What Is A Compressor?
A compressor just is a device used to regulate the dynamics (volume) of a source signal (audio).
It works by effectivly stopping the signal exceeding a value (maximum volume) determined by the operator (you).
If you were to classify compressors in regards to effects units, it would belong to the
dynamic processor family as opposed to time-based effects processor (such as reveb, delay, flangers).
Setting Up Your Compressor:
Before you start ensure you have connnected your compressor/limiter to mixer via the inserts.
- Begin by adjusting the compressor's threshold until the peaks start triggering compression.
- Now
adjust the Ratio as desired (depending on what your recording) ...we have now found our starting points, now you want to adjust (fine tune) ratio & threshold together until you have the sound your after.
- Time to move on to the
attack and release... The attack will change how long it takes before the compressor kicks in (each time it is triggered by exceeding the threshold), and release controls shape how the compressor 'feels' after it has kicked in (the release will determin now long the compression effect will last before the cycle ends).
- Finaly
adjust the output gain to compensate for any difference in volume that has occured due to the compression effect.
- Make use of your
bypass buton (if you have one) to check the original level, your looking to have created a
new average volume, so now you want to bring it up/down to aproximatly the same level you started with.
Things Worth Knowing:
The following are just a few suggestions (starting points even) to put you in the right direction, ofcourse what music/sounds you record will effect how the compressor reacts and thus how the final sound will be so keep that in mind. Also dont forget to keep an eye on your output gain control (if you have one) when dealing with harsh compression.
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Compressors can be set up to act as
limiters, the only difference between the two devices being that the limiter will have faster responses (shorter attacks = more effective limiting), if you want to set your compressor as a limiter make sure your settings are as follows: Inputgain=zero, threshold=zero(or or -1db ), ratio=10-15:1(or as high as it goes), attack=short,release=short-to-mid, output gain=zero.
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Suggested ratios: bass guitars around at 4:1, soft vocals around 2:1, heavy vocals around 4:1, acoustic guitar 2:1, electric guitararound 5: 1, percussion (shakers etc) around 2:1., synth lead (with reverb) around 5:1.
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Fast attack would be more prefferable for anything that has
sudden peakse,
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Slower attack is good for sound sources that require a a little
punch before the compressor begins flattening flatening the sound (such as kicks when you want a little ckick at the begining or more impact), I also find a really slow attack nice on bassline or synth pads when reverb unit is used via inserts (not send/return).
Common Compressor Types:-
FET, Compressors attempt to emulate valve compression characteristics but more reliably than valves can. FET compressors are apparently nice on drums. (but i havent checked).
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Optical (opto), as the name suggests they implement light sensitive circurtry. They have slower response times than alternatives - this can be for the better or worse depending what you are recording. If your looking for a dedicated compressor for vocals or anything that needs slow attacks you may find an Opto compressor;'s characteristic 'sound' better for your needs.
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Valve, Every one is familiar with the term valve compressor even if they dont know exactly what a valve is.. but you dont need to know how it works all you need to know is they are tempremental (the longer its on the more pronounced the effect), pronce to breaking if transported alot and generally more expensive... But for some reason they just seem to sound a little warmer, this is most likely due to their higher noise levels. (FET compressors can have higher S/N ratio)
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VCA, Voltage Controlled Amplifier compression is very precice and its another one of those does what it says names that well... does what it says ^_^.
Its internal circutry has less noise/colour and responses are very high making them very precice and therefor flexable devices all round.
Additional controls etc:The following functions/controls are not nessesary in a compressor but worth while knowing about, if you have them.
Bypass - Bypass often gets forgotten completely and results in a lot of scratching of heads when at a later point and asking questions like 'why is that track so quiet when it was so loud an hour ago' or 'why is this acoustic guitar distorted? ..I thought I had lilited it. The bypass function lets you compare what it sounded like before and what it sounds like now (post effect), if you didnt have bypass function you would be constantly plugging then unplugging they compressor or repeatedly reserting the controls.
Bypass also means you can permanantly connect your compressor to your mixer if used alot and not have to worry about damaging the socets through wear.
Side-Chain - Side-chaining is a technique that is widely used in music production, especialy electronic music. Sidechaining is basically getting one source to control another. so it could be compressor#1 tells compressor#2 when to trigger, or it could be oldskool synthesizer#a tells compressor#b when to trigger.
Warmth etc - these are not really anything to do with the actual compressor just additional things to add a little character to the sound... it could be a valve emulating transistor circut, or a subharmonic exiter effect process, it really depends on what you own.
Gate - If your lucky your compressor will have a built in gate, which will help clean up your recording (at least the dead air). ^_^ ...The gate will completely halt any sounds that do not exceed its threshold from passing (being heard), if it has varible controls (attack release) they work in the same way as the compressors attack and release do but they are unlinked (work independently of each other).
