just take an RCA cable and cut the end off about 2" from the connector. strip the rubber off, there is some bare wire shielding another rubber covered wire. twist all the bare wire together, strip the little wire inside and twist that to all the bare wire you twisted. solder it preferably, marret it, tape it whatever. the center pin and the outside shield of the RCA connector are now connected(shorted). plug it into the RCA female connector on the amp. if it is not the one on the right on the distortion pair looking down from front to back, stick it in the other one. I find with this amp if you don't have a strong guitar output there is not much distortion. I use a compressor pedal infront with the level maxed to boost the signal. gives me a nice distortion. without it, it's a decent 70's crunch, CCR type stuff on mine.