Great Jumpin Germaniums! (Ge Diode and Transistor Reviews & Discussion)

[Sensei Tim]

The answer might be in here but I probably missed it when searching thru this thread.

What are "acceptable" leakage current for germanium transistors?  10s of uA? 100s?

[Emil]

This is what it says on geofex:

"How much leakage is too much? 100uA is common, 200 happens pretty often. More than 300uA means the device is suspicious, and more than 500uA I would say is bad."

Then I guess it depends on the circuit what sounds best.

[Gabi Smith]

Hello, i've just find some NOS trannies OC71 and Something like 30 NOS diode OA73 on the fleamarket.

The hfe of the trannies I have measured are: 84, 48, 63, 65, 89, 52, 73, 72, 71, 55, 68.

Are they good for Something?

[Travis]

That’s a bitchin score! Actually pretty high hfe for those. I’d probably do the Carlsbro Fuzz first since that actually used OC71 originally

[Gabi Smith]

Cool, go for a Carlsbro... About the diodes : Does it make sense to put some Ge diode in "tube screamer like" circuit ? And is there any reason to use an op amp instead of a tranny to boost the sound? (The gain that can give an MPSA13 booster is really loud !)

[Travis]

Of course you could experiment with using those diodes for clipping in a variety of circuits, including the tube screamer. If I were using them in a tube screamer I would most likely arrange them for asymmetrical clipping to reduce the compression and volume loss

You could use a transistor instead and of course many circuits like the Big Muff have done that. The tube screamer was unique in the way it implemented the clipping diodes within the non inverting amplifier stage for a more gradual onset of distortion compared to predecessors like the MXR distortion+. If you change this, you no longer have a tube screamer.

The Big Muff has a cool way of soft clipping with transistors by putting the diodes between the base and collector (using common emitter gain stages). You could experiment with one of those clipping stages for more of an overdrive effect. Not a tube screamer, but that isn’t really important

[Gabi Smith]

 So many things to try !

[GrooveChampion]

Got some PNP SFT306's and Bulgaria and some NPN GT38's NOS from Russia on the way, any ideas what to build with them?

And how do I deal the temprature change issue?

[Gabi Smith]

Hello,

Has someone already tried some AF379 in fuzz circuit? What was the result?

[Strassercaster1]

Hey just a heads up you can get germanium transistors on alibaba . Put in the part number and up to a week later you will get responses . It cost me about 180 bucks for 200 germanium transistors new old stock . Motorola brand NPN . Out of the 200 I would say half were between 50-100 HFE. About 50 were between 70-120 Hfe  great for rangemasters and some
Fuzz pedals. So about $3.50 each for good ones that’s reasonable . Plus I could sell off the lower gain ones on eBay to recoup some of the money and yes I would post the range is between 20-50hfe for buyers to know what they are getting