Sendspin on Pi doesnt allow fixed usb hardware name, relies on USB number

[paulcad44]

I have a soundblade installed via usb to Pi P400, its currently usb device 3.

I have the following configuration in /etc/asound.conf as the soundblade only accepts 48khz:

pcm.upsampler {
    type plug
    slave.pcm "softvol"
    # The 'plug' plugin is the only one that understands the 'rate' field
    slave.rate 48000
}

pcm.softvol {
    type softvol
    slave {
        pcm "hw:3,0"
    }
    control {
        name "Master"
        card 3
    }
}

pcm.!default {
    type copy
    slave.pcm "upsampler"
}

In sudo systemctl edit sendspin.service

[Service]
User=sendspin
Group=audio

ExecStart=
ExecStart=/home/sendspin/.local/bin/sendspin daemon --audio-device=upsampler
Restart=on-failure
RestartSec=5

# No ExecStartPost - no timeout issues
ExecStopPost=/usr/bin/pkill -u sendspin sendspin

While this works, its not robust enough to survive a new USB device inserted, using the name of the device in aplay -l , causes an error and the service doesnt load.

Aplay -l ouput:

card 3: SOUNDBLADE [BLUEANT SOUNDBLADE], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0