This Week on the Breadboard: The JHF-3 "Band of Gypsies" Fuzz

[Chuck D. Bones]

I really should have listened to the demos first. This thing is so bottom-heavy that Dunlop ought to call it the "Kim Kardashian Fuzz." Humbuckers? Fugeddabouddit! P90s are too thick for this biatch. I tried it with my Tele and the bridge pickup is still too boomy for my tastes. The dynamics, harmonic structure and note decay are pretty sweet. If Roger Mayer says this is what Jimi used at the Fillmore East on New Years 1970, I have to believe him. I'm not posting a schematic because the ones I've found have a few resistor values that seem sketchy. If anybody has one to trace, I'd be interested in verifying a few component values. The basic design is very similar to the Axis Fuzz. The JHF-3 kicks the gain up a notch by changing some resistor values and adding an emitter-follower 2nd stage. I have yet to find a good way to substantially reduce the bass response without changing it to the point that it's not a JHF-3 anymore. This thing might make a really good bass fuzz. I do like the basic design, so I haven't given up just yet. One cool feature of this circuit is I can change the last stage from Si to Ge with no resistor changes and the bias is still dead-on.

This is it with a Ge 3rd stage.

 

[fig]

I have a JHW-4 BOG. It doesn't seem especially boomy but I've never played it solo into the amp. I'll give it a go later and report back. *

I'd like to get the above breadboarded as well. Thanks dude!

*Edit: meant to say....apples to oranges though.

 

[Chuck D. Bones]

Can your pedal be traced? Or is it all SMD?

 

[Feral Feline]

Did someone say "Bass Fuzz"?

 

[fig]

SMD...the orange to the JHF-3s apple. I'll see if I can find one of those for a reasonable price.

Edit: $400 is seemingly the street price....seems a tad steep for a dozen components I have laying around, but I've learned one thing...you can't have mojo AND money....or was it you can't have money and....never mind, I don't want to go off-topic....I know how that sticks in yer craw.

 

[Chuck D. Bones]

After a few days of trying this and that on the breadboard, I have something I like.
I added a FAT switch up front and a TONE knob at the end.



I didn't change very much. Replaced the input cap with three caps on a toggle switch so I could tighten up the bass if I wanted. Reduced C8 from 22uF to 10uF to tighten up the bass a little more. I swapped R2 & R3 to make the clipping more symmetric. Try it either way and see which you like better. I swapped in a Ge transistor for Q3. Silicon sounds hotter. MP38A has a little less gain and has a smoother top end. Reduced R10 to improve the high freq response when FUZZ is dimed. Added the TONE pot. On the schematics I found on the 'net, the VOLUME pot is 500K. I see no reason for it to be that large other than to mimic the 500K VOLUME pot in the original Fuzz Face. Plenty of volume, a moderate amount of gain, smooth note decay. Excellent dynamics and touch sensitivity, good volume clean-up. Any high-gain, low-noise Si transistors will work for Q1 & Q2. You can use low-gain Si, high-gain Si or Ge for Q3.

 

[Chuck D. Bones]

Another Ge circuit for ya, Steve!

 

[fig]

Thank you......from Steve

 

[steviejr92]

Hey hey I have an excuse Tim! I was sorting out some GE transistors! Now Im ready for this bad boy!

@Chuck D. Bones What hfe for Q3 should I be looking for?

 

[fig]

I think they run around 40-50 hfe,

Edit: Small Bear says their lot tested 50-80 so...better ask Chuck eh?

 

[steviejr92]

I think they run around 40-50 hfe,

Well dang isnt that perfect.....the batch i just got in has a few candidates for that spot!

 

[Chuck D. Bones]

What hfe for Q3 should I be looking for?

I don't know if it matters much, I picked one at random for my breadboard. I measured it just now... HFE = 79 @ 1mA; Iceo = 200μA. These are not "magic" values. With no signal, Q3-C is around 5.4V. Again, not a magic number, just a ballpark to tell you the circuit is working. The bias point bounces around quite a bit when you play thru this circuit, that's normal.

 

[steviejr92]

Looks like Q3 isn’t picky on leakage as well.

Thanks for checking, that’s going to be my starting point when i breadboard this.

 

[Chuck D. Bones]

This circuit will accommodate a broad range of transistors for Q3.

 

[steviejr92]

Let me ask, the bias jumping around while playing tells me the circuit is very reactive to your guitars input. That should also translate to more harmonics correct?

 

[Chuck D. Bones]

Not necessarily more harmonics. The shifting bias causes the harmonic content to vary as the instantaneous volume changes. The effect is similar to amplifier sag.

 

[steviejr92]

Ahhhh that put it into perspective perfectly for me!

 

[Chuck D. Bones]

There is a lot going on in this circuit. I spent a fair amount of time experimenting on the bench and in simulation.

 

[fig]

DL'd.

 

[steviejr92]

There is a lot going on in this circuit. I spent a fair amount of time experimenting on the bench and in simulation.

I almost want to ask where a Jfet might be placed in a circuit like this…and if it would be a good idea?