Here’s a quick tip or two about creative uses for effects loops. I discovered this first one with the “evil” Fender Twin amp with the red knobs, but it sometimes works on other amps too.

For the first forty years or so of the electric guitar, you plugged your guitar straight into the amp. In the sixties, effects in pedals became widely available, but the signal path didn’t change. You simply inserted your guitar cable into the effect input and then plugged the output into the amp. This was fine until people started trying to use higher quality rack mounted effects originally designed for recording studios in their setups in addition to their cute little pedals. These rack units were designed for pro audio usage (which has different design conventions than guitar amps do) and the level mismatches in the signal chain played havoc with your tone when you patched them in front of the guitar amp, like you would with a fuzz box. The tiny output of an electric guitar simply wouldn’t register without turning the input up all the way and generating all sorts of unpleasant noise.

What to do?  There are a few old amps that have effects loops without any controls, just input and output jacks. (My Mesa/Boogie Mark II-A, made in 1978, has one, as do some Peaveys.) But the vast majority of amps available, new or used, that have effects loops offer independent controls for input and output levels.

An effects loop with any kind of input and output level controls is actually a gain stage in the amp. It is designed so that you can optimize the signals going to and from any conceivable effects device  so that it works effectively with an electric guitar and amp.

Most people who just play straight into the amp, or through a couple of pedals, don’t use the effects loop. But even if you don’t patch your effects into it, an effects loop can be useful.

So…if you want to play with this gain stage, just plug a regular 1/4″ guitar cable into the input and output jacks.  Usually a 3″ cable is long enough; the shorter the better.

Voila! You are now inside the amp! Now you can crank the input on the effects loop, lower the output, or both, depending on what you want.  (Turn both the input and output knobs down fairly low and have the amp volume low as well before you start experimenting. If you don’t, you could really surprise yourself. Bring the input of the effects loop up gradually, then the output.)

Theoretically, you could even patch a regular on/off switch in between the input and output of the effects loop and get an extra channel out of the amp. In some cases, depending on the amp and the kind of switch you use, the click of the switch may be annoying; this is why I say “theoretically.” Try at low volume first!! Loud clicks can hurt your ears and your speakers, though they probably won’t damage the amp itself.

You can also use the effects loop as an extra line out, either to a direct box, another amp, or a tuner. Start with the output level control at 0 though. Play and bring it up gradually until you have enough level to do what you want. You can patch additional effects in line with the output to the other amp or DI if you like. More buttons to press!