Sunday, 16 February 2014
Joe Davisson Shocktave
For some reason none of us got my CJ Downbox v2 layout to work. That was a bit of a mystery since the schematic was working correctly on my breadboard, but even though the layout did not have any errors, the flip-flop simply refused to work. I had taken the layout down a long ago and almost forgotten about the whole thing. Until a few nights ago. I was watching some DS9 episodes and skimmed through my ever growing schematics folders. I noticed this one. It's Joe Davisson's Shocktave, dated 2005. This time, as we had one utter failure with the similar design, i decided to build it first and post it if it would work. And what do you know. It works. Low octave fuzz not completely unlike the MXR Bluebox, but with a lot lower parts count. Tracking goes wild very easily, but you can tune the mix control to have quite massive and cool low octave walls with this circuit. Output level doesn't feel luggish, so for all of you who enjoy dirty and noisy low octaves, here you go.
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Found a demo clip of this one:
ReplyDeletehttps://archive.org/details/ShocktaveFuzzDemo
I've built this circuit quite a few times, it is a great one.
ReplyDeleteI've built this circuit quite a few times, it is a great one.
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ReplyDeletehello, IS THERE ANYBODY WILLING TO EXPLAIN HOW THIS CIRCUIT WORKS? :) i simulated it and i don't understand what makes flip-flop section behave like an octaver. does it reset it or what? and how? also i'm willing to discuss how to improve it and post my own schematic which i believe works better (op-amp preamp and some mods). the trouble is, I DON'T LIKE TRACKING, and want to improve it, but don't know how because it can't figure out how it works!
ReplyDeletedid you ever figure it out?
Deletehttps://i.pinimg.com/originals/0e/f9/91/0ef991ff747b0f40ad4db4a603185d08.gif
DeleteSo here's the schematics (also, I don't understand why people don't post them with the vero layouts) I've eyeballed it and it looks about the same although I think it has a failure in it.
So the first 2 transistors on the left are a common collector buffer and a common emitter inverting amplifier with an adjustable gain. On the right side there's an astable multivibrator which would oscillate around 71Hz if we powered it constantly. But we don't, we're giving it power at the positive half waves of the input, and it's supposed to wake up in it's opposite state every time. When its right transistor is conducting it'll shunt the output, when the left one the half wave goes out through the rightmost 10k resistor. Now what I think the error is, the transistor between the amp and multivibrator. Its base and emitter are switched up, plus the diode the other way around. That way it'd be a common collector buffer capable of powering the astable, while the diode would charge the 470nF in negative half waves..
Build it and love it.
ReplyDeleteCurrently thinking of building this crazy beast that is based off of it.
http://www.davidrolo.com/effects/giant-hogweed/
Heh I just got a PCB the other day from David. Just waiting for my order of PCB mounted pots... hurry up Thailand Post.
DeleteHow do you think this would sound on bass. Looking for a sub octave fuzz but haven’t seen anything yet
ReplyDeleteWell, I built it for bass specifically and it sound good, if you're into NES-style analog grinding kind of thing. :D Somewhat similar to Boss OC-2 with filter removed. Very "electric" and wild, lots of high frequencies, like pulse square wave with no filter on.
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ReplyDeleteHi,
ReplyDeleteBuilt, but getting no signal. Been bashing my head against this all day. Is this definitely verified? I've checked layout so many times now mine matches.
Don't matter sorted. I tapped a wire into the output and kept placing it along the signal path. Got two transitor 2s base and it stopped after that...
DeleteFound the smallest short in the vero that even the multimeter wasn't picking up. Removee and all good now.
Sorted... Tapped a wire into the output jack and kept placing it through the signal path. Signal stopped after transistor 2 base...
DeleteFound the smallest ever short even the multimeter didn't pick up. Gone and all working now. 3 hours that b*****d cost me
Hi. :) I symphatize with you, I also had many similar issues while building pedals. It was all good while I had free time, but later it became really annoying, I would spend ages finishing one pedal. Glad you figured it out. :)
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