I was going to try and build a silicon axis face, but I can't find the transistors, so I was wondering, if I build a germanium one, will AC128 transistors do? Also, it says on them to choose between 'High gain, Medium gain and Low gain', what combination of these do I need for the 3 transistors in the axis face germanium?
Banzai should have the silicon transistors for the AFsi. I think BC108c's are a popular choice, though I haven't built an Axis Face Si, only a germanium.
The different gains (low, medium, high) in germanium transistors will change the sound of the pedal slightly. Low will provide a smoother, slightly bluesier sound, medium will be the classic Fuzz Face tone, and high gain transistors will offer a more aggressive, somewhat heavier sound. Choose the transistors based on the sound you want, or if you're not sure, get one pair of each and try them all out once the pedal is done. Just use transistor sockets instead of soldering them straight to the board, and simply pull out one pair and try another. You can keep the extras as replacements or sell them to someone else on the forum in England. Transistor sockets are a good idea when using germanium anyway, as ge transistors are more sensitive to temperature and can be damaged during soldering. Also FYI there are only two transistors in the Axis Face (and most Fuzz Face derivatives) and a reverse biased germanium diode in the Ge version (also available from banzai), so you only need one of banzai's matched pairs, rather than three trans. Enjoy the project, and happy tweaking!
