Compression Pedals: The Ultimate Guide


If you’re new to electric guitar effects pedals, then compression pedals may seem a bit confusing. You’ve probably heard of overdrive, distortion, reverb, delay etc., and know what they sound like. But what’s the point of a compression pedal? 

In this post I’ll go through everything you need to know about compressor pedals, how they work, what they sound like, and loads more to answer all your questions. So let’s get started!

What is a Compression Pedal?

Compression pedals have been around for ages, and they’re used by loads of professional guitarists. They’re not as glorified as distortion, overdrive, delay etc., in fact, I basically ignored them when I first started looking into purchasing my first pedals. But if you’ve ever tried a compression pedal, you’ll understand that they’re one of the most useful pedal effects you can get.

Unlike the main pedal effects you’ve probably heard of, compression pedals aren’t necessarily classed as a sound effect. At least not in the same way something like a wah pedal would be. Instead, they adjust the signal of your guitar. 

Compression pedals are best known for smoothing out the sound of your guitar to make it more even. 

Even most of the best guitarists will agree that they’re not perfect. When you’re plucking the guitar strings, you can’t always pick them with consistent pressure. So some notes sound louder than others. 

Compressor pedals even out the sound by decreasing the volume of strings that are plucked more aggressively. This creates a smoother and more professional sound. It doesn’t work miracles, but it does definitely help your playing sound better. 

what does it sound like?

Compression pedals are best known for their ability to create a smoother and more even sound. So they are able to prevent notes that are plucked lightly from getting lost, and also notes that are played to heavily from sounding harsh. 

They are also capable of increasing the amount of sustain you get from your guitar, because the notes ring out for louder. 

How does it work?

So you already know that compressors have an effect of increasing the volume of strings plucked lightly, and decreasing the volume of strings plucked too heavily, but how does it actually do this? 

A common misconception is that compressors increase the volume of some notes and decrease the volume of others, but this is not technically true. Before we jump into this properly, you need to know about the terms threshold and ratio.

  • Threshold: this is the point a which the compressor will affect the signal. If the signal is louder than the threshold, it will be reduced. But if it is quieter, then it won’t be affected.
  • Ratio: this refers to how much the compressor will act, when the threshold is reached. For example, you can have a 3:1 ratio. This means if the signal is 3dB above the threshold, then the compression pedal will allow the volume to be 1dB. Hence, it reduces the signal by 2dB.
Compressors work by reducing the volume of notes played louder than the threshold. Hence, the idea that they both increase the volume of quiet notes, and the decrease the volume of loud notes isn’t really true. Compressor pedals only decrease the volume of loud notes. 
compression pedal

types of compressor pedals

Compressor pedals are already pretty technical, but to confuse things further, there are also several types of compressor pedals that all act slightly differently. Here’s a quick rundown. 

  • Voltage Controlled Amplifier (VCA): these are the most commonly used and the most versatile. 
  • Optical Compressor: these use a light source to reduce the signal and smooth out the sound. It sounds very natural and soft. 
  • Field Effect Transistor (FET): these act like vacuum tubes (similar to a tube amp) to compress the signal. It sounds less natural than optical compression and acts very quickly.

Compression Pedal Controls

To be able to get the most out of a compression pedal, you need to know more about the controls and how they affect the sound produced. Here are some of the most common controls you’ll find on a compressor. 

Threshold or Level

This refers to the volume at which the compressor pedal will start to work. Compressor pedals work by reducing the volume when the signal is over the threshold, this reduces the volume difference between notes that are plucked lightly or heavily, hence, smoothing out the sound.

If you just want to compress really harsh jumps in volume caused by dramatic picking inconsistency, then you want the threshold to be high (or the level to be low). But if you want to compress pretty much everything, then you’ll want the threshold to be low (or the level to be high). This is commonly seen with country music. 

Ratio or Limiter

This is related to the threshold in some ways. The ratio works by affecting how much the volume is decrease by the compressor. For example, you can have a 5:1 ratio. This means if the signal is 5dB above the threshold, then the compression pedal will allow the volume to be 1dB. Hence, it reduces the signal by 4dB. The higher the ratio, the more the volume is decreased. 

Attack and release

This refers to how long you want the note to be heard, before the compression picks in. The higher the attack, the faster the compression will happen. Fast attack, will sound less natural than slower attack and will cause the most dramatic change in the sound.

Release refers to how long the note is compressed for. Hence, it’s kind of the opposite side of the attack control. 

