maybe, the Rpi version synthv1 v0.8.6 is dang old (~3yo)...
however, your PC version is pretty recent and it should work as is. (though v0.9.15 is the most recent, but nevermind)
have you double-check on your JACK settings, either on Cadence or QjackCtl, whatever you use to run the JACK-server? how about first making sure JACK is up and running and playing audio right, then launch synthv1_jack and then, only afterwards, connect those ins and outs?
make sure your audio interface or soundcard, USB external or internal whatever, is the one you're after (ie. connected to the speakers :))
maybe, the Rpi version synthv1 v0.8.6 is dang old (~3yo)...
however, your PC version is pretty recent and it should work as is. (though v0.9.15 is the most recent, but nevermind)
have you double-check on your JACK settings, either on Cadence or QjackCtl, whatever you use to run the JACK-server? how about first making sure JACK is up and running and playing audio right, then launch synthv1_jack and then, only afterwards, connect those ins and outs?
make sure your audio interface or soundcard, USB external or internal whatever, is the one you're after (ie. connected to the speakers :))
seeya