I’ve run at least 2 “monitor only” AllStar Nodes. Although now they are TX capable using iaxrpt, I still use them mainly as monitors.
You don’t need anything more than a Pi and speaker or headphone plugged into the stock headphone jack… no USB sound fob nonsense. Add the following line to your /etc/asterisk/rpt.conf:
outstreamcmd = /bin/sh,-c,/usr/bin/aplay -r 8000 -c 1 -f S16_LE -D hw:0,0,0
I have mine just before the “[functions]” stanza. I suspect this is what repeater systems use to output streaming audio to services like Broadcastify. But the command above just tells asterisk to pipe output to the built-in headphone jack.
Works flawlessly. Mine have only about a half-second or less of latency compared to listening to my local repeater on RF.
Cheers and 73,