All Pass filter?

[ConsidertheBirds]

I'm currently attempting to design an overdrive pedal, and I'm looking for a more tube driven sound and not flat out distortion. I think I know how to get the gain I want with the op amp (I just have to do a little research as to exactly what components, but I have a somewhat general idea), but I was wondering what exactly an all pass filter would do in the circuit instead of a low pass, high pass or both. From what I understand it allows all frequencies to pass through at the same gain stage, but just changes the phase of the circuit. This is accomplished by three resistors, how I have seen all the resistors being the same.

So would it operate almost as a synthesizer effect on the pedal, would it just be compression of the overall sound, or would it be something beyond my wildest dreams?

Thanks alot

[PRR]

All-pass requires a reactance (L or C).

All-pass alone has "no" effect on audio. The ear is very insensitive to phase.

All-passes "do something" when you build-up a LOT of phase-shift, then MIX that shifted signal back with the original.

> I have a somewhat general idea

At this stage of your path, forget all-pass filters, except to copy a proven phlanger-plan verbatim.

[ConsidertheBirds]

Ah ok, so it would have no use in an overdrive pedal
I'll stick to the low pass and high pass  

Thanks for the help PRR