Blend

This is a control used on a lot of more modern compressor pedals. It allows you to adjust how much of the compressed and uncompressed sound you hear. Blending the sound will allow it to be more natural and seamless.

sustain

This refers to how long the note rings out for. More sustain, means the note will be heard for longer. High sustain is great if you’re using a lot of gain for example when playing metal. 

Tone

Some compression pedals also come with a tone control. This allows you to either brighten or darken the sound of your guitar. If you set it to neutral, the tone control will be bypassed, which is helpful if you’re already using an EQ pedal, or are happy with your current tone settings. 

When to Use a Compressor Pedal

Another thing to consider when discussing compressor pedals, is when to use them. There are two ways of using a compression pedal. You can either have it on all the time, or use it as an extra effect. 

On all the time

If you’re using a compressor pedal to simply reduce the impact of inconsistent picking, or to give you a bit of a sustain boost constantly, then you can just keep it on all the time. If you’re using it constantly, it’s best to adjust the settings to give you a more natural sound. So you can have the attack fairly slow, the release a bit higher, and the threshold fairly low. 

This means that the compression pedal will only kick in and have a more noticeable effect when you accidentally pluck a string way too hard. 

As an effect

Compressor pedals aren’t normally described as effects pedals, or at least in the same way something like a reverb pedal would be. However, you can choose to only activate your compressor pedal some of the time. There are a couple of main reasons why you may choose to do this.

  • For solos: compressor pedals are great at increasing sustain, as well as reducing the impact of inconsistent picking. Hence, they can be turned on for solos or lead sections of a song to give you a thicker and more professional sounding tone. 
  • When finger picking: if there are sections of a performance that require more delicate finger picking or strumming, then you can turn the compression pedal on for these. It’ll again give you a smoother and more professional sound. 

Where does a Compressor go in the Chain?

If you’re using a compression pedal in addition to other pedals, then you need to think about the best placement to get the most out of it. The general rule of pedal placement applies with compression pedals, like it does with most other pedal types: the later it is in the chain (closer to the amp), the bigger the effect will be.

If you place your compression pedal at the very start of your chain, then only the sound of your guitar will be affected, and not the rest of your pedals. So if you’re just using it to even out accidental heavy picking, then it’s a great place to put it. 

However, if you place your compression pedal later in the chain, then it will affect your other pedals. Some guitarists like putting a compression pedal after something that adds gain like fuzz, overdrive or distortion. This generally reduces the effect of your gain pedal. 

One thing I would say to avoid, is putting a compression pedal after any time-related effects like delay or reverb as this often sound quite messy, or just eliminates the effect of the pedals. Think about it, if you compress a delay pedal, then you will be compressing all the repeats of the notes as well. 

In my opinion, it’s best to put a compression pedal early on in the chain, before any other effects like wah, gain, modulation, pitch shifters or time-related effects. This way, your compression pedal affects the signal of your actual playing, rather than the other effects. But try out some other positions and see what sounds best to you!

pedal chain order

Do I Need a Compression Pedal?

One of the most common questions guitarists ask about compression pedals, is whether or not they actually need one. Like all pedal effects, you don’t actually need them to be able to play your electric guitar. But do they have their advantages. Of course they do! 

You should think about purchasing a compression pedal if any of these points relate to you.

  • You want to increase your sustain
  • You’re looking for a smoother tone 
  • You want more control over your sound than your amp gives you
Although you don’t necessarily need a compression pedal to make your guitar sound great, they are in my opinion, one of the most important effects pedals out there. They’re not as glamourous or as well-known as distortion, overdrive, delay, wah, reverb, the list goes on and on. But, they can have a huge impact on your sound. 

They’re not like a typical effect, instead they’ll give you an overall better tone by improving the sustain, and also by making it sound smoother and more professional. That’s why a compression pedal was the second pedal I ever purchased (after a Boss OS-2), because I was looking for a way to improve my overall tone, rather than add any extra effects. 

Is Too Much Compression Bad?

So you’ve probably guessed it by now, I am a pretty big fan of compression pedals. But are there any downsides to them? I’ll put my love of compression pedals aside for a moment, and discuss this topic. 

It can sound unnatural  

If you use a lot of compression and have the level high, the threshold low, the attack fast, and the release slow, then you’ll get a very unnatural sound. Now, this can appeal to a lot of guitarists, however, some really hate this artificial tone it creates. 

