Newbie Rack Question...

[ditnoj]

Howdy,

What is a "side chain"? I'm looking for a preamp/compressor chain and
have run into this term. For instance, a compressor says it has a sidechain for
de-essing (I know what that is) and ducking (clueless).

Little bit of help this way, please..

D out ITNOJ

[Creepy]

Think of sidechain as a way to control an compressor or noise gate from something other than the audio at the input.

For instance, if you had a noise gate, and wanted to use it on a tom (drum) while tracking, you could hook up a trigger to the tom (like maybe a piezo tweeter! ) and hook the trigger to the side chain Return. Now the gate will only open when the tom is hit. As you know, snare drum bleed on a tom mic can sometimes be louder than any actual tom hit, so using a trigger is a great way to assure that the gate only opens when the tom is hit, because the Threshold on the gate is working off of the side chain Return, and not the input to the gate (which would be the tom mic in this case). Works very well I think.

On a compressor, you could hook up a eq on the side chain (side chain Send to the input of the eq, eq output to the side chain Return) and do Frequency Dependent Compression (de-essing is one use for this, but there are others!!! Like for plosives too!). On the eq, you would boost the offending frequency that you want to compress, and cut all other frequencies. In this way, the compressor's threshold is only responding when the offending frequency is present (which is may not be on many parts of the track). This is a great way too to compress selective notes on a bass guitar! The way this works is that the audio at the input of the compressor is routed to another device (the eq in this case) and that device manipulates it in some way. Then the manipulated audio is fed back to the Return of the sidechain. The threshold of the compressor is only reacting to the audio at the input of the side chain, and not the input of the compressor now. But, the audio that passes through the compressor is of course not manipulated like the the audio in the side chain, it is only manipulated by the compressor. Get it? That is why it is a "side chain", because it works along side the audio through the device. The side chain becomes the control track per se. It is a very cool idea, and is a very good trick that has a lot of uses if you think about it. You could create a lot of headroom while mixing by running your kick drum to the side chain return of a compressor on a bass. The bass would only compress when the kick drum hits! (think about that Mettalica sound! ). This is a very old trick actually, but one I never see home recording folks talking about, probably because it never really crossed their mind. If you think about it, you can increase the overall volume of the kick drum and the bass guitar because now the bass guitar and the kick drum, when played at the same time, won't be adding their accumulative volume to the overall mix! Get it? So let's say that you have your kick drum peaking at -.5 dB on the master meters, well, the bass guitar coupled with that would mean that you would have almost a doubling of power, which would mean that you have to decrease your overall mixes volume almost 6dB just because the kick and bass guitar playing at the same time are making the master meter shoot over 0. So, by causing a certain amount of gain reduction on the bass guitar ONLY when the kick drum strikes, a louder overall volume can be achieved! I am all for that brotherman!

As to your question, it is certainly a good thing if a compressor has side chain capabilities. I personally would be disappointed if a compressor didn't have it.

I am a Creep!