry Pi.

After plugging in the sound card, here are what I have. Important lines are highlighted.

$ lsusb
Bus 001 Device 004: ID 1941:8021 Dream Link WH1080 Weather Station / USB Missile Launcher
Bus 001 Device 006: ID 8086:0808 Intel Corp. 
Bus 001 Device 005: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 007: ID 0424:7800 Standard Microsystems Corp. 
Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$ sudo aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 7/7
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

After disabling the onboard audio with:

$ sudo vi /boot/config.txt
...
dtparam=audio=off
...

I have these now.

$ cat /proc/asound/modules 
 1 snd_usb_audio
$ cat /proc/asound/cards
 1 [Device         ]: USB-Audio - USB PnP Sound Device
                      C-Media Electronics Inc. USB PnP Sound Device at usb-3f980000.usb-1.1.3.4, full
$ sudo amixer -c 1
Simple mixer control 'Speaker',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 151
  Mono:
  Front Left: Playback 44 [29%] [-20.13dB] [on]
  Front Right: Playback 44 [29%] [-20.13dB] [on]
Simple mixer control 'Mic',0
  Capabilities: pvolume pvolume-joined cvolume cvolume-joined pswitch pswitch-joined cswitch cswitch-joined
  Playback channels: Mono
  Capture channels: Mono
  Limits: Playback 0 - 127 Capture 0 - 16
  Mono: Playback 0 [0%] [0.00dB] [off] Capture 0 [0%] [0.00dB] [on]
Simple mixer control 'Auto Gain Control',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]

Need to set the volume properly (to maximum).

$ sudo amixer scontrols
amixer: Mixer attach default error: No such file or directory
$ sudo amixer -c 1 scontrols
Simple mixer control 'Speaker',0
Simple mixer control 'Mic',0
Simple mixer control 'Auto Gain Control',0
$ sudo amixer -c 1 sset 'Speaker' 100%
Simple mixer control 'Speaker',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 151
  Mono:
  Front Left: Playback 151 [100%] [-0.06dB] [on]
  Front Right: Playback 151 [100%] [-0.06dB] [on]

MPD works properly now!

References:

• https://raspberrypi.stackexchange.com/a/80075