I have a Leeds Fuzz and it sounds exactly like the one in this video:
This sounds to me a bit different than a lot of the vintage Super Fuzz videos out there, and I've come across some information that suggests why that could be.
I haven't build a BYOC Leeds, but I've looked at the design. It's pretty much identical to the treadle type Univox SuperFuzz, including the NOS transistors. With a little care, I don't see any reason why it wouldn't sound identical to a Univox.
The only comment I'd make is regarding the trimpot setting instructions in the BYOC manual. They say to "set it so that it produces the most noise", and then say that this is going to be somewhere near the dead center position. This is actually NOT what the original engineers had in mind. The trimmer was added to compensate for the minor differences between production transistors that caused imbalances in the differential amplifier stage used to produce the octave effect. These imbalances were the reason that many of the earlier Shin-ei and Univox pedals varied widely in the amount of background noise they had. Univox added the trimmer so that the circuit could be balanced, regardless of the differences between the two transistors.
I'd recommend hooking the finished pedal up to a guitar and amp, and then tweaking the trimpot for MINIMUM hiss without playing. Unless the transistors are widely mismatched, this will be very near the center position.
Another clue why it sounds a bit different is in this manual for another Super Fuzz clone:
All of the vintage Super-Fuzz pedals featured a special two-transistor circuit that would add an "octave up" tone to the normal fuzz effect. For this reason, these pedals are often referred to as "octave fuzz" effects. Your Fuzz pedal features this same circuit.
In the original Shin-ei and early Univox pedals, both transistors in the octave circuit were balanced. Univox later added a trimmer resistor, which allowed the octave circuit to be intentionally unbalanced, making a variety of tone variations possible. Unfortunately, the extra resistance from the trimmer changed the bias of the octave circuit, and also changed it's tone. For this reason, it's common to find some of these later pedals with the trimmer removed, and jumper wires installed.
We've added the balance trimmer to the Fuzz, so you can get the same tone as the later Univox pedals. However, we've also reduced the size of some other resistors in the circuit in order to compensate for the trimmer, so you can also get the same tone as the earlier Shin-ei and Univox pedals.
So, there are two slightly-different-sounding Super Fuzz variants out there. The Shin Ei and early Univox versions without the trim-pot, and later Univox versions with trim-pot.
I think the BYOC instructions could be updated to explain the trim-pot calibration more accurately, if the information about it not being supposed to be where it's noisiest, but quietest near the centre is correct. Also, maybe the information about jumpering the trim-pot can be added so that people can choose to either build the original Super Fuzz or the revision.
Also, I'm interested in trying jumpering the trim-pot to see how it sounds that way. Which holes would need to be jumpered to do this?
Joined: Mon Jun 06, 2011 6:59 pm Posts: 2225 Location: Fayetteville, AR
It's been a while since I built this one, and maybe I don't fully understand the question. But, I seem to remember the trimpot being there to adjust for part tolerance and it was just a set-and-forget thing. The octave effect on this isn't a real pronounced effect like a Foxx TM or Octavia - it's more of an overtone that comes in on single notes around the 12th fret or so.
To do that on the Leeds, just remove the trim pot, jumper the two PCB pads at the top of the trim pot space together, and jumper the lower, centered pad to either one of the remaining open pads.
Joined: Sat Mar 04, 2006 9:15 pm Posts: 7662 Location: Ohio
This is a perfect example of why it’s a good idea to keep a set of test leads around. You could easily short the trim pot out of the circuit with a pair of these. They make demoing a mod you’re considering a breeze.
To do that on the Leeds, just remove the trim pot, jumper the two PCB pads at the top of the trim pot space together, and jumper the lower, centered pad to either one of the remaining open pads.
Cool. Thanks for the clarification!
Stephen wrote:
This is a perfect example of why it’s a good idea to keep a set of test leads around. You could easily short the trim pot out of the circuit with a pair of these. They make demoing a mod you’re considering a breeze.
Couldn't you just turn the trimpot all the way to zero resistance? Maybe I'm not catching how it's working in the circuit.
I just gave this a try. It sounds good, and it stacks really nicely with other pedals. However, when the pot is set to its lowest, there's also created the gating effect that the BYOC instructions caution about:
"There are rumors circulating the internet that this trimpot controls the amount of octave effect that mixes in with the fuzz. This is somewhat true, but keep in mind that if you used this trimpot as such, it can cause an unusual “noise gate” effect at the end of each note on certain settings."
If that's akin to not having the trim-pot in the circuit, does that mean that the gating effect is a part of the original Shin Ei fuzz sound? If not, then what is different with the original one?
Connect both 22k resistors to ground leaving out the trimpot completely. That is what some of the schematics show anyway. The trimpot on either side of the sweep will basically offset the ground, so all the way to one side will ground that resistor, while increasing the other one to 32k and vice versa. Doing that should give you an early circuit sound, before the inclusion of the balancing trimpot.
Connect both 22k resistors to ground leaving out the trimpot completely. That is what some of the schematics show anyway. The trimpot on either side of the sweep will basically offset the ground, so all the way to one side will ground that resistor, while increasing the other one to 32k and vice versa. Doing that should give you an early circuit sound, before the inclusion of the balancing trimpot.
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