How to specify alternate output device in Alsa config

[John Hyde]

I am using Baresip 1.0.0-4 with a rPi 3B ( Raspbian Bullseye) , that has an onboard 3.5 jack, and also HDMI audio, but I want to use a USB sound card with Baresip. Alsa sees the USB, and can play a test sound thru it, but I cannot figure out how to set this up to send Baresip output to that device only. The card is mono, and I am not sure if there is an issue attempting to output to left+right audio when only the right channel is valid (from speaker-test). Here is all the info from the unit:

root@raspberrypi:/home/pi# aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
sysdefault:CARD=Headphones
    bcm2835 Headphones, bcm2835 Headphones
    Default Audio Device
sysdefault:CARD=Device
    USB Advanced Audio Device, USB Audio
    Default Audio Device
front:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    Front speakers
surround21:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    4.0 Surround output to Front and Rear speakers
surround41:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=Device,DEV=0
    USB Advanced Audio Device, USB Audio
    IEC958 (S/PDIF) Digital Audio Output
sysdefault:CARD=vc4hdmi
    vc4-hdmi, MAI PCM i2s-hifi-0
    Default Audio Device
hdmi:CARD=vc4hdmi,DEV=0
    vc4-hdmi, MAI PCM i2s-hifi-0
    HDMI Audio Output

root@raspberrypi:/home/pi# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones]
  Subdevices: 8/8
  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
  Subdevice #7: subdevice #7
card 1: Device [USB Advanced Audio Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: vc4hdmi [vc4-hdmi], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

root@raspberrypi:/home/pi# cat /proc/asound/modules
 0 snd_bcm2835
 1 snd_usb_audio
 2 vc4

cat /etc/asound.conf
pcm.!default {
type hw
card 1
}
ctl.!default {
type hw
card 1
}