A quick test, with a 2N2222 (not a bad choice for the first transistor in a Tonebender), showed that with sensible choices for the resistors, the collector voltage started to move at about 110 C.RnFR wrote:apparently the first stage has to have temperature compensation. he still won't tell me at what temperature this becomes necessary, though.
Unless you're gigging on Venus, or boiling your gear in salt water as you play, there's little chance of attaining this kind of temperature in normal use.
Back in the days when I used to design amplifiers for accelerometers that had to work in paper mills at well over 100 C, I used to design silicon circuits with temperature compensation. I also design temperature compensation into my RF oscillator circuits. However, for audio frequencies, and at the normal human range of temperatures, any kind of compensation in a Tonebender is just plain stupid.