How does a Prescence or attack Control work???

[ejbasses]

How does a Prescence or attack Control work?

A friend let me borrow his behringer bass driver clon and though i dont like the tube emulation that much, I was wonering how the prescenc controle work. Its sort of adds a lot of top end to ny tone.

I want to build something like it but i dont want the tube emulation just the presence control that makes my signal sound realll sharp. So.... how do i build one?

[Mark Hammer]

The presence control on tube amps was a means of controlling the amount of negative feedback applied from the output.  In the early tube amp days, there was a desire to keep distortion under control, and the way to do it was to provide negative feedback from after the output transformer back to an earlier point in the power amp stage.  Eventually, it dawned on people that if one provided negative feedback for only part of the signal - specifically the high end - and that if you varied the amount of it, you could get sounds varying between something that was smooth (more negative feedback) and something that had bite (less or even none).

I suspect the Presence control you are dealing with is not at all the same thing since there is clearly no output transformer involved at all, and nary a tube in sight.  In such instances, what often gets called "Presence" or "Attack" is really more in the realm of a resonant boost in the upper treble range.