A problem with germanium transistors is their tendency to degrade over time until they either start leaking too much current also when unbiased or go directly t

A problem with germanium transistors is their tendency to degrade over time until they either start leaking too much current also when unbiased or go directly to short circuit, no matter if they're used or not, so it's advisable to test a small stock before buying bigger lots that could contain many now defective parts. Speaking from experience as I had to ditch like 25% of a big lot purchased years ago in which many were shorted to death. About the AC128, I stopped using it in pedals years ago. It was an ordinary low cost part that later became famous for being used in the original fuzz pedal; as a result it is today sold at outrageous prices, while any normal Ge transistor would work with no difference in sound. It's not the part number, it's the technology: Ge transistors are slower (as in narrower bandwidth) and their sound is therefore less harsh, warmer than Si ones. A pair of ultra cheap ACY* SFT* or many russian ones (less prone to leaks due both to higher [military] standards and their relatively shorter age as the soviets kept producing them long after the west stopped) would sound equally great once the circuit is being adjusted for bias and gain.