Germanium help

[Synsound]

An old buddy just gave me some germaniums but I'm unsure where these can be used. He states the are Russial military spec low gain PNPs. I'm getting a hfe measurement of around 24. My tester is not the best. Anything anyone knows would be great. I've never worked with germanium. I would like to do fuzz factory but I'm not sure these will do. If not what would be a good home for them?

[Synsound]

One more pic

[induction]

When you measure Ge transistors, you have to account for leakage. I use RG's method. Leakage makes the gain look higher than it is, so if you didn't account for it, the hfe may be even lower.

The 'ideal' hfe range for a Fuzz Factory is the same as for a Fuzz Face (roughly 80 to 120), so if you're a traditionalist, 24 is way too low. But some people have reported good results with low hfe transistors in a Fuzz Face, though I don't know how well this will translate to a Fuzz Factory. Can't hurt to breadboard it.

If all else fails, you can use them as Ge diodes.

[Beaker]

MP25 PNP military (you can tell by the rhombus printed on the top) germanium - nice! How many do you have?

Not sure if they will work in a Fuzz Factory, but you know the rules Synsound - socket and see.

Rather than have a specific build in mind for these transistors, I find it's better to build a pedal, and experiment with transistors like this, just to see what happens. some will sound bad, some will sound great.

Try a PNP Germanium Giant for a start.

HFE 25 sounds at the low end of the gain range for these, they should be around 50 (I think), but you should find plenty of uses for these.

[Frank_NH]

How about using them in a Darlington configuration?

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

[Beaker]

That would work.

[Synsound]

Thanks for the responses guys! I will tinker around when I get the time.

[Neil mcNasty]

It is important to notice that many Russian Germanium transistors (like these MP25's) often perform very well, even when the hfe is "way too low".
Socket and try, is the way to go!
Either the transistor sounds good, or it sounds a bit... Naaaaah...
It would not be surprise me if they actually sounds good in a Fuzz Factory, and I doubt that Mr.Wex has been buying top shelf AC128's for this pedal design.
More likely they are quite average and leaky...

Russian Germanium transistors tend to be more consistent regarding leakage (almost zero, so they are perfect for Darlington Configuration) ...and most of the time, a 50 hfe Russian will out-perform a European/American 100 hfe transistor in a circuit, which often is very in-consistent and leaky, because of the fact that the supply has been drained, leaving mostly the "duds" for the pedal geeks that believe in mojo part numbers.

When I'm dealing with the MP series transistors. I actually never measure them...
I just pick a random one... slap it in... and it always sounds pretty good, as long as you make sure that the bias resistor is swapped with a trimpot, so that you can dial it in at the sweet spot (as you'll always have to do with Germaniums...)

What I'm trying to say is...: Do not apply the standard "Germanium Knowledge" when dealing with Russian Germaniums!
They work better than you would expect from any other Germanium transistor.
A 25 hfe Russian, often performs just as good as a European 60 hfe with minimum leakage...
Remember that these are Military stock transistors with minimum leakage, from the top shelf of it's time, and It's not the crap low shelf AC128's you get at ebay these days...

My best tip would be to socket every transistor, regardless of circuit, and try to put one of these MP25's in every pedal you have built, that has a socket. You'll be surprised by what you learn and discover...
The Germanium Giant is a perfect example of this!
A simple Elektra Distortion aka Green Giant (in this case), becomes one of the sweetest sounding circuits EVER out there! (BUILD IT!)
And this happened just because someone from this forum tried a MP38 Germanium in it, instead of the silicon that the original circuit asks for...
In other words: HE DID SOMETHING WRONG!
So: DO SOMETHING WRONG WITH IT!

[Beaker]

As the guy who "DID SOMETHING WRONG" in Neil's words, I just looked at the Green Giant when it was first posted up. I thought to myself "cool pedal, but I don't have any of those transistors".

Then I thought "Hang on, I've just got a load of MP38s in from Bulgaria, what would happen if I converted the pedal to NPN, and tried one of those?"

That was the sum of my logic when doing this. i was expecting it to "work" (as in pass some kind of signal), but I never expected to work anything like as well as it does.

So yes, just try your MP25s in different circuits and see what happens. It's just taking that step from "paint-by-numbers" pedal building to actually creating something new.

[Synsound]

Thanks again guys. I guess my lack of knowledge had made me gun shy. I will start sticking them in any hole I can find. How could thAt go wrong in any situation?

[Muadzin]

I never thought I'd hear the words quality and Soviet era production in the same sentence.

[rocket88]

Bwahaha. I don't know if it's really quality. I think the reason they're more reliable is that since the soviets didn't switch to Si they developed better methods for making Ge transistors, mostly because they had to.