Pre EQ and Post EQ (effective differences?)

[robin watson]

Can anyone describe (in a practical way) how pre EQ is implemented in a guitar amp, preamp, etc., and what effect it has on say, overdrive tone, compared to post EQ.

My only conclusion (based on some experience with a Rocktron Taboo Artist) is that post EQ has a more 'pronounced' effect, whereas pre EQ is more subtle. As I understand it, pre EQ is used as a "tone shaping tool for overdriven tones", but can anyone be more insightful?

Cheers to everyone.

[stainlessbrown]

I'm sure someone will jump in if this isn't exactly correctly, but pre-eq essentially cuts or boosts the range of frequencies in the signal... the tone pot on a guitar is essentially an EQ device, with most being linear, so you have one giant slider for the range, lots of bass cuts the treble, the mids is a "happy medium" and full treble cuts the bottom.

If you're using EQ on the front end you're cutting and boosting before the signal is amplified which does "shape" the sound, however, there may be dynamics that you're not hearing at the front end which you not want to cut or boost.

Each layer of processing affects the original signal, either by eliminating aspects of it or introducing distortion/noise.

probably not the most scientific answer.

[boingoman]

Originally Posted by robin watson

As I understand it, pre EQ is used as a "tone shaping tool for overdriven tones", but can anyone be more insightful?

Cheers to everyone.

Hey Robin! Hope you are well.

I think you have it about right. It can be a tone-shaper or correcter, to say reduce the amount of low-end or problem frequencies sent to a reverb or distortion or compressor. Kind of like when you track vocals and use a low-cut before compressing. Then the post EQ can be used to EQ the effect.

It can also be used in more extreme ways. I do an acoustic piece where I play a harmonics over a bass line. I wanted some delay on the harmonics only, and wanted to perform it live. I used the pre EQ on an FX processor to cut everything below 400 hz in a delay preset. That way the bass notes never make it to the delay. It makes the sound much cleaner than post EQ did, because even if I rolled off the low end of the delay return, there were still artifacts from the bass notes hitting the delay.