How To Use An Effects Loop: Guide And Diagrams

In the early days of guitar amplification, it was easy to get a great sound from effects right through the front of an amplifier. Most amplifiers in the early days of amplification were clean pedal platform type models without a loop.

Headroom was accomplished and even sought after to get the true tone of an electric guitar. Slowly, as preamps began to provide break up or distortion, things began to change. Effects were slowly becoming “chewed up” by the clipping preamp and their sound took a rather big hit!

Today, you will find one or more effects loops on most amplifiers, but most people do not understand how they work.

Effects Loop

What Is An Effects Loop?

The effects loop is a circuit in an amplifier designed to insert external devices like pedals after the preamp but before the power section. These devices require small signals, and so the effects loop must condition them to work optimally with the amplifier.

This prevents time-based or modulation effects like reverb, delay, or chorus from getting altered in a preamp designed to distort. The distortion from a preamp alters time-based effects so badly in some cases that they do not sound remotely close to the way they were designed to.

This circuit prevents this altering and provides an optimal sound from external devices. This is accomplished by inserting them after the distorting preamp and before the power amplifier.

Pedal Board and Amplifier

Why an Effects Loop Is Important

Most guitar players have these external devices, either in the form of single pedals or multi-effect processors. Some of these effects sound incredible and do an amazing job of providing players with great tone.

But have you ever noticed that when you run delay, reverb, or chorus through your drive or high gain channel on an amp, it doesn’t sound right?

If you run the same effect through your clean channel, it will sound great, just the way it was designed to. What you are hearing is the modified version of the effect through your distortion channel.

Now, some effects are fine through the distorting preamp, but anything time-based or modulation is going to be altered. This is not how to get the optimal sound from these devices, and this is where your effects loop comes to the rescue.

Setting Up an Effects Loop

Setting up your effects loop is generally quite easy. You will see that the loop has a “Send” and a “Return” jack. Sometimes they are also labeled In and Out, or preamp and power amp, depending on the brand. 

You will want to make sure that you are using high-quality cables to connect your effects or processor. We generally recommend assemblies with twisted pair conductors, like the D’Addario Custom Series Twisted Pair Cables.

This will make sure that you will prevent injecting noise into your signal.

Connect the “Send” jack to the input of your effects pedal or processor, and the “Return” to the output. If the amplifier has any send or return level controls, you will want to set these while playing.

One thing to note, is that the send level control should be set after your preamps are adjusted. This will prevent any signal level changes should you need to adjust your amplifier’s channel outputs.

Clipped Sinewave Diagram

When setting your send control, keep in mind that some pedals are very sensitive to signals above instrument level and will generally begin to clip.

The effects of clipping will be loss of treble and a dull, lifeless sound or added distortion. Should this be the case, turn your send level down until everything sounds right.

Once you have this set, any return level controls can be turned up in conjunction with the master to get the desired output volume from your amplifier.

For any other questions about setup, make sure to also take a look at your amplifier’s manual, this will help should you get stuck!

Effect Loop Pedal Diagram

Effects Loop vs Front of Amp

There are some incredible overdrive and high gain channels from today’s amplifiers. The sound and feel can really inspire players. But most players make the mistake of putting all their effects through the front of the amp!

The main difference between using the effects loop vs the front of the amp is that guitar pedals and devices respond differently to either connection method. Time based effects, like delay and chorus, will perform better in the loop. Others, like distortion and overdrive, are better suited to the front of the amp.

You see, a preamp that uses heavy distortion alters your guitar’s signal so much, that it can also change the effects passing through it. 

Not only do the amps drive channels alter the signal by distorting it, there is also a level of filtering. This filtering changes frequencies of your original guitar signal.

This can be disastrous to the sound and performance of effects pedals because it changes them as well! So that great chorus pedal you bought because it sounds so good on the clean channel, hate to say it, but if you are using it through a distorting preamp, it’s not the same anymore.

In the picture below, you can see what the signals look like electrically. On the left is a clean signal, which is normally what you will see coming from an instrument, but far more dynamic.

On the right is a signal that has been clipped or distorted. This is what a distortion or overdrive channel would look like. As you can see, the top and bottom of each wave has been clipped off. This missing part of each wave is essentially lost signal information.

And so if your time based effects go into the over driven channel, you can imagine what might happen to them once the preamp chews them up.

Amp's Effects Loop signals

Different Types OF Effects Loops

Once amp manufacturers began including effects loops on their products, players could then begin running sensitive devices through them.

This allowed the amp to voice the distorted signal and then run that new tone through the effect. This keeps the sound of the effect intact and optimal, just like it was designed to be.

But there are two types of loops and I feel it’s worth exploring them so that you understand how they work. If your amp has one it’s going to be either series or parallel.

The Parallel Effects Loop

Parallel Effects Loop signal path diagram

The parallel effects loop is the less common circuit design, but shows up enough to justify looking at. This particular circuit mixes your amps dry or original signal, with the modified one.

When your effects return to the amplifier, there is normally a control that allows you to mix the wet and dry signals together. This control allows you to have more of one and less of the other. Mixing more of a dry signal with a bit of the wet can really give you a great sound.

The only issue with the parallel effects loop and some devices are phase issues. But this can also turn out to be a great sound depending on what you are running.

