Raspberry Pi Zero W にUSBスピーカーを接続する

# uname -a
Linux raspberrypi 4.14.98+ #1200 Tue Feb 12 20:11:02 GMT 2019 armv6l GNU/Linux

.asoundrcを新規作成

# cat ~/.asoundrc
pcm.!default {
    type plug
    slave.pcm "dmixer"
}

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

pcm.dmixer {
    ipc_key 1024
    type dmix
    slave {
        pcm "hw:1,0"
    }
}

現在の状況確認

# cat /proc/asound/modules
 0 snd_bcm2835
 1 snd_usb_audio

# cat /proc/asound/cards
 0 [ALSA           ]: bcm2835 - bcm2835 ALSA
                      bcm2835 ALSA
 1 [MicroII        ]: USB-Audio - Audio Advantage MicroII
                      C-Media INC. Audio Advantage MicroII at usb-20980000.usb-1, full speed

# raspi-config

[7 Advanced Option] > [A4 Audio] > [1 Force 3.5mm ('headphone') jack] 

rebootして音声テストを実施

# aplay /usr/share/sounds/alsa/Front_Center.wav

参考
Raspberry Pi 3にUSBスピーカーをつなぐ
https://umiushizn.blogspot.com/2017/10/raspberry-pi-3usb.html