After spending some time on the germanium Fuzzrite, time for a bit of silicon action. It's a bit less interesting, as there seems to be less variance to the circuit - or none?
Some differences in construction methods occurred, but that's about it as far as I can tell. Although I need to do a bit more research on this, as I'd like to see some pot values on an original to confirm what the internet has been saying.
POTS
It seems that most people have settled on 350k for Depth, with was a common value used in Mosrite guitars at the time and also used in the germanium version, so this seems likely.
I've seen a few different values for the Volume pot floating around - anywhere from 33k to 500k. The value of the Volume pot has a direct effect on the frequency response of the pedal.
The differences in values show up the most when the Depth pot is set to Q1 (Depth blends between Q1 & Q2). A smaller volume pot reduces bass in this setting.
THE 22K RESISTOR
There's still conflicting information floating around about the inclusion of the 22k resistor that forms the 3.3khz high-pass filter with the 2n2 capacitor on Q2. Some people like to have it on a switch or change the value to 47k
The chart below used identical settings to the one above - except that the 22k resistor was removed. As you can see, it significantly changes the frequency response and output level.
TRANSISTORS
The original used TZ82, which if you find any will probably cost a lot. The general consensus is that almost any low-gain silicon transistor will provide good results (about 200 hfe and under).
Usually, people report good results with Q1 having a higher hfe than Q2.
Modern subs PN2222A, 2N3903
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