a take on the venerable Tube Screamer

This circuit is largely identical to the original Ibanez Tube Screamer circuit, with the exception of one of the clipping diodes being replaced with a Vbe multiplier whose voltage drop is set by a trimmer or potentiometer, allowing the user to set the amount of asymmetry in the clipping. With the voltage drop across the transistor set very high, the signal is not clipped at all until the op-amp itself maxes out, resulting in very hard clipping. The unfamiliar-looking section to the right of the ciruit is a tube-amp emulator I ripped off from somewhere. Likely won't be built into the final design.

The 5532 is probably not the best suited op-amp for this job; the MC33078 (or any op amp that is actually specified to work with 9v between the rails and reasonable audio characteristics) would probably be a better choice. The TL072, with its propensity for phase reversal under hard clipping, might yield some interesting results. In all likelihood, however, the choice of op amp will be inaudiable; battery life will be the most impacted factor.