Tonebender MkII and Marshall Supafuzz

[tjmicsak]

I see the only major difference in these two circuits are changing the input and attack electrolytic cap values from 4.7 uf to 10uf.
Would that be a worthwhile mod to have the caps switchable, or are the value differences going to sound pretty much the same anyway?
The only other value that is different is the bias resistor for Q2 -which on the BYOC MkII uses a 47K instead of the 100K that an actual MkII schematic shows (just like is shown for the Marshall supafuzz), so looks like BYOC already leans their MKII towards the supafuzz anyway. Plus the BYOC uses OC75 in place of the infamous OC81D that are now a thing of legend only, so the trannys are also in line with the Supafuzz.
That is all why I wonder what difference it would likely make to turn the circuit into a full stock clone of the supafuzz with the caps.

[tcobretti]

I'd bet that bias resistor will affect the sound more than those caps.  4.7u is a huge cap, so 10u is just even huge-r.  However, that bias resistor could shift the bias of that transistor enough to make a difference.

But now that I think about it I doubt there's much difference between the two aurally.  I have typically found that while there may be a sweet spot in biasing, if you are slightly outside the sweet spot the resistance can be a pretty broad range and it's pretty much the same sound.  So a 47k may not be enough to really change the sound substantially.

If I were curious, I'd pull the caps and resistor in question from my MkII.  Then I'd solder in a socket for the caps and a trimpot for the resistor.  Then I'd plug in different caps and listen for a difference.  If you can't tell an obvious difference between the caps it probly doesn't matter, and then I'd tweak the pot to taste.  I guess you could wire up temporary switch just for comparison's sake on the caps; it'd be easy enough, and you could just take it out when you have your answer.

[Electric Warrior]

The resistor values of the two should be identical. I believe only the OC81D units had 100k resistors at Q2's collector and Q1's base.
Note that the Supa Fuzzes with 10µF electrolytics usually have no capacitor from input to ground.

Earlier versions of the Supa Fuzz were identical to the MKII.

[Electric Warrior]

btw, larger power filter electrolytics were used in later MKIIs. In some they used two of the 25µF caps in parallel, others had 50 or 64µF electrolytics there.
and some MKIIs had 0.015µF caps instead of 0.01µF.

[tjmicsak]

Today I did a little experimenting with the .01uf shunt cap. At first it seemed way too much high cut but I soon found I used a .1uf. When I did use the correct value it makes a difference that you can hear only faintly through headphones so I was actually planning on increasing the value as they did, by having this high cut shunt cap on a switch to use as a pregain setting as stock for humbuckers or add the cut for single coils. So far it works great for this but just too minimal and I think a slightly higher value will get it just right.

[Electric Warrior]

headphones? you'd better use an amp.

[tjmicsak]

I think .02uf is perfect. I wouldn't go any higher but at least now it makes enough difference to have there.