Both channels on, but sound only comes from one?

Flipping the CH 1-2 Select switch to the center turns both channels on at once, and this trips a lot of players up. A common assumption is that this blends both channels from a single input, but that's not how it works. With both channels active, you'll only hear the channel your instrument is plugged into. So if you're plugged into CH 1 with the switch centered, you'll hear CH 1's settings, not a blend of CH 1 and CH 2. If blending tones is your goal, run your instrument into both channels using a splitter or Y cable — the same trick a lot of folks use with the Aviator Cub.