FUZZ FACE VARIANT SCHEMATIC, INCLUDING MK1.5 & VOX TONE BENDERS
The schematic includes room for components not present on a standard fuzz face, as some variants have additions.
I thought I'd keep it relatively simple and not venture into circuits with input blends or the various trimmers substituted for resistors (at least for now anyway). R1 & R3 are where trimmers are often placed - usually more frequently as R3, sometimes in combination with a low-value resistor. R4 can also be fun to play with, to help fine-tune the circuit.
No attempt has been made to list every transistor ever used in a fuzz face.
FUZZ FACE VARIANT COMPONENT TABLE
TRANSISTORS
Of course, you can't mention fuzz face without talking about transistors. It's definitely a matter of taste - some folks like high-gain silicon, others will settle for nothing but NKT275.
A lot of info out there on forums etc talks about the "best" hfe combination - just ignore that and trust your ears.
NKT275
"The sound of these original NKT275 transistors was quite similar to the other types of germanium transistors that we use. But the NKT275s have less fuzz, and less high end fizziness. They have a deeper tone and clean up better than most transistors. If you turn down the volume on your guitar, the NKT275 sound will be totally, sparkly clean without any fuzz remnants. Normally, NKT275 transistors are not high gain, that is why they clean up so well and are so smooth sounding."
AC128
They did appear in some reissued fuzz faces at one stage, but most experts out there are yet to see one in a proper vintage fuzz face. The general advice is to avoid the AC128. I did make a stellar sounding fuzz face using AC125 once, so the AC series can't be all bad.
VOLATGE
As for the magic Fuzz Face number of -4.5v on the collector of Q2 - it's a good start, but don't stress about it. I tested a really nice Fuzz Face from the first year of production measuring -5v (NKT275 transistors). It sounded great.
If you're making a MK1.5 using OC75s - it's going to be a higher voltage, due to the much higher leakage. Don't bother trying to get it to -4.5v.
VOLUME MOD
A common complaint is that the volume too low.
R2 & R3, usually 470 and 8k2, form a voltage divider from the collector of Q2 to DC supply. AC isn't fussy about where ground is - this means that you have a hardwired volume control before the actual volume pot, which is reducing the output level by a massive amount.
8,200 + 470 = 8,670. So just adjust the resistor values to add up to around the same amount. The most common thing to do is change the 470 to a 1k resistor.
Replacing the 8k2 with a trimmer is also another solution - this often changes the bias. You might like the output level, but then find you prefer the fuzz sound when the level is lower. Anyways, whatever works right...
THE ANALYSIS OF, AND THE DARK ARTS OF THE FUZZ FACE
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