Tonebender to Supa Fuzz conversion

[bifbangpow]

Is it true that I can make a Marshall Supa Fuzz clone by building the tonebender but replacing the 4.7uF's with 10uFs?  Is that really all I would need to change? Also, which tonebender version are we talking about? The two knob? three knob? NPN silicon? PNP germanium?

[antonis]

Shouldn't be easier to just compare side by side their respective schematics..??

[Electric Warrior]

We're talking about the MKII.
The Supa Fuzz and the Sola Sound/Vox Tone Bender Professional MKII were the exact same circuit, all made by Sola Sound, but sold under different brand names. Apparently Sola Sound dropped their own brand name in favor of Vox early on, which is why the number of circuit variants for these is rather limited. Most (but not all) of the Sola Sound units are MK1.5s which were modified to MKII specs (known as the "small board" units because of the smaller MK1.5 circuit board they're built on). These don't have the cap between input and ground, which is why they're a bit brighter sounding.

The Marshall Supa Fuzz with the 10µF caps is a variant that was most likely made by Marshall - after Sola Sound had stopped making MKIIs. These don't have the cap on input either. I've experimented a bit with putting caps in parallel with the 5µFs, but it didn't seem to make a difference. Making the cap on input switchable would probably be more useful. You could also try switching the 0.01µF caps to 0.015µF - which is another common circuit variant. They're supposed to be a little thicker sounding.

There are schematics with different bias setups out there. Don't let that confuse you. OC75 and OC81D transistors both came with 10k on Q1's base and 47k on Q2's collector. More often the OC81Ds came with 100k in both positions. The ones with 100ks are biased to the same voltages as the ones with 10k/47k, though. The transistors must have been less leaky, so they had to make up for it by using larger resistors.

Here are some voltages from my vintage unit for reference:

Battery: 9.67V
Q1 C -9.02V B -0.03V E 0V
Q2 C -0.17V B -0.08V E 0V
Q3 C -8.44V B -0.17V E -0.11V

Q1C is a little high in this one; 8.5V would be closer to average.

[bifbangpow]

awesome thanks! Very informative.
also love t rex.

[Electric Warrior]

Glad I could help! Let us know how it goes.