UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Craig Sawyers · 17th Sep 2017, 12:33 pm

The only *really* important factor is the beta of the transistors, and the original circuits worked "best" - however that is defined for a circuit whose whole purpose is the distort - for beta between about 70 and about 110.

The secondary factor is fT, which ranges from about 1MHz to 5MHz. That may seem well outside the audio range, but since hard fuzz involves driving the transistors from hard off to saturation the lousy slew rate of germanium, which is linked to fT, makes for a softer edge to the sound.

But there are silicon transistors available with the same sort of characteristics. Just as an example the 2N1480 in a TO5 package, which has an hfe of typically 20-60 and an fT of 1.5MHz and a switching time of 25us. Current production at a not so cheap £2.83 from Mouser. But without all the grief to do with germanium leakage.

17th Sep 2017, 12:33 pm	#30
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,977	Re: Transistors for Fuzz Pedals. The only really important factor is the beta of the transistors, and the original circuits worked "best" - however that is defined for a circuit whose whole purpose is the distort - for beta between about 70 and about 110. The secondary factor is fT, which ranges from about 1MHz to 5MHz. That may seem well outside the audio range, but since hard fuzz involves driving the transistors from hard off to saturation the lousy slew rate of germanium, which is linked to fT, makes for a softer edge to the sound. But there are silicon transistors available with the same sort of characteristics. Just as an example the 2N1480 in a TO5 package, which has an hfe of typically 20-60 and an fT of 1.5MHz and a switching time of 25us. Current production at a not so cheap £2.83 from Mouser. But without all the grief to do with germanium leakage.