I'm supposing this is a 1D10T error on my part. First off, it works; I just am confused as to why it works. So I'm running sound, recording and performing at a gathering of about 200 people in some rich person's living room in a couple weeks. I was testing out some new gear in preparation and ran into this issue. I wanted to send 4 vocal mics (XLR), an acoustic guitar and a ukelele (both 1/4") going into a TASCAM US-1800 usb interface to a Harbinger HA120 PA system using a MacBook Pro with GarageBand. I double-checked the TASCAM manual and it shows to use the monitor outs (obviously) for this: And the manual also says that you can manage the balance & levels with the MIX & MONITOR knobs: When I did this, I could see the signal coming into the interface just fine (on each track) but nothing was coming out of the PA speakers despite mass tweaking of all the knobs. After smashing things and flipping over tables enraged, I thought I'd try using the "Line-outs" instead of the "Monitor-outs". And *poof* Suddenly sound came out of the PA! Why? Why is this happening? Just why?