Germanium transistors besides AC128?

[Rick]

Gotta' agree with the previous poster who had good luck with Japanese 2SB series of trannies, I did also. Great FF, Rangemaster and Tonebenders made with these. Haven't had the pleasure of any 2SA ones yet, but the 2SB54, 173, 175, even 32, 33 all worked very well. And again the 20 or so AC128s I procured some time ago were all way too leaky / noisy to be used at all. Hopefully others got better ones than my lot.  I still have a few packs of ten in shrink wrap that I could part with (2SBs that is). oops maybe wrong forum, sorry, or I could just send you my AC128s for the price of pretty much a postage stamp.

[mac]

Sidenote/question: The forward voltage drop on a silicon diode is about .7, whereas on a germanium it's around .2. Can the same assumption be made for Ge and Sil trannies? I was basically assuming that if a transistor is Ge, the fvd between the emitter-base and the collecter-base would be around .2.

Only the emitter-base is around .2v

If you are new to the FF you can download this soft that can guide you:
http://geocities.com/guitarfxs/exes/biascalculator.zip


mac

[yeeshkul]

i have to recommend Macushita 2SB 175 i used in my FF clone  - they leak just a bit and sound great. They seem to be quite temperature-stable as well. Better than AC ... probably.

[mac]

i have to recommend Macushita 2SB 175 i used in my FF clone  - they leak just a bit and sound great. They seem to be quite temperature-stable as well. Better than AC ... probably.

I agree. Matsushitas are solid rock. I have a bunch of 172, 175 and 176 and others and no one is hissy or faulty. Toshibas rocks too and leak less.
I found that less leakage implies less thermal runaway.


mac

[jmusser]

The 2SB Japanese types seem to be pretty good. I have used them to make a few fuzzes  out of. They were in an old plastic radio that was all busted up, but worked otherwise. Don't forget that for the real low hfe and leaky germaniums, that they can be piggy backed such as Pete did in the Range Pig. That's a good sounding fuzz circuit on it's own, and changing bias with trimmers can make it have different tones. I always thought that was one of the brightest ideas to show up on the forum.

[Fuzzy-Train]

Noob questions: What is a "leaky transistor", what are they leaking, and are they good or bad?

[mac]

Leakage is curent flowing from the collector to the emiter through the base. If you connect a NPN Ge tranny with a 1K resistor from collector to +V, emiter to gnd and base unconnected, you'll see a voltage drop across the 1K. 200uA, which is the upper limit for a good FF will make a 0.2V drop.
There is a post here about the 'sound of leakage'.


mac

[Fuzzy-Train]

Thanks... I'll try and look for it.

[Fuzzy-Train]

Here's one I forgot to ask: What causes a transistor to leak? Heat, cold, abuse... or just time?

[Seljer]

Here's one I forgot to ask: What causes a transistor to leak? Heat, cold, abuse... or just time?

I think its just one of those inherent qualities of the p-n junction of semiconductors? they can't manage to block all those electrons from passing in the other direction

[Fuzzy-Train]

I guess that makes it part of the reason why they sound so good?

Thanks for the help, and info.

[mac]

Here's one I forgot to ask: What causes a transistor to leak? Heat, cold, abuse... or just time?

This is a quantum statistical mechanics question. Not sure but I guess that electrons in a germanium transistors -- this is stuff I've not seen in 20 years! -- are less restricted to move than in a silicon one, and posibly they have a bigger chance to pass to the other side. Where the heck is my periodic table?

Also I think good manufacture technics can contribute to the final leakage.

As far as I know I have a lot of Toshibas and Matsushitas that may have more than 30-40yrs and they still fuzz.