Frequency response of Compressors

[Vivek]

In a compressor pedal, Is it normal to cut bass before signal enters the compressor stage

and then boost Bass after the compressor stage


While still seemingly leaving a considerable treble boost in overall frequency response ?


Here are the graphs I got while trying to analyse the ROCKMAN X100 compressor

Highpass before the compressor stage




Filter after the compressor stage




Overall frequency response of Initial Bass cut + final Bass boost

[StephenGiles]

Probably normal for Tom Sholtz.

[mictester]

If you plot the inherent sustain of each string of your guitar, you'll probably find that the low E sustains several times as long as the top E. The shaped response is to try to counter this, thereby giving each string about the same amount of sustain at the output of the compressor.

I've used this sort of frequency response to even out the drive to a clipper - you'll be pleasantly surprised at the improvement in "string definition" and how much more "playable" the effect is. You can always straighten out the response afterwards.

I often apply frequency response manipulation before a distortion stage - roll off the top for the smoothest "Big Muff" sound, for example. If you try adding a basic Baxandall stage before your favourite clipper you'll like the range of useful tones you'll find.

[GFR]

Some common strategies:

Cut bass before, restore after - if you're trying to avoid distortion (for example OTA's can't handle lots of input voltage, cutting bass will help bring it down).

Boost highs first, cut highs after - to reduce hiss when the gain is fully open.

There's also the matter of the frequency shaping of the signal that feeds the envelope detector.

[Mark Hammer]

Think of that tone-shaping as a kind of pre-compression compression.  In other words, it is an attempt to even out the overall amplitude of the guitar signal across the fretboard/strings, such that the rectifier is following similar amplitudes, no matter what string or note one is picking.