A compressor doesn’t wobble like a chorus or echo like a delay, so its spot on so many pedalboards can seem like a mystery. The good news is the idea behind it’s simpler than the engineering talk makes it sound.
It borrows the same trick studio engineers use to even out a vocal or a drum kit. Two controls do most of the work.
This guide defines what a compressor pedal is and walks through what each knob does. We also cover why guitarists reach for one and how to pick a compressor pedal if it’s your first.
Let’s start with what the pedal actually is.
What Is a Guitar Compressor Pedal?
A guitar compressor pedal is used to increase the sustain of a note and reduce the dynamic range of your playing. It’s responsible for making the sound from your electric or acoustic guitar louder and more present.
It does this by “compressing” the signal, much like an old studio recording compressor. Those studio units were designed to make vocal recordings sound as loud and powerful as possible, and a guitar compressor applies the same idea to your instrument.
The compressor pedal is a great way to add flavor to your sound. It’ll make your guitar’s volume louder, but it also brings out the natural character of the instrument.
What Are Guitar Compressor Pedals Used For?
So what does a guitar compressor do? A compressor works by reducing the level of your loud notes. It doesn’t do this all at once or chop off the amplitude peaks.
Instead, it works gradually and evenly, depending on how high the sustain knob (called sensitivity on the MXR) is turned.
The amount of reduction is set by the compression ratio:
- A 1:1 ratio is no compression at all. No matter how hard you hit the string, it comes through the amp at exactly the volume you played it. At 1:1 the compressor accomplishes nothing, so you still play with the full dynamic range of 1 to 100 and how hard you play translates directly to how loud the amp is.
- A 2:1 ratio means that once the signal rises above a certain threshold, the volume of the spikes is cut in half. Set the compressor to 2:1 and a note you play at 100 will sound like a 75 through the amp.
- A 3:1 ratio reduces the spikes by two thirds, and so on. At 3:1, playing a 100 sounds like a 66 through the amp. In other words, the loudest you can play is 66 while the softest you can play is still 1.
To put this in context, suppose the quietest note you can play on a 1 to 100 scale is a “1” and the loudest is a “100,” and you set the compressor to kick in at “50.”
Because a compressor reduces peak volume, it also has a volume knob (often labeled level) that you can use to raise your baseline. In other words, it shifts the position of the “1” upward by turning up the quiet notes.
So if you increase the level until your “1” becomes a “20” and set the ratio to 3:1, all of your playing lands somewhere between a “20” and a “66,” and never gets louder or softer than that.
Reducing the amplitude of the peaks while raising the loudness of the softer notes has the overall effect of “squeezing” your dynamic range. If you dial up both the volume and the sensitivity, no matter how loud or quiet you play, it’ll always come out around a 50.
Dynamics lend a lot of character to your playing and phrasing, but heavy compression is useful for things like staccato funk chords. For most playing, though, you usually only need a small amount.
The reason you don’t just turn up the amp is that the amp sits after the compressor, so it raises the peaks as well as the quietest regions. It simply makes everything louder.
The same is true in reverse: when you lower the volume knob on your guitar, you lower both the peaks and the quietest parts, so everything gets softer together.
The volume knob on the compressor is different because it compensates specifically for the fact that the compressor has reduced the amplitude of the peaks. The peaks themselves stay limited thanks to the interaction between the sensitivity knob and the volume knob.
Why Use a Compressor Pedal for Guitar?
I often use compression as a boost. If you set all of the knobs on the pedal to 10, you can get a really long sustain that also adds a little volume on top.
The trade-off is that it can also make the sound muddy, so the notes don’t ring as clearly, especially if you’re already running a lot of gain from your amp or another pedal.
Another thing to be aware of is the amount of noise it can add to your signal, particularly when it’s boosting gain. Even so, compression is one of the nicest effects out there and one of the most adaptable.
It works with a clean jazz sound just as well as a prog rock or metal tone. The best advice is to try one and see how it fits your playing style.
Is a Compressor Pedal the Same as a Compression Sustainer?
Yes, they’re basically the same thing. “Compression sustainer” is just another name some manufacturers use to highlight that the pedal increases sustain as part of compressing the signal.
