BC108 = BC548 Fuzz Face (with demo video)

[shredgd]

Hi,

this is just to share a short demo I made to show how the BC548 transistor is really just the plastic case equivalent of the metal can "mojo" BC108. I admit it, only recently I read the history of the BC54x family of transistors, and learned they are the direct substitutes of the BC10x family. So I bought some BC548A and BC548B and gave them a try in my silicon fuzz faces.

Q1 and Q2 were a BC108A (hFE 160) and a BC108B (hFE 340) for the first half of the clip, then a BC548A (hFE 150) and a BC548B (hFE 335). Bias was the standard V1/2 for Q2 collector in both cases.
The circuit is a silicon Fuzz Face with the Fulltone '70 mods (10p cap between Q2 base and collector, 0.1 uF output cap).

So, to achieve a nice fuzz tone, there is no need to sort rare or pricy transistors: just buy new production BC548s, which are thankfully sorted for gain (A, B... I wouldn't choose the very high gain Cs), pick an A for Q1 and a B for Q2, just minding Q2 gain is about the double of Q1, set Q2 collector to V1/2, keep the fuzz pot at 9.5 (just back it a few degrees from max) and you're good to go!

Giulio