Description
I have seen many posts on the forum recently asking about compression. Questions posed are:
What is it?
How do I use it?
And what use is this sustainer pedal ?
Compression is a way of limiting an instruments or a waves dynamics to make it easier to listen to. If
something contains quite bits and loud bits and the loud bits are drowning out the soft bits, then if you
selectively reduce the volume of just the loud bits enough you will be able to hear both.
An example of this would be a film on the TV that has a bit of quite whispering dialogue followed by
an explosion. You turn the volume up to hear the quiet bit and then after being knocked backwards by the
volume level of the explosion, turn the volume back down.
A compressor in this instance acts as a volume control automatically turning the volume down during
the loud bits. This can also allow the average volume to be louder boosting the quiet bits and making
them more audible.
How do you use a compressor?
A studio compressor will typically accept line level signal from say a sound desk. This is NOT the
same as Hi-Z guitar level signal fed into your guitar amp it is a little hotter. Consequently if you want to
plug your guitar into a rack mounted compressor you will need a DI box to bring your guitar signal up to
line level. If you are using a stomp box compressor then don't worry about it, I'm sure the unit was
designed to take Hi-Z signal. It would be OK for a line level loop in say an amp except that like many
other effects it doesn't work well in a loop as you need to effect the whole signal (like a distortion pedal).
Compressor Controls:
Threshold: This is the level at which the unit will begin to alter the signal being fed to it.
Ratio: This is how much the compressor will reduce the signal once it passes the user-
defined threshold. A 2:1 ratio means that for every two DB over the threshold the signal is the compressor
will apply a 1DB reduction in gain. A ratio of "infinity" acts as a limiter meaning that no matter how much
more signal come in beyond the threshold the threshold will never be passes.
Attack: This control effects the time in milliseconds after the threshold has been passed
before the compression takes effect.
Release: This control effects the time that the compression is applied after the signal has
fallen back down below the threshold.
Level: This is another gain stage and allows you to compensate for a reduction in overall
volume.
Now something that really gets my goat. On many stomp boxes these compression controls are called
by different names in order to make the unit more appealing to a guitarist. This generally only ends up in
confusion and has made me feel like catapulting the odd stomp box through the nearest wall.
Example:
On a Boss CS-3 the "level" is actually a threshold control and the "Sustain" is actually the ratio control
with the attack and tone controls as labeled. Personally I think this stuff is difficult enough to understand
with out messing around and playing musical chares with the labeling of the controls!
Compression can be used on anything from a violin to a vocal. It is often used to tighten up drums
and clarify vocals. It is also often applied to a final mix to tighten everything up and make everything
more audible. However if you use too much you can flatten all the life out of your instruments and kill
your mix stone dead. So, use your ears and listen to that cymbal. How long dose it normally ring out for?
If it is over compressed there will be a marked reduction in its tail and everything will sound very flat and
monotonous.
Lesson Info
