Best Hfe for a Circuit

[DeadAirMD]

How do you determine the optimal hfe for a circuit? I have a ton of different transistors and I'm always going through them testing them on different pedals I've built from PPCB, but I never know what values I'm actually supposed to be shooting for.

 

[PedalBuilder]

How do you determine the optimal hfe for a circuit? I have a ton of different transistors and I'm always going through them testing them on different pedals I've built from PPCB, but I never know what values I'm actually supposed to be shooting for.

Start by using Google (or the search engine of your choice) to search the circuit name and "hFE." This forum, freestompboxes, diystompboxes, r/diypedals, and the comments sections of effect layout blogs usually have some helpful suggestions. That said, I've found that the common wisdom regarding hFE is not always the sound that I like the most. For example, my favorite Tone Bender Mk. II uses transistors with the following hFE values: Q1 - 55, Q2 - 389, Q3 481. And I have another fantastic sounding Mk. II with hFE values of 83, 29, and 102, respectively, all with leakage >700µA. Again, nowhere close to the usual spec, but it sounds really good. So definitely use your ears and don't be afraid to trust them over the numbers on your tester.

 

[Cybercow]

IMO: It depends entirely on the circuit. For some circuits , the Hfe has little to no bearing. For others, Like TB, RM, FF, Burns Buzzaround Fuzz, and a few others, the Hfe values are critical to achieving an optimal balance across the circuit for performance.