Superfuzz - Bells & Whistles?

[Ginsly]

I'm looking to build a Superfuzz, either modding an existing pcb or starting with a known vero/perf layout.

Some things I'm curious about:

- adding a pot to replace the Mode (Scooped/Mid-Bump). Pretty standard mod, it seems.
- adding a switch to remove the Upper Octave (Basic Audio has this down, it's incredible)
- adding a switch to go from FY-6 to FY-2 (Fredric Effects does this)
- adding either a global voltage starve or transistor bias knob (the latter seems tricky on this)
- a diode switch of some sort?

Essentially, a "kitchen sink" Superfuzz. I'm not sure I've seen some of these explained, like the Octave-Off switch. Same for the FY-6/Fy-2 mod - both of these are possible, as BA and FE have used them to great effect on their versions.

It would be great to incorporate a starve or bias control to either squash the signal or degrade it in a fun way. Maybe this just doesn't work with the FY-6 circuit, though - not sure I've seen it done.

I'd love some pointers! If there is a good pcb or vero starting point for this, I'm all ears. If some of this is unrealistic (bias, etc) feel free to shoot me down!

Thanks all, looking to be more involved here - great, great resource.

[Ginsly]

I came across this DIY build locally which features some additional controls, but since I don't know who built it I don't know how they operate! Got me thinking about those other BA and FE versions, though...

[FiveseveN]

Sounds like a noble endeavor
Some extras I added to mine:
-I opted for independent volume for the scooped & flat outputs instead of a blend, same number of pots
-Variable LPF on the input
-Continuous (a)symmetry control instead of an octave switch
-Clipping pot to control the influence of the clipping diodes

You could put the bias control on the input transistor if you go for the classic topology instead of op amps like I did.

[Mark Hammer]

Everything after the phase splitter (transistor with 10k resistors on the collector and emitter) tends to be identical across the many different commercial fuzzes that descended from the Superfuzz.  It's the front ends that differ. The Royal, Acetone, HOney, Kay, and Superfuzz tend to have slightly different front ends and have slightly different sounds.  The Foxx is not identical to the Superfuzz, but a big part of its ultra-reliable octaving IS its front end.  If you want to go all out, consider mods that would let you vary the front end.

[Ginsly]

Sounds like a noble endeavor
Some extras I added to mine:
-I opted for independent volume for the scooped & flat outputs instead of a blend, same number of pots
-Variable LPF on the input
-Continuous (a)symmetry control instead of an octave switch
-Clipping pot to control the influence of the clipping diodes

You could put the bias control on the input transistor if you go for the classic topology instead of op amps like I did.

Whoa! Those sound very cool indeed. I'm not quite at the point of replacing transistors with op amps, so I'll take a look at replacing Q1's collector resistor with a pot (of what value, I'm not sure!).

Everything after the phase splitter (transistor with 10k resistors on the collector and emitter) tends to be identical across the many different commercial fuzzes that descended from the Superfuzz.  It's the front ends that differ. The Royal, Acetone, HOney, Kay, and Superfuzz tend to have slightly different front ends and have slightly different sounds.  The Foxx is not identical to the Superfuzz, but a big part of its ultra-reliable octaving IS its front end.  If you want to go all out, consider mods that would let you vary the front end.

I absolutely love the Foxx AND Kay, and I like that the FTM already has the Octave on/off switch baked-in from the beginning. Full disclosure, I'm 6 months into building and certainly biting off more than I can chew. Still, I have to challenge myself and try some wild things. I'm starting to be able to determine WHERE the front end of a schematic is, so your explanation of where the phase splitter is actually helps a lot.

I found a mod of the Behringer Superfuzz (close enough?) that just removes a 1uf capacitor and puts it on a switch in order to go between Octave/No Octave. Removing the upper octave makes the SF noisier (same with the FTM, I've found), which is why I started thinking about a bias/gate/starve that might reduce noise and possibly create an even splattier, synthy fuzz.

I think I need *slightly* more hand-holding with this stuff, but I really do appreciate it and it's helping me learn very quickly.

[Ginsly]

If anyone could help me navigate adding a switch to go from FY-6 (6 transistors) to FY-2 (2 transistors) and a switch to simply cut the octave from the FY-6 I'd be thrilled.

I'd also love to add a transistor bias knob, but I'm not sure which resistor on which transistor I'd need to replace with a pot...

I haven't been building long, so this kind of guidance helps me in future builds too. I really appreciate it!

[Matthew Sanford]

Mind posting the schematic you're working from for lazy people like me that don't want to search?

[Mark Hammer]

The FY-2 and FY-6 are different beasts.  Going from one to the other is no simple matter.  Actually simpler to build both and use a switch to go from one circuit to the other.

As for cancelling the octave (not that it's as strong an octave as the Foxx Tone Machine in the first place) the mod involves cancelling one of the two phase reversed copies of the signal from the phase splitter.  The transistor after the "Expander" control, with a 10K resistor on both the emitter and collector is the phase-splitter.  Breaking the connection between the emitter and the cap immediately after it will remove the octave.

