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Thanks for the info Scruffie. I'll try to find that layout...

I'm putting together the Azabache this weekend, can't wait to try biasing the FETs
+1 to LaceSensor for having a MicroSynth on your board!

It would be great if somebody made a PCB for the original Electro Harmonix Hot Tubes. I just watched the video for the new reissue version, and it sounded good. Only problem is that just like every new EHX pedal, it's been turned into a shrunken-down SMD version of something that used to be special. I've had no success with SMD-based pedals, they are always noisy and hissy. Plus they are just about impossible to work on if something goes wrong. Electro Harmonix should take a clue from the fact that their best designer, Howard Davis, won't even touch the new SMD-based stuff for mods.

My favorite Big Muff sound isn't from a Big Muff at all. The Electro Harmonix Micro Synth is like a Big Muff on steroids. It gives you the same heavy fuzz sound but with the added octave controls and sweep options. Most people think they are hearing a Big Muff on Smashing Pumpkins recordings, but the Micro Synth was used much more; and still part of their regular pedal board setup. It would be an interesting pedal to try to clone...

This will be next on the list! It has about one of the lowest part counts for a fuzz pedal pcb:  Just a 741 op amp, 4 ceramic caps, and 4 carbon comp resistors. Would be a great test ground for different op-amps, I'm sure they would have a big affect on the sound given so few parts.

*A good note for this circuit* Some schematics and suggestions say that you need to keep the battery ground separate from the ground of the rest of the circuit. This is not how the original circuit is set up and will result in a noisy, ear-piercing whine. Pictures of the original circuit clearly show the battery ground going to a switched jack, which of course makes a connection with your guitar cable ground and the chassis when inserted.

Taper does affect the sound of a pedal because the volume pot in most designs actually acts as a filter for different frequencies. In the case of the triangle knob muff, the volume pot acts as a high pass filter in conjunction with the final coupling capacitor. In an audio taper pot, the resistances are shifted from where they should be at different settings. So the circuit sees different resistances on each side of the pot than what the original design was based around, i.e., in a linear taper pot the resistance is 50/50 when the pot is set at half, whereas an audio taper is uneven. In the Op-amp version, the volume pot is directly connected to the tone pot, so it greatly affects the tone and gain when the resistances aren't correct.

I've built several different vintage Big Muff clones, and one of the most common mistakes I've seen on almost all schematics is using audio taper pots for volume controls. No version of the Big Muff ever used an audio taper pot in the original designs; they were always linear taper. This is especially critical in the op-amp version Big Muff. Putting an audio taper pot in the volume section kills the gain and shifts the tone stack frequencies so that it will never sound like an original. This common mistake is the main reason people always say the clones don't sound as good as the originals.