Compression ratio and the channel strip volume

[rooted]

Hi,

I've been learning about compression, I know what it does (I hope I do) and know what the controls do. So, I have a kind of general general idea of what it's all about.

There is one thing that I'm really not sure about and that's setting the Ratio and it relationship with the volume of the channel strip.

I recorded some audio into Logic and noticed that when I turn the fader down on the channel strip there is still gain reduction in the compressor. I also noticed that when the channel fader is full you get the same amount of gain reduction (with the same ratio).

I would have thought that increasing the channel fader (on already recorded audio, in this case) would have an effect on the gain reduction, because I'm increasing the volume, and then the ratio would set the new volume/gain reduction?

The ratio is in effective a volume control?

And learnt that if the input level is 10 dB above the threshold and the ratio is 4:1, the output level will be (10 divided by 4) 2.5 dB (of course this figure will vary depending on the input volume). The thing is, if I increased the channel strip volume/input that should have an effect?

I did notice that on the actual channel strip volume that there is a difference in the peak level when the compressor is on or either bypassed.

Thanks in advance

 

[ido1957]

Pre-fader compression?

 

[mixsit]

...I recorded some audio into Logic and noticed that when I turn the fader down on the channel strip there is still gain reduction in the compressor. I also noticed that when the channel fader is full you get the same amount of gain reduction (with the same ratio).

The compressor is typically before the track or channel fader, this way you would set your comp for a give amount of reduction (it reacts to the various momentary ups and downs of the instrument or voce..) then you make your mixing blend moves with the fader on the effected signal. This would be called 'pre fader in the string by the way.

There is some utility to making mix level changes before (into) the compressor as well- but in this context more often this is simply establishing (or correcting for) a desired good nominal static track level. Generally this would be your (input) 'Gain, 'Trim or something you likely have in Logic similarly named.

The ratio is in effective a volume control?

Mmm nah.. You got the ratio math thing there, that's pretty much it.

I did notice that on the actual channel strip volume that there is a difference in the peak level when the compressor is on or either bypassed.

Sound like it must be working.