[Ginsly]

Mind posting the schematic you're working from for lazy people like me that don't want to search?

Good call, my apologies! Here are a couple - one is Aion's schematic which is only slightly tweaked, and the other is the basis of a pcb someone gave me which has further mods.

The FY-2 and FY-6 are different beasts.  Going from one to the other is no simple matter.  Actually simpler to build both and use a switch to go from one circuit to the other.

As for cancelling the octave (not that it's as strong an octave as the Foxx Tone Machine in the first place) the mod involves cancelling one of the two phase reversed copies of the signal from the phase splitter.  The transistor after the "Expander" control, with a 10K resistor on both the emitter and collector is the phase-splitter.  Breaking the connection between the emitter and the cap immediately after it will remove the octave.

Gotcha - thanks so much, Mark. I had the feeling going from FY-6 to FY-2 was not as easy as going from Tonebender MKII to MKI.V. I'll shelve that idea for now! Fredric Effects must have both circuits in one box in order to do that: https://fredric.co.uk/nouveau-super-unpleasant-companion

Great, great input on removing the upper octave! Sounds like I would simply put a SPST on/off switch between Q3's emitter and C8 on Aion's schematic. Now that I think about it, SPST on/off may not be the correct switch... hmm. I've never dealt with a polarized component on a switch, so I have to figure out how best to set this up...

If I'm successful with that, there is another problem that pops up - noise. I've found that things get much noisier when I remove the upper octave from a Foxx Tone Machine or Superfuzz (based on John Lyons' incredible version). I've found that playing with the FTM's Q2 collector resistor helps a bit, as does adding a pot right after the power supply to starve the whole circuit - plus, it creates some very interesting sounds!

I'm not sure I've seen a Super Fuzz with either a transistor bias knob or global starve. The starve seems pretty straightforward (add a pot to the +9v signal coming into the pedal - right?), but I have no idea where a transistor bias would go... I'm VERY curious about this, as I think it might help reduce noise and create some strange textures...

[Electron Tornado]

Good call, my apologies! Here are a couple - one is Aion's schematic which is only slightly tweaked, and the other is the basis of a pcb someone gave me which has further mods.

In the Aion schematic above, look at the notch filter and R24 and R25. Try changing the 22k resistor for a 25k linear pot. I used the notch filter section for a tone control in another pedal. I did swap the positions of the 10k resistor and the 25k pot. I also changed the C12 cap to a 0.0033uf. Made an interesting tone control.

[Ginsly]

Good call, my apologies! Here are a couple - one is Aion's schematic which is only slightly tweaked, and the other is the basis of a pcb someone gave me which has further mods.

In the Aion schematic above, look at the notch filter and R24 and R25. Try changing the 22k resistor for a 25k linear pot. I used the notch filter section for a tone control in another pedal. I did swap the positions of the 10k resistor and the 25k pot. I also changed the C12 cap to a 0.0033uf. Made an interesting tone control.

Thanks much, I'll certainly take a look at that! Any thoughts about the transistor bias control situation by chance..? Seems like no one does it to the FY-6, there must be a reason for that...

[Ginsly]

Well, looks like someone asked which Superfuzz transistor/resistor to look at when incorporating a Bias knob, and RG Keen said this:

"You're not going to like this.

None of them do the fuzzing in the same way that the fuzz face works. The fuzzing is done by the back-to-back diode clippers and to some extent the full wave rectification in the almost-a-differential-pair."

Eek. Sounds like what I'm hoping to do might not be possible.

Any circuit wizards wanna see if they can crack the code?

[FiveseveN]

Do you have a breadboard?
Replace the 1st transistor's collector R (47K) with a ~100K pot and see what range of effects it provides. Adjust to taste.

[Ginsly]

Do you have a breadboard?
Replace the 1st transistor's collector R (47K) with a ~100K pot and see what range of effects it provides. Adjust to taste.

I plan to breadboard it very soon, so thanks for the input! Why Q1 over the others? Would you recommend placing a resistor in series with the pot to protect it?

[FiveseveN]

Why Q1

Besides the last (recovery) stage it's the only one whose job is to provide voltage gain. Q2 is a follower, Q3 is a phase splitter, Q4 & Q5 do the rectification etc.

resistor in series with the pot to protect it

The emitter resistor will limit current flow through the transistor (and consequently the pot). I wouldn't expect to find useful sounds at the lowest extreme of the pot's setting so you might want to add one for that reason (to limit range).

[Ginsly]

Why Q1

Besides the last (recovery) stage it's the only one whose job is to provide voltage gain. Q2 is a follower, Q3 is a phase splitter, Q4 & Q5 do the rectification etc.

resistor in series with the pot to protect it

The emitter resistor will limit current flow through the transistor (and consequently the pot). I wouldn't expect to find useful sounds at the lowest extreme of the pot's setting so you might want to add one for that reason (to limit range).

Great info, much appreciated! I'll give it a go!