No output from Guitarix with AVLinux with multiple JACK inputs

I recently installed AVLinux for low-latency audio recording, which works very well with my chap USB sound card, provided I line in from an external amp, etc. However, since my bass amp line out is incredibly noisy, I have started looking into using Guitarix with either a USB Rocksmith cable or a 1/4"-3.5mm cable. I have read the AVLinux User Guide (especially re: PulseAudio source/sink), but no matter what I've tried, I don't get any output, even though Guitarix is picking up the guitar (confirmed with the tuner). I'd love to be able to get the Rocksmith cable working as well (same issue - Guitarix can "hear" from the USB but I have no way of hearing any output from Guitarix), but I'd settle for either working. I feel like I have to be missing something quite obvious. I DO get output from other sources (i.e. Firefox, Audacity).