Re: Harmonic Perk & Jerk SMD/TH hybrid

Posted by PMowdes on
URL: http://guitar-fx-layouts.238.s1.nabble.com/Harmonic-Perk-Jerk-SMD-TH-hybrid-tp31209p31674.html

induction wrote

If I could only have one dirt pedal, it would be this one, no question. My favorite by a long shot.

Two circuits on one board: Select between the Interfax Harmonic Percolator and the Escobedo Harmonic Jerkulator, and Si, Ge, or no clipping diodes. I started with the values in the linked schematics and fooled around on the breadboard until I optimized each circuit to my preference. Neither circuit is exactly stock, but there are lots of different Percolator schems around, so that doesn't mean much. The topology of the circuit is what makes this thing do what it does, and I haven't changed that. The Percolator needs a low gain PNP germanium, while the Jerkulator wants low gain Si PNP. I adjusted caps and resistors to taste, feel free to do the same. I also added a 10k input resistor to kill the (very loud) buzz when you turn your guitar volume all the way off.

I didn't have any 47u tantalums, so I used pairs of 22u tants. You can use 47u if you have them. Legend has it that it really wants tants in that spot, so who am I to argue. I can't swear it will sound any different with regular electrolytics, though.

Both circuits are very sensitive to input volume, and the volume knob cleanup trick works so well that I probably won't put a Gain control on mine, I'll just control it from the guitar. Depending on input volume it goes from tight clean-but-dirty overdrive, through distortion territory and into splattery spongy fuzz. The Si and Ge circuits sound pretty similar at low input volume, but diverge quite a bit at full gain. The clipping options give more or less volume and a slightly different flavor. It's loud as all hell with no clipping diodes. You might find the Ge circuit quieter than the Si circuit, even with Ge clipping at full input volume. That surprised me, but didn't bother me much.

This one is verified by me, and I can't get enough of it.

What size box do you recommend??  I managed to get the Perc into a 1590B but it was a fiddle,  and this has two extra switches.

I might play it safe and go for a 1590B