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How to Use a Guitar Amplifier’s Effects Loop

Peavey Amp Effects Loop

What is an Effects Loop?

You may have noticed two jacks on the back of your guitar amp labeled “Send” and “Return” before.  Some brands may also label them “Pre-Amp Out” and “Power-Amp In”, or something similar, but it’s the same set-up, with different names.  The Send/Out is the jack where the signal leaves your amp before traveling through your effects pedals and the Return/In is where you route the signal back to your amp.  You’ll be using your existing patch cables and pedals, but placing them in a different position in your signal chain.

An effects loop allows you to alter your signal after it’s been through the amp’s preamp stage, but before it is sent to the power-amp stage.  As a refresher, the preamp stage is the first portion of your guitar amp that your guitar’s signal encounters and it increases your signal, also known as adding gain, and can add color to your tone.  The power-amp stage is the final step in your guitar amp’s wiring and only adds volume.


Effects loops come in two types:

  • Series Loops – In a series loop, your entire signal leaves your amp and travels through whatever pedals you have in your effects loop. There is a chance that the pedals in your loop may somewhat color your tone, even when not engaged.  This will vary by pedal and many today have reliable true-bypass.  Series loops can also run in to trouble with some digital effects processors, like a digital delay, due to issues created in the analog-digital-analog conversion.

Series Loop

  • Parallel Loops – In a parallel loop, only a portion of your signal travels through the effects loop and the remainder travels directly from your amp’s preamp to the next stage in the amplifier. Amplifiers with a parallel loop have a knob which allows you to control how much of your signal is sent through the loop.  In many amps, this mix knob can be set so that 100% of the signal flows through the effects loop, effectively making it a series loop.

Parallel Loop

It’s also possible to test your amp’s effects loop to see whether it truly is a series or parallel loop, as advertised.  For a series loop, plug a patch cable from the Send output jack in to the input of one of your pedals, but don’t connect the other side back to the amp.  If it really is a series loop, there should be no sound output from your amp when you strum your guitar.  For a parallel loop, if you set your mix knob to 100% wet (all your signal going through the loop) and run the same test, you should also not hear any sound, if it’s a true parallel loop.


When to Use an Effects Loop?

In general, you want to use an effects loop to avoid the possibility of the preamp stage of your amplifier muddying your sound.  As we discussed in a previous article about guitar signal chains, the most often used sequence for effects pedals is:  gain – modulation – delay.  The theory is that you want to apply gain first to your signal and then modulate or delay that signal afterwards.  However, if you are also utilizing the gain in the preamp stage of your amplifier, it is possible that your sound will be adversely affected if you are applying a modulator or delay before the signal reaches the preamp.  To solve this problem, you can utilize your effects loop which means all the gain boosting, including the preamp stage of your amplifier, will occur before it reaches your modulation and delay pedals.

Henretta Engineering Moody Blue Reverb Guitar Effect Pedal

Henretta Engineering Moody Blue Reverb

Helpful Tips:

  • If you are running the preamp section of your amplifier “clean” or with no gain added, utilizing the effects loop probably won’t make much difference.
  • With a gain-type pedal (compression, fuzz, distortion…) you’ll nearly always want to put it before your amp, in the signal chain.
  • For a delay-type pedal (reverb, echo, delay…), you’ll usually want to place those in your effects loop.
  • Modulation pedals (chorus, tremolo, phasers & flangers) are often a mixed bag. If the effect is intended to color your tone, as opposed to just repeating it like a delay or reverb, you probably want to place it in front of your amplifier in the signal chain.  You may have to do some experimentation to see if certain pedals work best before the amp or in the loop.
  • If you use a volume pedal, experiment with placing it before your amp or in the loop, and see which works best. Placing the volume pedal before your amplifier can affect or reduce the gain/distortion created by the preamp section of your amplifier.  However, placing your volume pedal in the effects loop generally only affects the end volume of your sound and can be used to highlight sections in a song, like a solo section.
  • Booster pedals work similarly to volume pedals. Placing them in your chain before your amplifier can affect the distortion of your tone, while placing them in the loop just allows you to affect your volume.
  • If you using an EQ pedal, placing it before you amplifier can also have a different result than placing it in the loop. A lot of guitarists like to put the EQ right after their guitar so that they can adjust the guitar’s general tone or first thing in the effects loop so they can adjust the amp’s tone.
  • You should also check your pedal’s instruction manual to see if the manufacturer offers a recommendation of where the pedal works best.
  • If effects in your loop are creating feedback or unwanted noise, check if your amp has an output level control for the loop and dial it back a little. If this doesn’t help or your amp doesn’t come with a level control, you can try adjusting the amp’s blend/mix on parallel loops.  Another option is to experiment with the settings on your effects pedals too.  Some pedals allow you to adjust the output level and this may help.

When working with your signal chain, experimentation really is the best option to find your ideal tone.  You can switch up the order of your effects pedals.  You can move pedals in and out of the loop.  You can also adjust the settings of you pedals and amp.  The options are limitless.  Once you find something you like, be sure to note what changes you made, so you can easily replicate them, in the future.

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