Over the years, I’ve been asked “can I swap the silicon transistors in my fuzz with germanium transistors?”. My typical reply is ”sure, but it won’t work”. So let's take a shallow dive into the difference between the two elements so we can understand what makes each unique.
Audio transistors are semiconductors that amplify an audio signal and clip the signal.
Silicon, which is more modern, is highly reliable, temperature stable, more consistent from piece to piece, has a higher gain and rarely any leakage.
Germanium, which is much older, is inconsistent from piece to piece (which requires testing), thermally unstable, and are lower gain and rather leaky.
In terms of how they sound, silicon has a more "hi-fi" sound due to it’s wider frequency response. Germanium has a smaller frequency response giving it a warmer, rounder, more vintage tone. Makes sense, right? If you want tones from the 60’s and 70’s, you’d use the tech that was available at the time.
So why can’t they simply be interchanged in the same circuit? They have different bias voltages, which is the quick answer, but will require a deeper dive
In part two, we'll go further into how to apply each type of transistor in your circuit, things to consider when choosing between the two and how different companies have utilized both over the years.