Is there an ABC's or FAQ for transistors in regards to fuzz pedal building?

[skiraly017]

I'm about to start building fuzz pedals but do not know the first thing about transistors. Is there something that breaks it all down? Silicon vs. Germanium, how to measure and match, what's desireable and what's garbage. is it safe to buy NOS off Ebay or is there a trusted source. Thanks for the help.

[R.G.]

There is nothing that breaks it all down that I know of.

I'll try to answer whatever you need.

Silicon vs germanium?
Use the one that's in the schematic. They bias quite differently, and changing one for the other can be done but requires knowledge you don't have yet. Some circuits will work fine, some will not, and the differences can be extensive.

How to measure?
Get a multimeter with an HFE setting. I personally just use this as a "transistor is acting like a transistor" test, but it's useful for that.

In most cases measuring is not needed. The vast majority of circuits do not need and will not benefit from matched transistors. There are enough exceptions to make you ask the question, though.

In general, older germanium based circuits will need pre-tested transistors. This is because the old stock germanium devices vary even more wildly than JFETs. Of an honest sample, only about one in three will be useful. Buy them pre-tested until you are ready to bet your own money on how many good ones you'll get. I wrote the first article on testing germaniums. It's at GEO. Read it. It tells you the basics of testing germanium, and why the hfe tester on your multimeter won't get the right answer.

Buying germanium from ebay will generally get you a batch that has been pre-selected - the wrong way. The seller often has found a batch in the back of an old shop and pre-tested all the good ones out, and they're looking to sell off the rejects. That's not universally true, but it does happen. Small Bear Electronics is a trusted source. Otherwise, only bet as much as you can stand to lose.

In general, transistors don't need to be matched. Most circuit designs are designed so that if they just have enough gain, they work OK. The exceptions are
- germaniums in the Fuzz Face and other vintage germanium circuits
- JFETs in phasers (yes, there is a JFET matcher at GEO)
- Some bipolar circuits need matching; this is so rare that I have not written articles on how to do it.

For bipolar (NPN or PNP), just remember Keen's Second Law - When in doubt, us a 2N5088. Well, OK, for a PNP, use a 2N5087. Or 2N3904/3906. Or 2N4124/2N4125...

Whatever devices you get DOWNLOAD THE DATASHEET.

And remember to download the datasheet. The first 80% of beginner's problems are with pinout and connection problems, and the datasheet is a great help.

The other 80% of beginner's problems is soldering 

[RDV]

R.G.'s post here should be in the FAQ, or at least the WIKI.

RDV