Effects like EQ, tremolo, and noise reduction don’t work as well in this type of loop unless set for 100 percent wet, but even then the dry signal can still be problematic.

Now that is not to say the parallel effects loop is a bad idea, it has its place!

But if you are running your devices straight through the front of your amp, then the serial loop might be a better choice for you when getting started with it.

The Series Effects Loop

A Series Effects Loop signal path diagram

With a serial effects loop, your entire signal is being changed by the device you are running it through.

So when you send your signal from your amp to your effect pedal or processor, the preamp is running in series with the connected device.

It is then sent back to the amp from the device as one path from send to return.

The nice thing about a serial loop is that you can essentially run any effect you want in it.

There is no dry signal running in parallel with the device chain, it is 100 percent wet when it comes back to the amp. It is a very versatile circuit design and is really all you will need for an effects loop.

Effects Loop Controls

Many amplifiers have effects loops that do not have any controls associated with it. You simply plug in your pedals or devices and adjust the master volume to taste.

There are other amps that include controls with their loops. These can be terms like

  • Send level control
  • Return level control
  • Foot switchable control
  • MIDI controllable loop

Send Level Control

The amplifier’s send level control allows you to set the outgoing signal to your pedals or processors.

Effect pedals work with instrument level and can not handle a signal any hotter than that without clipping.

But some processors work with line level for optimal performance and some amps allow you to provide both signals with the send control.

When setting up the control, if you have a pedal that is clipping or sounds dull, turn the level down until it is resolved.

Return Level Control

Your return level control simply sets the signal intensity coming back to the amp from your pedals or processors. This control is not seen very much on devices, as the master volume takes care of this for you.

But should you find one, it can assist with getting the right signal back to your amplifier.

Foot Switch Or MIDI

Foot or MIDI controlled effects loops on amplifiers allows you to turn them on or off. This can be very handy if you are using MIDI control and don’t need to turn each effect off manually.

Turning the effects loop on or off can take care of all the devices at the same time and can be a handy feature.

FX Loop Controls and Jacks

Buffered Effects Loop

You may have heard the term “buffered” before, but not understood what it means. This is an important part of signal transfer in circuit design and really needs to be considered.

Effects loop buffering is done by designing a circuit that provides the most optimal conditions to send a strong signal from one device to another. These conditions include the lowest impedance, and strongest signals possible without degradation.

Most amplifiers on the market have buffered loops, but some techs are known to install one and not provide this type of circuitry.

Buffering the signal sent to an effects pedal or processor is normally done by a vacuum tube, op amp or transistor.

Without really getting into the science behind it, if the impedance and signal are not right, the quality of sound can be degraded badly.

Dull treble, weak signal and noise among other things can result.

But by creating a circuit that buffers the signal, you get the best quality sound when it is transferred between your equipment.

Amps With Effects Loops

If you’re looking for an amplifier with an effects loop, here are a few popular models that you should check out!

Which Effects Go In The Loop

Here is a brief look at the effects you will want to run in your loop. The order in which to run them is not something we will look at here, however, but can be found in this article showing you how to use your pedals!

Time Based Effects

  • Delay
  • Reverb
  • Chorus
  • Flanger

Modulation

  • Tremolo
  • Phase

Foundational

  • EQ
  • Noise gate
  • Buffer
  • Volume

Other

Some distortion pedals work better in the loop.

Conclusion

Spend some time learning your effects loop and what works best for your rig. One of the things you might realize is that your sound is just so much better when using the loop.

Most players don’t know how to use it and just run effects into the front of the amp and miss out on its benefits.

Another thing that can benefit you is the 4 cable method.

This technique will allow you to find some amazing control in your rig. It might be just what you have been looking for in finding some incredible tone as well!

Photo of author

Don East

My name is Don East, I'm the editor for Killer Rig. I've been playing guitar for over 20 years and have designed and manufactured products like guitar amps, effects pedals, and more. Over the years I have played in many bands and have a deep love for quality gear.I am an electrical engineer and have a passion for music gear, and now want to share what I know with the community!

5 thoughts on “How To Use An Effects Loop: Guide And Diagrams”

  1. Hey thanks so much for this article! I’m just now digging into the effects loop world. I was wondering… when you run a series effects loop, should I be setting my FX loop chain to 100% wet? (I’ve got reverb and delay only in that loop.) It seems strange to not have a ton of control on the ratio of dry signal to wet signal in this setup. Maybe I should stick a volume pedal and a clean boost in the FX chain to give myself a little more “control” over the amount of wet effects in this FX loop?
    Thanks in advance!! 🙂

    • Hi Sean,
      With a series FX Loop, your signal will normally be 100% wet depending on the configuration of your effects. If you are splitting the signal somewhere in your chain, then perhaps you may have more control over the amount of wet and dry signal being sent back to your amp. But normally a series FX Loop with effects daisy chained together will produce a wet signal being returned to your amp. A parallel loop will offer more control over the wet to dry ratio of your signal.

  2. Looking for some ideas/suggestions/tips on arranging time based FX with respect to their order for FX looping. As I’ve come to understand, its a “Season to Taste” endeavor, but perhaps there are some “Rules of Thumb” as to how a certain order would make a specific affect more pronounced, or not, or better blend if you will depending on where its placed in the chain. Appreciate your articles. Brian Pitman

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