Installing a fuzz in a jazzmaster

andare said:
Is this a J Mascis JM that you stripped? The vibrato plate looks to be closer to the bridge than normal.
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I built the body myself actually! I used a template that had the vibrato route location but I'm not sure if it's standard or not, could be a little closer.
 
Very cool. I cringed even when spending $75 on the American Pro bridge, but its lack of sustain leaves a lot to be desired. I'm curious about other options outside the absurdly ugly Mastery bridge.
 
That’s pretty cool. That’s not terribly expensive for a gigging musician. I stopped that about 10 years ago, now it’s just expensive but not out of the question. Nice guitar.
 
You don't actually need a pulldown on the output here. If the volume pot comes after the output cap like that, it functions like an output pulldown resistor itself.

And example where you would need an output pulldown is on something like the Rangemaster where the cap comes after the volume control, which is not a very common arrangement. Without R9 in the below circuit, there's nowhere for any leaking DC to go when the pedal is disengaged. When it's re-engaged, you may hear a pop because there's DC potential on the output.

With R9 included, leaking DC will flow to GND through R9 when disengaged. The pot in the Fuzz Face serves this same purpose.

1751498907639.png

But if you've already wired an output pulldown in there, it shouldn't make much of a difference if you want to just leave it in.

If you still get more noise than you're happy with, you might try putting a very small resistor (~10-47 ohm) in series with the 25uF electrolytic. It can add some stability and should have only a tiny if not negligible effect on gain. At least one fuzz face circuit from a big name manufacturer wires a 10 ohm series resistor into theirs.

In the original Fuzz Face circuit, there may be a small amount of resistance there even with the fuzz pot all the way up due to the residual resistance between lugs 2 and 3, depending on the potentiometer. ESR of the cap can be enough to make a difference too.
 
^ the pop we are dealing with is a result of power being applied with the on switch. Most pedals are always on, but to save battery life, as it is mounted in the guitar, power is switched on as well. I believe there is a voltage spike as power is switched on, partially bc C3 is leaking more DC to ground than is ideal. Therefore it should be changed for a film. What do you think?
 
AmplifiedPartsTom said:
If you still get more noise than you're happy with, you might try putting a very small resistor (~10-47 ohm) in series with the 25uF electrolytic. It can add some stability and should have only a tiny if not negligible effect on gain. At least one fuzz face circuit from a big name manufacturer wires a 10 ohm series resistor into theirs.

In the original Fuzz Face circuit, there may be a small amount of resistance there even with the fuzz pot all the way up due to the residual resistance between lugs 2 and 3, depending on the potentiometer. ESR of the cap can be enough to make a difference too.
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Thanks, I'll try that the next time that I open it up! It would go where I drew the red arrow on this schematic, right?

Screenshot 2025-07-02 at 7.53.02 PM.png
 
A 25u film is going to be big and not cheap
That's the smallest one I see on mouser.
That being said, I have no idea why that cap is speced so large on a battery fed circuit. I think 1u film would be fine. Maybe even smaller. You're not really concerned about ripple with a battery.
I wonder if you could use an on-on-on switch to engage it.
Pos 1 - no power/clean
Pos 2 - PCB powered/muted(input switch but output floating)
Pos 3 - both PCB switched/fuzz position
Just that little bit of break before make could provide a split second mute to cover up the transient of the pop.
Down side, you could accidently mute your guitar, but you'd also have a kill switch. I feel like this could be done with a DPDT on on on, but I can't wrap my head around it at the moment. The you're into 4 poles, which aren't expensive but can feel clunky
 
I've been looking at tantalum caps to replace the electrolytics as film caps of the appropriate values seem to be huge in size. Would that be a good choice? I haven't used tantalums before, but I understand they are polarized.
 
Yes ragamuffin, you have the location of the small resistor right.

The 25uF value of that cap is important, dropping it down to 1uF would make a large difference in sound. That cap bypasses the emitter resistor to maximize gain, and for signals of high enough frequency the impedance of the capacitor can be considered close enough to 0 ohms that the emitter is effectively grounded for those signals. But the impedance of capacitors increases as signal frequency decreases, and at a certain point the impedance becomes large enough that it's not negligible. It effectively creates a high pass filter where the cutoff is dependent on the capacitance value. With 25uF, only the lowest guitar frequencies will be noticeably attenuated and even then it's a fairly small amount. With a 1uF cap it would be much more drastic across the whole frequency spectrum.
 
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