The Ins & Outs Of Effects Loops

If you’ve been a guitarist for more than five minutes, you’re pretty familiar with effects. Effects can morph our plain guitar sound into something from outer space or just make it seem a little bigger than it actually is. There are many different kinds of effects out there, and many theories stating the ‘correct’ order of effects in your Chain of Sonic Domination. One thing everyone can agree on is that eventually, all those effects have to get plugged into an amp. In the old days, when men wore high trousers and suspenders, there was only one way to plug anything in – the singular jack called ‘input’ – and it was good. Amps soon got more sophisticated, and in the back of most modern amps are a pair of jacks which get the title of ‘effects loop.’ For the uninitiated, this article will explain what these jacks are for, and why at least some of your effects should get plugged into them.

I don’t bother with those jacks, they’ll start a fire.

Rectoverb25-LoopWell no, unless you fill them with gas and light them on fire.* These jacks are insert points between the preamp (the main distortion-producing stage in modern amps) and the power amp, which takes that sound and makes it much, much louder. See, some effects sound especially good going before the preamp. These effects, like compressors, overdrives, Seymour Duncan Dirty Deed Distortion Pedal, wahs, and even phasers, should be plugged into the input of the amp. So the signal chain should be: Guitar>These Effects I Just Listed>Amp.

OK, why should I use those jacks, then?

If you use a distorted amp, put this in the loop.
If you use a distorted amp, put this in the loop.

If you get your distorted sound from the amp itself, and you like effects like chorus, flanger and delay, you will most likely get a clearer, cleaner sound by using these mystery jacks on the back of the amp. The idea is that you plug a cable into the effects loop send jack, into the input of, say, a delay pedal like the Seymour Duncan Vapor Trail Analog Delay. You would then plug the output of the delay into the return of the effects loop. The theory behind all this is if you present an echoed sound to the preamp, the sound will be affected by the compression and distortion that the preamp generates. This sounds muddy and indistinct, as the preamp compresses and distorts every echo while trying to compress and distort your original guitar signal as well. By placing the delay pedal after the preamp instead (in the effects loop), it echoes the already-distorted signal, so your individual repeats are clear and they don’t interfere with your playing. Keep in mind, there are a few different types of effects loops, which I will cover in the next sections.

Serial Effects Loops

One of my amps with a serial effects loop.
One of my amps with a serial effects loop.

These are the most common types of loops, and the ones I have shown in the pictures above. These are a hard detour on the road between the preamp and power amp. Normally, the signal passes straight from the preamp to the poweramp, until something is plugged into the effects send jack. This diverts the entire signal down that cable, through a chorus or delay pedal, and back on the road to the power amp via the effects return jack. Here the balance between the dry, unaffected signal, and the wet modulated signal is set on the pedals themselves, usually with the mix knob on the respective pedals. Since all of the signal from the preamp is being sent to the pedals, make sure that the level you get from the pedals is the same as going to the pedals. Check this by having the effects on, and unplug both jacks on the effects loop. If the volume suddenly jumps either up or down, you will need to balance them by using the mix knobs on your pedals.

Parallel Effects Loops

My other amp has a parallel effects loop. Note the mix knob.
My other amp has a parallel effects loop. Note the mix knob.

These are easy to spot, as they usually have a mix knob right next to the effects loop jacks. The idea is that you get to choose how much of the preamp signal gets routed to your effects. Here, when using a delay pedal, you would set the mix to 100% wet, and set the ratio of dry to wet signal with the mix knob on the amp. These amps will preserve more of the ‘amp’ sound, rather than ‘effect’ sound. Since the signal between the preamp and power amp is never broken, you get to mix in as much or as little effect as you want, much like an aux send on a mixer. You can see in the little illustration below how series and parallel loops differ:
Some people don’t want the entire sound of the amp going to their effects, and some people don’t care. It is really up to you to decide how you want to use effects. And remember, the most groundbreaking sounds in music were made by people not following the rules. Just don’t use gas, please.
Do you use the effects loop on your amp? What are your favorite effects to use?
*Don’t do this, as it will start a fire.

Join the Conversation


  1. I use chorus in the input of the amp. I prefer the smoother sound of chorus > distortion than the other way around. Delay and harmonizer go in the loop. Oh, and flanger sucks.

  2. Because the nerve center of my pedal board is a Boss GT-8, I don’t even use the preamp if I can avoid it, my rig sounds best running into the effect return of a tube amp, save for perhaps a JC-120, it may be solid state, but you can’t compete with that built in stereo chorus placed conveniently past the effect loop…

    1. Hey I’m not sure the gt8 can do this, but Google “the four cable method” … with some floor based effects processors, you can use this method to set some effects before the input AND other effects in the effects loop.

      1. It totally can, but the preamp in my main show pony isn’t quite my taste, so I have tailored the GT-8’s built in preamps to suit each tone I desire, and because I only require an effect return, any decent tube-driven backline will carry my tone if I can get to the effect return(s), this also lets me implement the GT-8’s stereo capabilities with multiple amps or stereo amps

  3. I use mine for EQ, Delay, Sonic Stomp, and any modulation effects. For sure, the delay sounds so much better post pre-amp.

  4. I agree, flanger sounds better in front. I usually get an EQ, tremolo and a delay in the fx loop and works for me.

  5. Even though you said that the preamp generates the distortion effect , can you still run another distortion pedal through the fx loop to give a beefier sound or is that just to much

    1. Ummm, I’d say don’t do this. Distortion in front, time based stuff (only) in the loop of a distorted amp. I use time based stuff in front, but my amp is pretty clean.

  6. What would be better for a BBE sonic maximizer? Effects loop or tied into the end of the pedal train?

    1. I have one and I put it very last in the effects chain in the effects loop. I think of it as a post e.q. it’s the secret weapon at the end right before the signal hits the power section.

        1. Hmm that does make sense. I don’t modulation effects but it would make sense not to add post eq to them.

  7. My chain is kind of complicated cuz I’m using two effects units a roland GP-8 along with a boss GT-PRO I have a voodo blue crate amp very popular in the eighties, the things is I’m using both loops jacks on both units but also using the 4 cable connection and for the last of this chain an alesis miniverb 4 as a reverb, at first I was using the distortion of the amp combined with the different distortion of the racks units, it was good but as a musician we’re always looking for more now im trying a new conection without using the distortion of the amp that’s why I’m looking forward to buy a marshall jcm 800 with one channel and u know looking for the right sound for me..

  8. I run a Randall 300 watt Cyclone amp clean and I use a boss rackmount preamp with all my effects would it be better for me to use the effects loop or not

    1. That depends 100% on what effects you’re using and how you like to use them. Typically, filter effects (overdrive, distortion, wah, etc.) sound better in front of the amp and time-based effects (reverb, delay) sound better in the loop. Modulation effects can be placed either in front or in the loop for different results. Many people prefer the sound of a phaser in front, but like chorus and tremolo in the loop. It’s really up to you.

  9. Is it safe to run a second preamp through the effects loop? A Hartke Bass Attack preamp in particular, like this:
    Bass —-> Amp input —> FX Send —-> Hartke Bass Attack preamp —> FX Return
    It makes the amp sound a lot louder, like a booster, but is it safe, or can it damage the power amp?

  10. I’ve got a question… I have a Peavey Rockmaster preamp. It has SEVERAL loops. I usually do this… Rockmaster – rack effect in loop – then output of the RM into a power amp. However, since the RM is a line-level (-10) unit, why can’t I run it like this.. RM >> Effect >> power amp? What are the pros/cons to this?

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