I'm guessing that's your effects loop. You can run pedals and other fun toys through there so they come into the signal chain after the preamp.
Recognized by the Official EG/GG&A Who To Listen To List 2008
Quote by utsapp89
^I'd let a pro look at it. Once you get into the technicalities of screws...well, it's just a place you don't want to be, friend.
whats the brand and model of your amp?
MIM Fender Telecaster
SX GG1 Junior (Les Paul Special clone)
Dillion Canada DXC 58 (DC Les Paul Junior)
Fender Joe Strummer Telecaster
Squier CV Duo Sonic
Epiphone Les Paul Junior Special
Squier Jazz Bass
Vox DA 15
Fender FM 212R
Quote by Redsx158
There are 4 jacks on my amp one says input above it and another says footswitch above it. Those 2 I can figure out. What about the jacks which say Power In and Pre Out above them.

If you plug something into "power in" it will bypass the inbuilt pre-amp and go straight to the power amp.

If you plug something into "pre out" it will bypass the inbuilt poweramp.

Or that's what I'm guessing because of their names.
Preout is simply another name for fx send and power in is another name for fx return. I have an amp that says line in and line out but is just the fx loop.
it's for the fx loop

Quote by lrc95

hi, i was just wondering how to post a thread?

Quote by AS I LAY DYING!
and USD is equal to how much in US dollars?

Quote by Armchair Bronco
Everyone must own a DS-1 at some point in their playing career.