Pre-Compression

    or I ain't gonna suck no more....


If you've ever heavily compressed a vocal, you know how you can hear the
compressor engaging just a bit as it bites down onto the vocal.
You can hear the compressor 'suck' the very first sound of the vocal.
We normally call this 'pumping' or 'sucking'.


No matter how fast you set the compressor it's gonna take time for
the compressor to sense audio level and then begin to compress it.

One of the tricks we used to eliminate this was to FIRST hit the Compressor
with the vocal signal coming off the Sync head (so this is BEFORE
all other tracks) and feeding this to the 'Trigger' (or key)
of the compressor, then feeding this SAME vocal delayed so that
it's back in sync with all the other tracks and then
feeding this to the Compressor's normal Audio Inputs.

Thus you get the compressor to 'pre-compress' BEFORE the actual vocal sound...
it's very cool, and damn 'smooth'.

The compressor first 'sees' the vocal level thru the 'trigger' or 'key' input
sets it's compression to the correct level, and IS ALREADY THERE -
at the 'correct level' BEFORE the vocal audio you're using.

Using a somewhat slow release time prevents the compressor from re-setting
itself before the vocal's actually finished.

You can do this set-up in a couple of ways.....

The simplest - but not the best sounding way is to set the vocal track into
sync and have all others in the normal 'repro' mode of your tape recorder.
That sets the vocal out of sync, and it will come up before
it normally should. MULT this signal into 2 points.
Use one to feed your compressor's 'trigger in' or 'key in'.
Use the other mult of the signal and feed it into your best digital
delay (or if you have a Studer with dual outputs you can select one
output to sync and the other to normal repro...) anyway, you feed the
out-of-sync vocal into the delay and set the delay so that this signal
is delayed exactly to where it should be if it were in sync with all the other tracks.

So now you've got the vocals back in proper place, delayed to where it should be.
But the compressor is 'seeing' the vocal signal right off the sync head
with no delay. So it 'sees' the vocal signal BEFORE the now-delayed vocal gets
to the compressor's audio input.
Now you set the compression level as needed, using of course the external trigger or
key. The compression level is thus pre-set by the time the delayed signal
goes into the audio input!
The compressor is still 'sucking' or 'pumping' but since the audio going through
the compressor is delayed when compaired to the triger signal, all the
compressor is going to 'suck' is the silence before the actual vocal signal.
So now you can heavily compress the vocal, yet get a very nice smooth sound,
without 'pumping'.

The BEST way to do this - what we used back in the late 70's, was to
record the vocal track onto another track of the multi-track recorder
and set that track into the sync mode, feeding that to the compressor's
'Trigger' or 'key' input, and then feeding the other track - played
back in the repro mode like all the other tracks - to the audio input of the
compressor. this is the PREFEERED mode, because it keeps you TOTALLY ANALOG!!!
You'll also find that this technique helps when you've got a vocalist with
a sharp first-attack, or who seems to 'ess' a lot.

Anyway, try this if you've not already doing it...
Oh and it works for gates as well... you can 'pre-open' a gated signal
so you don't hear the sound of the gate hitting the signal.
Again you need a slow release time...

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