Ultimate Guide To
Guitar Compressors

The guitar compressor is probably one of the most intimidating and misunderstood guitar effects around.

It’s also one of the most useful pedals and a pro guitar player shouldn’t be caught without one. So, let’s have a look at the world of Guitar Compression Pedals and see just how versatile this small pedal can be…

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Written by

Jed Van Wyngaardt

So, what is compression?

To put it very simply, it reduces the dynamic range of the guitar. So, it slightly boosts the volume of notes you pick softly and brings down the volume of notes you pick a bit harder. So, you end up with a much smoother sounding guitar tone. That dynamic range can be adjusted with the RATIO control on most compressors.

It will give you more sustain and get rid of any harsh high frequencies because a compressor will put a rein on your signal.

What does compression actually do?

Compression is one of those effects that you will feel more than you’ll hear. At first anyway.

If you were to plug in a delay pedal, you’d immediately hear the repeats. Or if you plugged into a fuzz, you immediately be overwhelmed by woolly distortion! However, compression might need more of a trained ear because it’s not a sound effect, but rather a necessary adjustment to the signal.

Typical Controls On a Compressor

Threshold

This is the level where the compression will start to happen. If you set it high, it will catch the peaks (any harsh frequencies or jumps in volume). If you set it low, it will compress just about everything that goes through it.

Ratio

Also known as limiting. Will set how much the signal that goes above the threshold is compressed by. For example: With a ratio of 2:1 for every 2 decibels of increased input gain it increases output by 1 decibel meaning you get nice big clean headroom.

Attack

This will set how long it takes for the note to ring before it is compressed. So, a fast attack would be good for country chicken-pickin’ because you want all your fast hybrid picked licks to be smooth and even. A slow attack can make the compressor sound more natural.

Release

This is how long it takes for the compressed note to bounce back to being normal. You would adjust this for the same reasons as the attack. It’s worth experimenting with, but leaving a slightly longer tail of compression with a medium attack will give you a very natural sound.

Different types of Compressors

  • Optical – These compressors use a light bulb (or LED) to create changes in gain according to the incoming guitar signal. It then changes the gain by using the varying brightness of the bulb. So more signal will force more compression. This method will soften the attack and release of the compressor meaning you won’t get any harsh compression artifacts in your signal.
  • FET – This stands for Field Effect Transistor which uses a special type of transistor to vary gain. They emulate vacuum tubes in the circuit and are quite similar to how an analogue amp can emulate a valve amp (without the valves). They are regarded as very fast compressors and don’t colour the signal as much as other compressors can. A good example is the famous Universal Audio 1176.
  • VCAVoltage Controlled Amplifier is one of the most versatile compressors available. It can rapidly alter its gain level in response to different detectors analyzing the same signal. This is the one to go for if you want strict control over the signal and you can make it as fast and harsh or as gentle as possible.

Here's what Boss say about their VCA CS-3 Pedal

We asked Boss about what makes their CS-3 pedal unique. These are their direct quotes where they speak about the low noise floor and incredible sustain of their famous CS-3 compressor pedal.

  • CS-3 has low noise VCA design compare with CS-2 and this is core component of CS-3 sound.
  •  This VCA design realized low-noise and clear tone supported by advanced basic design of BOSS engineering.
  • Also, CS-3 has wider availability of sound making from limiter use, long sustain with clean tone and use as booster.

It’s worth noting that Boss did some of the earliest compact pedal compressors and their CS-2 was amazing for vintage compression sounds.

Why do I need a compressor?

What better way to answer this question than by asking Brian Wampler who designed the Wampler Ego Compressor?

‘ A compressor can be used to be really squashed like the 80’s and 90’s country guitar tones, but I see more and more people understanding that you can use it for much more. You can set it so you have natural dynamics, but very long, nearly limitless sustain which allows chords to ring out longer and notes in a solo to go on and on.

A favourite use of mine personally is to use it for solos so my “sloppy notes” sound much more fluid. You can also use it with the blend to just bring a bit more of a “fullness” overall to the character of whatever you are playing. ‘

And while we had him, we also asked What’s the best way to set up your compressor for a sound that is subtle and only kicks in when needed (without losing volume)?

Brian Wampler: "For us, the key is in that blend knob. You can run the attack and sustain controls wherever you feel sounds best. Then, roll the blend all the way down and slowly blend in that compressed signal to the sound you are looking for. Then, simply adjust the volume to what sounds right to your ears."

I asked Simon Keats, the head designer from Origin Effects (Boutique Compressor Effects) the same question, and he gave me a fantastic juicy answer. It was so good in fact, that I have dedicated another blog post to his thoughts on compressors. you can read it by clicking HERE!

Where does a Compressor go in the signal chain?

As with all things guitar, there are NO RULES. But there are some vague guidelines that you should start with and logically, you would be better off putting the compressor first in your signal chain. Compressors will amplify any signal going through them (remember they push up the soft signal, and squash the loud) which means if you run any noisy pedals before your compressor, then that noise (it may be mains hum from the pedal, or noise from a poor power supply) will be made louder going into your amp. Not ideal for live use and definitely not ideal for studio!

An alternative to first in the chain, is after the overdrive and distortion pedals. This will reduce the ‘squash’ that it causes but will even out your rhythm and lead tones.

We got a direct quote from the engineers at BOSS Japan asking them the same question and this is what they said: ‘The compressor generally put before overdrive/distortion pedal also post wah pedal, but you can use CS-3 more creative way thanks to wide tonal adjustability and low noise design. There are no single rule, so we would like to ask users to try to find their own best setting.’

Shop Compressor Pedals!

So, which Compressor should I get?

Ah, the age old question. So which one do I get? Well ultimately, that’s down to you. You have to experiment with them and decide on which one to get depending on how much control you want over your compressors. Don’t watch videos on how they sound. You have to feel how it affects your playing. Get into the store and try it out for yourself!

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