What happens if you heat up a Germanium fuzz pedal?

Room temperature at 330HZ high E on guitar

Getting hot at 330HZ high E on guitar

Getting hotter at 330HZ high E on guitar

Way too hot at 330HZ high E on guitar

Increase leakage current: Heat on Germanium transistors will increase leakage current, which significantly shifts the circuit's bias points. Shown on the oscilloscope, the entire waveform shifts vertically relative to the ground, the signal becoming more asymmetrical or 'off-center'.

Asymmetrical Clipping and "Sagging": A Fuzz pedal naturally has asymmetrical clipping, but the bias shift from heat can make it more pronounced, making one half of the input sine wave clipped more heavily than the other. The waveform will appear compressed or "sag" on one side, affecting the symmetry of the distorted signal.

Reduced Output/Sputtering: When the bias point shifts too far due to heat, the transistors no longer operate in their optimal range, leading to a reduction in overall output volume. You can see this happen by turning the bias knob on a pedal, the volume decreases. If the bias drifts enough to push the transistor into saturation the output signal flattens out completely and appear heavily "gated." The signal on the oscilloscope will look "sputtery" or cut out at the peaks of the waveform, especially under heavier playing or with high input signals.

Increased Noise/Hiss: The high gain nature of a Fuzz pedal, combined with potentially increased leakage current in a hot Germanium transistor, can result in an increase in background hiss or general noise on the oscilloscope trace.

Less "Warmth" or More "Farty" Tone: The optimal "warm" and "smooth" sound of a Germanium fuzz is often achieved at a specific bias point (around -4.5V on the collector of Q2). When the transistor gets hot and the bias point shifts away from this ideal, the sound, and thus the waveform's shape on the oscilloscope, can become less desirable, often described as "farty" or "dying"

In essence, the clean, smooth, distorted sine wave (when a sine wave is used for testing) would become unstable, asymmetrical, potentially quieter, and generally more distorted in an undesirable, inconsistent manner, reflecting the well-known temperature sensitivity of germanium fuzz pedals.

The FreezeZone pedal has eliminated the shortcomings of the germanium transistor, by introducing a refrigeration unit inside the pedal.

The video shows the germanium transistor at room temperature with the current gain at 183, the leakage current at 851 milliamps. At 120° Fahrenheit current gain is 28, leakage current is 1,569 milliamps. With the germanium transistor cooled down the current gain is 159, and the leakage current is 38 milliamps.