Ok, I'm a dumbass. I'll admit that from the start. But in the owner's manual for this unit there is no description or coverage of the front panel button which reads "active" and engages a light. I thought it referred to "active/passive" guitar pups like some other amp manufacturers. Nope, it is a bypass control for the entire preamp. When "active" the preamp affects the input, when "not active", it bypasses the preamp and the signal runs from your guitar directly to the power amp. After changing my HO from active to passive pups and in the heat of the moment during a late soundcheck Saturday night, this dumbass couldn't figure that out by myself. I called Sansamp and they are aware of its omission in the owner's manual, but someone higher up in the company doesn't think that function should be described in the owner's manual. Hope this tidbid helps out someone else.