These days there is no shortage of armchair experts who use the word "compression" in ways that can be confusing if you're unfamiliar with the term. I've often heard people describe modern music in general as over compressed, or I've heard people describe an overdrive pedal or an amplifier as having a nice tube compression. I've even had people advise me that some issue I'm having with my guitar sound can be solved by compression. But what exactly is compression and can a compressor pedal really help that much, or can some of this just be chalked up to placebo effect?
In my younger days all of this vague conversation around compression caused me to experiment quite a bit with compressor pedals and I'd like to help anyone who is a little confused about what compression actually is to understand what these pedals can do for your guitar.
What Is Compression: A Brief Explanation
In simple terms, compression takes the volume dynamics of anything being compressed (in audio production, you can compress vocals or drums or guitar or even an entire track) and evens them out. This means that things that are quiet become louder, and things that are comparatively quite loud will get quieted down a little bit.
There are some relatively ubiquitous terms used to describe some common parameters of compressors, however not all of these parameters are available as controls on a guitar pedal. Some guitar pedals might have only two control knobs that might have different names than the ones described here, but usually even in these cases the terms are synonymous with one of the following parameters.
Threshold: This describes the level at which the compressor will engage. Any signal that is quieter than the threshold level will not be compressed, and anything above the threshold will be compressed.
Ratio: This describes the degree to which your signal will be compressed. The higher the ratio, the more the guitar's signal will be squashed once it passes the threshold. While on a guitar pedal this sometimes appears as a knob and so an actual numeric ratio isn't visible, it can be thought of in the following way. A ratio of 2:1 means that for every 2dB of volume above the threshold, the compressor will allow 1dB of volume increase. A ratio of 200:1 means that for every 200dB of volume above the threshold, the compressor will allow for an increase of 1dB in volume.
Attack: This describes how quickly the compressor will act. A shorter attack time means the compressor reacts quickly, a longer attack time means the compressor reacts a bit later.
Release: This describes how long the compressor is acting on the sound. A quicker release means that as the note rings out, the compressor will back off. A longer attack time means that the note will remain compressed as it rings out.
Notably, some guitar pedals have a sustain knob. While it is best to consult the owner's manual for the specific pedal in order to have the most accurate understanding of what this knob will do on a particular pedal, it is often describing the threshold or ratio or some predetermined combination of the two.
Additionally, many guitar pedals have a volume or level knob. Again, while it is best to refer to the owner's manual, this is often an output gain control.
Finally, many guitar pedals have a blend knob. As always, reading the owner's manual for a specific pedal will provide the best answer, but this is usually a knob used to bring in some of the unaffected, uncompressed sound into your signal.
Compressor Pedals For The Guitar
Compressor pedals have been an undeniable part of the tone of some pretty iconic guitarists. Trey Anastasio from the band Phish has used a compressor pedal for a very long time, and you can find a compressor pedal near the front of the signal chain for just about every country guitarist worth their salt.
With that said, it might be surprising to learn that the overwhelming majority of compressor pedal circuits are based off of just one model: The Ross Compressor.
With just two knobs, this compressor is the most copied circuit on the market today. Some clones like the Keeley Compressor or the Wampler Ego Compressor have additional controls that give you greater control over the way the pedal affects your sound, but the circuit for the compressor is the same.
The Ross Compressor was reissued around 2019 (this may not be the exact year), however they are hard to find and a little pricey. Original Ross Compressors are in my humble opinion, too expensive to justify the purchase.
MXR Dynacomp
The Ross Compressor may be the most copied circuit out there today, but it wasn't the first. The Ross Compressor was actually an improved version of the MXR Dynacomp, a model still in production today and at a pretty reasonable price point.
Keeley Compressors
Robert Keeley of Keeley Electronics, who is well known for selling very popular modifications of some classic effects pedals by Boss and Ibanez, has also made some very cool tweaks to the Ross Compressor circuit with his line of compressor pedals.
This four knob compressor includes an attack control (the attack on the Ross and Dynacomp Compressors were preset) and a knob labelled "clipping". This clipping knob is really an input gain and allows the user to adjust the input gain so that guitars with high output pickups will compress the same way that guitars with low output pickups will without clipping the input.
Wampler Ego Compressor
The Wampler Ego Compressor is a favourite in the country world, and it includes one of my favourite additions to the Ross Compressor circuit, the blend knob. This is not the only Ross clone to include a blend knob, in fact the Keeley Compressor Plus also has one, but this is the first one that I remember seeing and was definitely the first one that I owned.
Why Use A Compressor?
Pros: There are lots of reasons you might want to use a compressor, and there's no way I can cover all of them, but I can briefly describe from my own experience what I like about them.
First, there is a tone that a compressor adds that is absolutely essential to certain styles of guitar playing. That feeling of a squashed note or chord fits so well in a country band or even in a funk band and it can really help to fit in in some of those settings.
Second, a compressor can be very helpful in settings where you want all the notes in your chords to sound even. While balanced chord playing is definitely something any guitarist can afford to work on, a compressor can help attain a certain type of evenness in your chords that can sound great.
Cons: While there are certainly benefits, there is always a down side.
First, the fact that many of the compressors out there on the market are clones of the same circuit means that many compressor pedals share the same issues. For me the most glaring is that they can add an unwanted amount of noise into your signal chain. Sometimes this can be controlled with a noise gate, or sometimes it isn't too egregious, but it is something to consider.
Second, in a live setting I sometimes find myself struggling with compressors. By virtue of the fact that compressors even out some of your dynamics, I sometimes find myself struggling for dynamic range in my playing when I'm using a compressor. This might not be a relatable experience for other guitarists, but it has been my experience. I should note however that this issue is often abated by the use of in ear monitors on a gig.
My Favourite Compressor
I'd like to end this post off by mentioning my favourite compressor pedal that I've ever owned.
The EP Booster by Xotic Effects is designed to emulate the sound of the preamp section of the Echoplex, which was an old tape echo machine that had a notably unique pre amp sound.
While this isn't intended to be a compressor pedal and it is only meant to be a clean boost, I have found that this pedal produces a really compressed tone in a very musical way. For anyone who is really fighting to find a good compressed tone I suggest checking this pedal out.
Thank you so much for checking out my thoughts on compressor pedals, and please feel free to reach out with any comments or concerns! As always, its a huge privilege for me to be a super small part of your journey with the guitar.
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