Powderkeg

[cdwillis]

This is a new fuzz circuit I've been working on lately. I haven't reinvented the wheel, but sounds pretty cool and you can coax a few different sounds out of it. Looking at the schematic you'll see it's a cool tonebender mkII/III and big muff hybrid. You have an attack control that adjusts how much input signal enters the first gain stage. Bias controls the bias (surprise) on Q3. The tone stack is a Russian big muff style tone control so you still have a decent amount of midrange with a decent sweep from bassy to trebly.

With the attack below noon and the bias above noon you can get some more Led Zeppelin or Hendrix style tonebender/fuzz face type of tones. It cleans up pretty well as long at the attack isn't up too high. Turning the attack up over noon with the bias above noon gets your a more big muff sounding tone. Turning the bias down under noon makes it sound a little spittier and as you turn it down you get into the velcro fuzz territory. The lower the bias the more you may need to adjust the attack to maintain signal. Lower bias will also have lower volume which you can compensate with by turning up the output volume.

 

[cdwillis]

I forgot to add these ksp06 transistors are all 122hfe.

I messed up and used a b100k pot for the bias. The bias pot was unusable except for the last 10% of the sweep. Rather than deal with trying to remove it and put in the correct b10k I soldered a 10k resistor across the outside lugs for about 9k total resistance. The bias works over the entire pot range now, but the sweep is a little weird compared to the b10k pot on the breadboarded version.

 

[Laundryroom David]

That looks very cool. On OSH?

 

[jwin615]

Awesome stuff! Thanks man for sharing!
How does it play sandwiched.with other pedals? Seems like input and output impedance is extremely variable.

 

[Feral Feline]

+1 Thank you very much for sharing — Awersum Schtuff

 

[cdwillis]

Awesome stuff! Thanks man for sharing!
How does it play sandwiched.with other pedals? Seems like input and output impedance is extremely variable.

I've put my Boss tuner in front of it and there isn't really a discernible difference with the buffer in front or just the guitar going into it. It might be a little brighter, but it would be hard to tell in an A/B. Maybe if I had the buffer on a switch instead of having to switch jacks around I'd notice an immediate difference. One of the goals was to be able to use it with the tuner or other buffered pedal in front. The output stages are the same as a Big Muff so it should react the exact same as a muff would with anything else after it.

That looks very cool. On OSH?

I got these made at JLC PCB, just used the purple pcb option there. I have a few more pcbs if anyone wants one just DM me. This uses the pedalpcb drill template for the pots and jacks.

 

[BuddytheReow]

Is there something special about the transistors you selected or were they just in your drawer? I'm interested in this circuit, but don't have those parts.

 

[cdwillis]

A while back I sorted all the silicon npn transistors on tayda by price then I looked at the data sheets to see which ones had the lowest hfe. These ksp06 transistors were the lowest I measured out of the lot. The were consistently 120 to 130 hfe. I haven't tried any higher gain transistors here, but they'd probably work fine. The 100 ohm emitter resistors on q2 and q3 help keep them in check. You might want to drop the q2 collector resistor down, but I'm not sure.