Chuck D. Bones
Circuit Wizard
Is there a way to make use of low-gain Germanium transistors? Can we build a Darlington pair from Ge transistors? These are good questions and pedal designers have been dealing with the problem of low HFE transistors from almost day one. If you want to see an example, you need look no farther than the Tone Bender Mk III and Burns Buzzaround. Refer to the PedalPCB Gnat schematic. Q1 & Q2 form a Darlington pair. Leakage multiplies the same way that HFE does in a Darlington pair, which is why the designers put R4 there.
So there's the answer. But as they say on TV: "Wait, there's more!"
Q2 does most of the heavy lifting re: distortion, so we could make Q1 silicon and get pretty much the same tone. Now leakage is less of a problem and we can get rid of R4.
Another alternative is to build a Sziklai pair and make both trannies Ge or construct a hybrid circuit where one of the transistors is silicon or a JFET. The only hard part, and it really isn't that hard, is sizing the resistors.
So there's the answer. But as they say on TV: "Wait, there's more!"
Q2 does most of the heavy lifting re: distortion, so we could make Q1 silicon and get pretty much the same tone. Now leakage is less of a problem and we can get rid of R4.
Another alternative is to build a Sziklai pair and make both trannies Ge or construct a hybrid circuit where one of the transistors is silicon or a JFET. The only hard part, and it really isn't that hard, is sizing the resistors.