IC and Tranny recommendation

[mnordbye]

I'm designing an overdrive pedal at the moment, which will have 2 gain stages with a small switchable booster in front (in the same circuit). I'm looking for a nasty, heavy overdrive/distortion, preferably tight mids too. But don't mind that, i'm gonna make a NASTY distortion pedal, that's my only clue. 

Anyway, do you recommend a transistor for the booster and a dual IC (2 ICs?), which in general will make a good fit together. This is my first design by the way, so no ultra high-tech stuff, which i doubt i understand. 

Magnus N

[brett]

Hi
if you are going for high gain, you'll need to be carefull about noise and oscillations.  Low-noise ICs include the TL072 and NE5532.  However, the latter has lowish input resistance (which is probably a good thing for a single-purpose high gain pedal).  To prevent oscillation, place a de-coupling cap (0.1uF) close to the IC (use the search function if de-coupling is a new concept).  Also, keep the high amplitude output signals away from any in-phase low amplitude input signals.  Having "rat's nest" wiring helps due to the absence of parallel wires.

Any transistor-based buffer/booster at the front of a high gain circuit needs ultra low noise.  The MPSA18 is probably what you want. The 2N5089 is also good, from memory.

Clearly, you'll need some fancy filtering and hard clipping, but it sounds like you've go that covered.
Good luck and let us know how it goes.

[mnordbye]

Thanks for the reply Brett. Your suggestions sounds really interesting actually, the MPSA18 transistor is the way to go for the booster i believe. Never tried that one before.

As for the IC, i'll think i try the NE5532. Never tried that one either, so i guess it will be cool to try something new..

And yes, i'm planing on making it a high gain pedal, but i want the booster to take care of the gain stage pushing, so when on(i'm putting a switch to turn the boost stage on or off), the pedal will be a high gain distortion pedal, and when off, more like a heavy overdrive. Is this a good idea with the current selection of tranny and IC?

You say i need some fancy filtering, i guess you mean the caps and resistors always in the start of the schematic, those who prevent DC leakage and radio signals?

Magnus N

[mnordbye]

Any other tips and suggestions would be welcome too, by the way.