This isn’t really a drawback of compression pedals though, more just how you use them. You can still get a natural compressed sound, that evens out any harsh volume changes caused by heavy picking. There are also situations where you want a really compressed tone, for example when playing quick country finger picking. 

it can cause sloppy picking

Now again, this isn’t really a disadvantage of compression pedals themselves, but of how they can be used and abused. So you know that compressors are great for smoothing out the sound of inconsistent picking, which is really helpful. However, you can get reliant on them. 

If you use really heavy compression often, it can cause you to become a bit sloppy when you’re playing, because the pedal will compensate for it, which isn’t really the idea. It should just be used as a tool to help you. So make sure you don’t fall into this trap. Turn your compression pedal off every now and again, and make sure that you’re not letting your technique slip. 

it’s not always necessary 

It’s also worth noting that compression isn’t always needed, and in some cases, it’s the opposite of what you actually want. Compression pedals will even out the volume difference when you pluck hard or softly, which is great if this difference in pressure is unintentional. 

However, sometimes, you want the difference in volume to be present. A lot of guitarists vary the volume of different notes to give a certain effect, or to build up the intensity. Compression pedals will reduce your ability to do this.

Of course, you can alter the controls to prevent this happening. The best way it to lower the threshold, so that only really harsh frequency changes are evened out. 

Best Compression Pedals

So if you’ve decided that you like what you’re hearing about compression pedals, and you want to go ahead and get one, then you’re probably wondering which one to go for. 

I know when I was shopping for my first compression pedal, I was so confused by all the different makes and models and found it really hard to actually choose one. So to keep things simply, I’ve chosen my two favourite compression pedals to talk through, rather than just giving you a list of the top 10 that doesn’t really help you narrow down your choice that much. 

Keeley Compressor

This pedal was recommended to me by a friend who has played guitar for decades, and this pedal was recommended to them by several other players. If you really want a professional sounding compression pedal that gives you loads of control, then the Keeley Compressor pedal is in my opinion one of the best options to go for. 

I really like it because it gives you all the control you could need, but without being really complicated to use. You have sustain, level, blend and tone controls so you can do everything you could possibly want to. Plus you get a single coil/ humbucker mode switch to give you more versatility. 

It’s also got a really sleek looking design that looks great on my pedal board. You can check out the Keeley Compressor on Guitar Center

compression pedal

Boss CS-3 Compression SUSTAINER Pedal

If you don’t want to spend as much as you have to for the Keeley Compressor, then I think the Boss CS-3 is a really good option. It’s a bit cheaper than the Keeley Compressor, but gives you all the main controls like level (threshold), tone, attack and sustain, so you can really dial in the amount of compression you need. The only thing you don’t get is the pickup mode. 

One of my favourite things about Boss pedals is how robust they are, so they’re really great for gigging. Or just if you’re just clumsy like me and manage to drop it when you first open it out of the package! You can also find the Boss CS-3 compression pedal on Guitar Center with free shipping. 

More FAQs

So that’s pretty much all there is to say about compression pedals, but here are some more frequently asked questions that you might still have!

what is make-up gain?

So when you use a compressor, it reduces the volume of all the sounds that are above the threshold, so that they are equal to the threshold. This stops any harsh loud notes being heard. 

This causes an overall reduction in the volume you hear. To compensate for this, you can have make-up gain. This boosts the signal to prevent this overall reduction in volume. 

what is headroom?

This refers to the dynamic range of your signal. Basically, it’s the the difference between the quietest sound, and the loudest sound. 

So for example, a song with a lot of headroom will have really quiet sections and really loud sections. But a song with low headroom, will sound basically the same volume the entire way through. 

Compression pedals reduce the headroom, by squashing the signal. The smoothness they create is caused by them reducing the amount of headroom aka difference between the loudest and quietest signal. 

what does hard knee and soft knee mean?

Hard knee and soft knee, is the technical way of describing the attack control that you see on a lot of compression pedals. 

Soft knee is when the compressor pedal slowly begins compressing the signal, whereas hard knee, is when the compression pedal kicks in really quickly.  

 

So there you go! That’s the ultimate guide to compression pedals! I hope you’ve found this article helpful, thanks for reading. Here are some other posts you might find useful:

Heather

Hey, I'm Heather. I started playing an electric guitar when I was given a Squier Strat for my birthday around 15 years ago. I now own an acoustic guitar and several electric guitars including my personal favourite, a PRS SE Custom 24.

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