Effects loop on the back of a Fender Band-Master® VM head (above), and effects loop with level controls on the back of a Fender TB-600 bass head (below).
Many guitar and bass amps have a feature called an effects loop. Time-based effects like chorus, delay, phasing and flanging, and distortion effects like fuzz, overdrive and, well, distortion. Compression. Some effects, however, like the time-based effects mentioned above, tend to sound cleaner and more pronounced when the signal from the instrument hits your amp’s preamp and EQ section first and then hits your effects. That is, these effects sound better when they’re placed between your amp’s preamp and power amp stages. Therein lies the beauty of the effects loop.
A typical effect loop lets you do just that—place outboard effects into the signal path between the preamp and the power amp. The effects loop is usually found on the back of the amp and consists of two jacks, “effects send” and “effects return” (some even have their own level controls). When the loop is in use, the signal is rerouted to your effects pedals via the effects send after it has already hit the preamp and EQ stages; the signal is brought back to your amp via the effects return before it hits the power amp.
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