Functionally you’re looking at the same effect.
How to Choose a Compressor Pedal
For a newer guitarist, choosing the right compression pedal is a real challenge. It isn’t always easy to tell whether you’re buying a quality product, and there are a lot of options to wade through.
Below are the main factors worth considering before you buy your first compressor.
Budget
The first thing to think about is your budget. If you’re just beginning to play, chances are your budget won’t stretch to an expensive pedal, and that’s fine.
There are several good options that work well for beginners.
On the lower end, a Boss or Ibanez model is a safe bet. They’re fairly affordable, they don’t gouge you on price, and they’re generally solid quality that’ll last a long time.
In the mid-range, the MXR M-102 is a popular choice that many players consider the best compressor for beginners, and the TC Electronic Nova is also worth a look. In both cases you’re getting a decent product for the money.
If you’ve more cash to spend, the Keeley and Carl Martin compressors are widely regarded as some of the best ever made and they hold their value well, which matters if you ever decide to resell.
Capability
The next thing to consider is the pedal’s capability. The lower the gain, the less it affects your tone.
That isn’t always what you want. If you love your distortion, you may not want to dampen it with a compressor.
But subtle compression can be extremely helpful in other situations. For example, if you want to keep your pick attack from spiking early in the signal chain, a compressor can smooth that out, and if you simply want to keep your overall level consistent, a compressor handles that too.
Luckily, most compressors are versatile enough to fit a wide range of situations. Some use a gain knob instead of a level knob, which can be handy if you’re already known for a heavier sound, and those tend to push more of the signal.
If you’re like me, though, you’re probably looking for a compressor that works across many different settings.
Type
Type is probably the most confusing aspect on the market, so it’s worth understanding. Traditionally there are two broad styles: the dynamics compressor and the equalizer style, sometimes called a compressor envelope pedal.
The dynamics style is very transparent and works in a way that adds almost no coloration to your tone. If you want something that stays out of the way of your sound, that’s the style to look at.
The equalizer style is much more interactive with the signal. It usually has a bit more gain than a dynamics model and is less transparent, but it has the advantage of being more versatile precisely because of that tone interaction.
Frequently Asked Questions
Where should a compressor go in the signal chain?
A compressor is usually placed early in the chain, right after your guitar and any tuner, and before drive or modulation pedals. Putting it first lets it even out your raw signal before anything else shapes it.
Some players prefer it after drive pedals to tighten up an already distorted sound. There’s no single right answer, so experiment with both positions and keep whichever sounds best to you.
Do acoustic guitars benefit from a compressor pedal?
Yes. Acoustic guitars have a wide dynamic range, and a compressor helps tame the loud peaks of strumming while lifting quieter fingerpicked passages.
This makes the instrument sit more evenly in a mix or through a PA.
Use a light setting so you keep the natural character of the acoustic. Too much compression can flatten the lively, dynamic feel that makes an acoustic sound good in the first place.
How much compression should I use?
For most playing, a little goes a long way. A modest amount smooths out your dynamics and adds a touch of sustain without obviously changing your tone.
Heavier compression is better suited to specific jobs like tight funk rhythm, country picking, or long sustained leads. Start subtle, then add more only if the style you’re playing calls for it.
Can a compressor pedal replace a boost pedal?
A compressor can add a small volume lift, especially with the level knob turned up, so it can act like a mild boost. That’s one of the reasons players keep one always on.
For a big, clean jump in volume to push the front of an amp, a dedicated boost pedal is the better tool. The two effects overlap a little, but they’re designed for different jobs.
Final Thoughts
A compressor pedal is one of the most useful and flexible effects you can add to your rig. It evens out the volume of your playing, adds sustain, and brings out the natural sound of your guitar, all of which can make a noticeable difference whether you play clean jazz, funk, country, or heavy rock.
The controls can look intimidating at first, but once you understand the relationship between the ratio, the threshold, and the level knob, dialing in a sound becomes much easier. Start with light settings, listen for how the pedal smooths your dynamics, and adjust from there.
If you’re ready to pick one up, match the pedal to your budget, the amount of tone interaction you want, and the style you play most. Try one in your own signal chain and you’ll quickly hear why so many guitarists keep a compressor on their board.
