I just spent an hour trying to diagnose why no sound was coming out of my Tube Amp Expander. As it turns out, it was a hardware problem: A defect in the processing unit that controls the notes played on the guitar caused the volume pedal to be rolled all the way back. It’s a glitchy system that is prone to ill-timed &$#%-ups. But in trying to diagnose the issue, I discovered that while my TAE is working just fine, there is actually an error in the block diagram printed on the top of the TAE and in the user manual.
There are two volume control inputs on the GA-FC foot controller, “Pre-Effect” and “Main”. I use the Pre-Effect input which comes earlier in the signal path. The block diagram shows the Input Sig/Peak light coming before both volume control inputs in the signal path. If that were true, then the Input Sig/Peak light should have been lighting up when I played, even with the volume pedal rolled back. But it didn’t. And that threw me off when I was trying to sort out the problem. In reality, the Input Sig/Peak light is after the Pre-Effect volume control input in the signal path, proven by the fact that the light didn’t come on. (However, the Main volume control input is downstream from the light and behaves as expected.)
It’s not a big deal really, but it’s something you should be aware of. Especially when you’re trying to figure out why you’re not getting any sound from your TAE. Imagine: You might send it back to Boss for service and because they’re not likely to have a rolled-back volume pedal plugged into it, they’d send it back saying they couldn’t find a problem with it! Wouldn’t that be fun?