Hey RG, very good explanation of how to use a compressor
Absolutely on the money IMHO! Now I'll get a little more technical. Fundamentally, we need to understand what a compressor does, and to some extent how it does it (and most important, how this affects your gain structure (which RG covered in his post)). In this context, a compressor is a device that modifies the dynamic range (lowest level to highest level) of an audio signal. You could describe it as "squish" the signal, so lower level sounds are louder and higher level sounds are softer (the result of this can be turned up or down in the mix (output of unit, desk settings), but the dynamic range has been reduced (by the compression ratio (and threshold, where does the compression start to work/affect the signal))).
Rule of thumb (audio engineer 101), less is better!! I'm not a big fan of compressors, but they have their place as a very useful tool (unfortunately not well understood, and often used badly).
Why do you want to use a compressor (live sound, set to peak limit so you don't blow speakers), in a mix typically coz you want things to sit nice and tight together (kick, bass), vocals (whatever). Guitar, as RG says why, the tubes are doing it for you, well not quite the same, tube clipping (while very similar (in some ways) to compression) actually isn't compression. The other thing about compressing guitar (and again similar to using high gain clipped signals) is some use it to make up for sloppy playing (and ditch the dynamics along the way). Hey, grab an acoustic and get your dynamics back
Putting a compressor up front: so squish the dynamics (signal) coming off the guitar, has output knob so can boost output to preamp input, so louder squished signal now entering preamp (
). If you want to use a compressor for a particular effect, go for it (for me anything more than 1.5:1 is way too much except I'll entertain "absolute" PA peak limiting at 8:1).
All that said. I do use the MP2 compressor for my clean sounds... As RG says, use your ears...
@Soloist, yeah lots of compressors in those days, trying to "squeeze" it onto vinyl.. I still tried to use as little compressor as possible LoL.