Amplifier Effects Loops
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. Some guitarists and bassists, particularly new ones, don’t know what an effects loop is, how it works or what to do with it. It’s actually pretty simple, though.
It’s all about signal path. When the signal from your guitar or bass reaches your amp, it goes through a preamp, EQ and power amp—in that order—and is then sent to the speakers, enabling you to blow the house down. Pretty straightforward. But say you want to use outboard effects—stomp boxes and pedals and so forth. Time-based effects like chorus, delay, phasing and flanging, and distortion effects like fuzz, overdrive and, well, distortion. Compression. Other stuff. Where do all those devices go in the signal path?
Honestly, you can put effects wherever you want, but certain kinds of effects definitely sound better when placed at specific points in the signal path. Compression and distortion effects, for example, often sound best between the instrument and the amp; that is, before the signal hits the preamp.
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.
Time-based (or modulation) effects like chorus, delay, phasing and flanging usually sound best when they aren’t colored by the amp’s preamp and EQ circuitry, which is why they work so well in an effects loop. For example, some of these effects—especially flanging and phase shifting—produce an ambient “whooshing” noise that is audibly accentuated by the preamp when these effects are placed between the instrument and the amp. To avoid such unwanted noise, these effects can be placed in the effects loop, where their ambient operational noise isn’t amplified as much because the signal isn’t sent to the outboard effects until after it has already gone through the preamp.
No need, then, to be mystified by the effects loop; it’s just one more helpful feature in your gear arsenal. Use it any way you like, and by all means experiment with effects placement and see what suits you best.