Germanium Transistor Reviews

[JaviCAP]

Hi mates,

As lately i've been purchasing a lot of different germanium transistors, I'd like to write a brief review of my impresions about the  brands and models I've been tryin'.

First of all: If you just need a low to zero leakage pnp germanium trannies with a hfe from 50 to 120, there's no doubt: russian GT308. You'll get very few over 100hfe, most of them are 50-80. They're absolutely great for Fuzz Faces and Tonbender  MKIII.

Other germaniums that I've tried and would like to comment:

PNP:

AC128 (Tunsgram): Very inconsistent and high leakage (200 to 500 are usual measures) Gain goes from 60 to 140. Many of the are over 100hfe. They sound quite well in many effects

AC188 (Tunsgram): Hi gain germaniums. Very high leakage, very few are under 300, and many ones are between 500 and 800 Only 2 of the last 30 pieces batch I purchased are under 100hfe, the rest goes between 100 and 220.

OC71n: Very low, close to 0 leakage. Very low  hfe from  35 to 60. Pretty useless, except in a Tonebender MKIII, as Q1 and Q2.

2SB187 (Sanyo): A real discovery. Pretty consistent. Moderate leakage (250 to 350) and very high hfe, from 160 to 250

NKT275 (Newmarket): Really shocking trannies. Have never listened better sound in a Fuzz Face. Extremely scarce and expensive. Gain from 50 to 180hfe and low leakages, 50 to 180.

NPN:

OC139: Close to zero leakage, hfe from 20 to 40. Useless (and expensive)

2N1304 (Philips): Moderate leakage <200 and hfe of about 40-50. Pretty useless for most situations.

Still haven't found a decent NPN germanium, of about 100hfe, maybe some day.....

Hope this info is of help for anyone.

[Silver Blues]

Nice one, Javi. I was just thinking, you could use the low-gain "useless" ones in Darlington pairs. Those OC71N have the potential to make a 3600 hfe Darlington, and with low leakage... Or the OC139s at 400...

[IvIark]

Yes that pretty much ties in with my feelings about the ones you listed that I've also tried.  I have some reasonable AC128, but pretty much every AC188 I've ever tried has been utter shit.  OC71's no leakage (or gain) , NKT275s nice and GT308s great but rarely higher than 90 hfe.  One that may interest you is the AC125Kz which I got 150 from eBay at a pretty reasonable price.  Gain was listed at 75 to 150hfe and that ties in very well with the selection that I've measure.  Low leakage and sound pretty good to me.  I think I got them from minifux1.  I also got 100 x 2N404 from the same seller I think and they're great.  The other Russian GT*** trannies are always worth a try for not a lot of cash.

For NPN still the only transistor that I would ever recommend is the MP38A.  Similar to the GT308 is terms of gain, but the only consistent low leakage transistor I have ever found available in quantity.  AC187s were shockingly bad in terms of leakage, I got a batch of 10 and the best was 0.6mA, the worst 1.2mA,

[rocket88]

great write up javi. recently I've been purchasing and using a few different russian ge transistors with mixed results. Here's a list of the ones I've purchased and rough average hfe:

PNP
gt108g - tested between 140-200hfe, most in 150-160hfe rang
gt308b -most tested between 80-120hfe
gt402v - tested between 50-80hfe
it308v (military spec gt308v) - tested between 50-110hfe, most in 80's
mp20a - most tested between 40-150hfe, most in the 70's
mp41- tested between 40-60hfe, most in the 50's
mp41a - tested between 40-80hfe, most in high 60's-mid 80's
mp39b - most tested between 40-60

NPN
mp35 - tested between 40-60hfe
mp38a - tested between 60-110hfe

I've only used the mp38s's and the mp41a's, and had great results. The Russians seem to be super consistent with 0 to very low leakage. Sound wise, I find them to be a little on the darker side, and a little more "growly" compared to similar European transistors. I also find it interesting that even the low gain transistors sound great, when substituted for higher gain transistors, well at least in the pedals I've used them in.

Hopefully I finally help and contributed instead of just asking questions and getting help.

[Dave]

Yeah, very useful thanks Javi, I've not done much experimenting with germanium transistors mainly due to the expense, but maybe I'll track down a few of those.
Cheers
Dave

[rocket88]

Glad to help. I know what you mean Dave. What I did for all the russians was order a few different ones from the same person on eBay and combined the shipping. Some of the ones I bought cost like $7 for 25, others were like $30 for 50, but each shipping was $8. Once it was all combined the shipping went from $120 down to like $40 so it was totally worth it. Just order enough to make the shipping worthwhile.

I didn't put anything up about the ones I've purchased from smallbear as they are exactly as they say they are.

[JaviCAP]

Yeah, minifux is a great source for germaniums and the prices use not to get very expensive on auctions. I've ordered 10 AC125 from him as I wanted to try this model.

AC188 is great for some positions in circuits like the MKI - Zonk Machine, or Q2 on Tonebender MKII when you need to get very high leakage, but these are the only circuits where I've found an use for them.

The 2SB187 are just incredible for Rangemasters or even for Q3 on Tonebenders / Q2 on high gain fuzz faces.

I forgot to mention the chinese 3AX, really cheap, medium leakage and hfe from 60 to 200,  even Steve from Small Bear sells these trannies.

Still have not found a single MP38A over 90hfe, and that's a pity because they're very consistent  being both NPN and germanium made. Anyway, they're the only ones I use when  I need a NPN. Will try some OC141, that are supposedly the high gain version of the OC139, and if about 110hfe should be great for pedals like the Drag'n'Fly.

NOw I have a good stock of about 450 germaniums, so, apart from the OC141 that I want to get and the AC125's that I ordered on past weekend, I think that will get no more in a long time :P

BR

[rocket88]

Javi,
I'm surprised you didn't get any MP38a's over 90hfe, I have a bunch, and a few in the low 100's. Maybe its because I accidentally bought an extra 50, so I have a large stock to pull from. I think I have something like 400-500 Russian Ge Transistors stocked up at this point. I gonna have to pick up some of the ones you've had good luck with. I've been trying to find some OC76's & OC75's, but everyone wants an arm and a leg for them.

[JaviCAP]

Bad luck, I'm afraid... I just purchased a lot of 50 pcs and sometimes I wonder if this bunch was cherry picked previously, as the higher hfe one that I got was 92, and most of them were about 60.

Something similar happened with a lot of 50 1T308, all really consistent, from 70-80hfe every single one :P

Try de 2BS187, they're amazing and cheap, about 35 cents / piece, you'll love them!

[rocket88]

If I may ask, who did you get them from?

[JaviCAP]

Sure, Minifux from Germany (eBay).

Sadly. most of his auctions are for bidding, so you have to wait a week (he uses to end'em up on Sunday) and be lucky to get a nice price. If something gets too high, he uses to send more lots on next week.

BR

[rocket88]

Hmmm. I got mine direct from Russia. I know that some former ussr countries sell them too. You might have better luck with them from the source. I figure who better to get old ussr transistors direct from where they were made and used the most. I'm still trying to track down certain ones.

[JaviCAP]

By the way, I didn't remember that OC139, 140 and 141 (not sure if it's posible to do this with any other model) can be "reversed" using collector as emitter and emitter as colector.

So, in "reverse" mode,  6 of my OC139 read ~125 hfe! I've tried'em in a Drag'n'Fly and they rock! Will have to get some more!