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Compressors, for guitar - a simple guide Featured

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If you are anything like me, for the longest time you treated compression as a big ‘meh’ and didn’t understand why virtually all guitar players need it. Yes, I did say that, virtually all guitar players need it. I thought that compression was something country and funk players used, so I thought I didn’t need one when I was younger… this all changed when I got a BOSS BE-5 that had a compressor in it (a CS-2 I think) and I thought it’s only job was to fill some of the holes within my sloppy solo playing.  I couldn’t be more wrong, I couldn’t have been using it more incorrectly if I tried. But, it lit a little fire in me to discover what compression was really for, in terms of guitar tone and how, when used with a degree of subtlety, it was the most important pedal to own.

Compression probably IS the most valuable item in your toolbox and one that should be used appropriately. By appropriately, I mean almost all of the time, but in the right way. However, the true key is working out what ‘appropriately’ is…. to truly understand what compression is, you first need to understand all the different elements of compression. More importantly, what they do and how they work together.

The initial logic of compression is to reduce the audible distance between the quieter parts of your playing and the louder. It will make all aspects of your playing heard, the softer will come up and the louder will be reduced. You could say it’s limiting the dynamics of your playing. A great example is when you are watching TV and the person whispering will be loudest thing you can hear… it’s been compressed so you can hear it. Transfer that to your playing - you still want your softer parts heard clearly, you don’t want them to disappear in behind everything else but also, you don’t want your loudest moments overtaking everything. Reducing the amount of space between the softest elements of your playing and the loudest will make your tone more user friendly to just about everyone.

Let’s look at some of the more common parts of a regular guitar-based compressor to understand what each control does. 

THRESHOLD
This is the point at which the compressor activates. So, until you hit the desired level, the compressor will be dormant. The higher the threshold, the longer it takes to kick in. The lower the threshold, the quicker the compressor activates 

ATTACK
This is the amount of time the pedal will take to fully compress the signal. The faster the attack, the quicker the compression. This often causes confusion as a lot of compressors attack faster when the knob is CCW and slower at CW. So, the more attack is when this control is turned down! The classic sound for this is country, that instantly recognisable vintage country squish comes from a fast attack, with the more modern style of country being much slower. 

RELEASE/SUSTAIN
The opposite of attack. The longer it takes the note to be released back to its uncompressed state. So, if you are looking to sustain your notes, the release is what you need to tweak to bring the level of those notes up. Release usually happens anywhere from about 50ms up to several seconds, depending on the unit… this has to be treated with respect though, as this is the knob that will quickly send you into feedback – which at times can be great, but at others, can be horrible.

RATIO
Quite often this is missing on a regular guitar compressor, it has been defined by the engineer at design stage at the optimum place for guitar. However, on more comprehensive pedals it will be there. The ratio is the mathematical aspect of the compression… 1:1 is no compression, 2:1 is when it goes over 2db over the threshold limit the compressor brings it back to one over the limit of 1db – for 10db it brings it back to 5db and so on. When considering the ratio the simple guide is that the higher the first number, the more compression will be added.

3:1 is light compression, 5:1 is medium, 10:1 is getting strong and 20:1 is getting severe. You can get ∞:1 (infinity) which would be ‘limiting’, the hardest compression you can get – a hard shelf of “none shall pass”. 

KNEE
The knee is the shape of the compression and it’s called the knee in order to give you a visual representation of what is happening. A hard knee will be like a leg that is fully bent, as the signal hits the compression level it cuts it off almost at a right angle, the attack is instant and you really hear and feel it. A soft knee will place a curve in there so, as it approaches the limit, it will start to attenuate and level out – looking more like a knee half bent. If the knee is soft enough, you will hardly feel or hear it, until it is turned off.

How to use a modern compressor pedal
A lot of people have tried compressors before and not liked them. Quite often it is because they tried one of the standard basic units that don’t have a lot of control to the finer aspects, or the all-important blend control. Something with a basic “attack” and “release/sustain” setting will often be frustrating and anything but musical. A lot of older compression units also coloured the tone as well (they had a tone of their own) which was delicious if you liked it, but horrendous if you didn’t. Let’s face it, when you are considering a compressor you probably have your tone pretty well thought out… from the strings and pickups on the guitar, the guitar itself, the pedals, the cables, the amp, the speakers, the speaker cab… you like it and more often than not, you don’t want to change it all by adding one pedal. This is where modern compressors come in as they are - and yes, here it comes - they are transparent. They don’t colour your signal, they don’t change your tone, they just compress. It’s my opinion, and we all know what they are worth, but a perfectly compressed guitar signal is one you don’t know is compressed until you turn the compressor off and everything just disappears.

One of the most important aspects of modern compression is something I mentioned above, the blend control. The blend is what is also known as parallel compression – a favourite of the studio engineer. If you have a blend control on your compressor, there will be two, obvious, sonic reference points. 100% compression path and 100% non-compressed path. Straight up the middle will give you 50% compressed and 50% dry. As most compression is heard at the point of attack, you bleed in the blend to reduce that, that feel of your note being compressed. Once that balance of blend is set, the initial squish of the compressed signal is not really heard. You can still feel it, but the rest of the note duration is compressed. You get more sustain, more control, more stability, but without that hard first hit… as the natural signal dies out, the compressed signal overtakes giving you a fatter, longer lasting and fuller tone.

Once you have balanced your compression, you then have the whole “where do I put it in the chain” dilemma. Most people put it up front, so by the time your signal hits your gain stages everything is on the level. This is usually the case when the player is leaning on the heavier side of compression. A lot of players like it after gain stages, this is very handy when using it as an effect rather than as a regulator. Kicking in a subtle amount of compression after your gain stages makes everything fatter and wider, it almost feels like you are going into a cooking tube amp when you are not… the down side of this, obviously, is that any floor noise from your dirt pedals will then hit the compressor and be brought up, this can make your rig much noisier and harder to control. Also, the higher amount of gain (clipping) in your path will add compression as well, so a compressor might not be so obvious a requirement for heavier players (although it’s great for making your chuggachugga sound more CHUGGACHUGGA).

And don’t get me started on multiband compression… you can choose which part of the frequency you want to compress… it could be the lows, the highs, the high mids… absolutely everywhere. This is the reason I want 5 compressors in my rig. But that’s just excessive. Or is it?

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