# Recommend some NPN Ge transistors



## DAJE (Dec 31, 2021)

I'm looking at the Aft Preamp (EQD Bows, NPN Rangemaster). So, not high-gain. Low-medium. 

I'm in Australia so former Soviet / Eastern Bloc states are my best option for affordability. Don't want a lot but 10 or 20 would be OK.


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## peccary (Dec 31, 2021)

I have had good luck with MP38A's. I've used them in multiple Dizzy Tones with great success. I have an Aft I can try them in tomorrow if you'd like.

I bought a bag of 20 a while back and here you can see the gain and leakage spread: https://photos.app.goo.gl/p7irixpTFCha6Uf27

Edit to add: leakage isn't on there, my bad. They were all under .300mA


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## DAJE (Dec 31, 2021)

peccary said:


> I have had good luck with MP38A's. I've used them in multiple Dizzy Tones with great success. I have an Aft I can try them in tomorrow if you'd like.
> 
> I bought a bag of 20 a while back and here you can see the gain and leakage spread: https://photos.app.goo.gl/p7irixpTFCha6Uf27


Thanks, that's exactly the sort of info I was hoping for.


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## flemming (Dec 31, 2021)

DAJE said:


> Thanks, that's exactly the sort of info I was hoping for.



I picked up some MP38As recently as well.






						My eBay GE transistor experience
					

This isn't necessarily an endorsement, just sharing my experience.  I picked up a some MP38A and P28 transistors from this ebay seller:  https://www.ebay.com/usr/alexer1  https://www.ebay.com/itm/192849585657 https://www.ebay.com/itm/202649761724  I grabbed 20 of each (The listing quantities...




					forum.pedalpcb.com
				




Robert


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## HamishR (Dec 31, 2021)

I bought some MP38s from Omsk a year or two back. Very affordable and I still have plenty. I googled the address (using google to decipher the cyrillic writing) and found the rather bleak looking apartment block of the seller. Fascinating! It took a while for them to arrive in Australia but they did, and shipping was laughably cheap.

I've had excellent results with Russian Ge transistors. Much better than with the duds you get from western Europe these days.


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## DAJE (Dec 31, 2021)

HamishR said:


> I bought some MP38s from Omsk a year or two back. Very affordable and I still have plenty. I googled the address (using google to decipher the cyrillic writing) and found the rather bleak looking apartment block of the seller. Fascinating! It took a while for them to arrive in Australia but they did, and shipping was laughably cheap.
> 
> I've had excellent results with Russian Ge transistors. Much better than with the duds you get from western Europe these days.



I have a lot of PNP Ge transistors from the former Eastern Bloc, and out of maybe 75-80, two duds. And yes, postage to Australia is much more reasonable, and not that much slower. 

Off topic: I use Google Maps to check out faraway places all the time. If I read a book set somewhere on Earth, I have a look. I look up a lot of music-related places, too. Most recently, I had a look at the Beatles' early homes, and their relation to each other and Strawberry Field and Penny Lane. Plus the Liverpool venues that they played at, some of which buildings still exist. Fascinating to me, and to see that such a group of immense talents all grew up within a few km of each other. I may never make it to Liverpool, but I can have a bit of a look.


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## Chuck D. Bones (Jan 1, 2022)

MP38A and P28 find their way onto a lotta boards I build.  I also have a stash of 2N1308 and 2N1309.  The MP38As tend to be leaky, which can be a good thing or a bad thing depending on the pedal.  In any case, plan on testing and auditioning the Ge transistors because some will sound better than others, again depending on the specific pedal.  To get Ge transistors to bias correctly, it is common to cherry-pick them or fiddle the bias resistors.

And yes, I have driven past some of your homes using Google Street View.  Don't judge me.


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## jeffwhitfield (Jan 1, 2022)

I recently acquired a batch of GT402B’s (near equivalent to AC132) and MP20A’s. The MP20A’s are good for lower gain hFE (around 70-90) with the GT402B’s at higher gains (120-140). Leakage is good and they sound great in a Fuzz Face circuit.


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## jeffwhitfield (Jan 1, 2022)

Chuck D. Bones said:


> And yes, I have driven past some of your homes using Google Street View.  Don't judge me.


Stop by sometime. I make a good cup of coffee. 😁


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## djmiyta (Jan 1, 2022)

I have heard and read about Russian made trannys they’re much better quality for a fair price IF you know where to go , bringing me right to my question can you recommend a place to go to for like surplus Russian stuff?


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## HamishR (Jan 1, 2022)

Chuck D. Bones said:


> MP38A and P28 find their way onto a lotta boards I build.  I also have a stash of 2N1308 and 2N1309.  The MP38As tend to be leaky, which can be a good thing or a bad thing depending on the pedal.  In any case, plan on testing and auditioning the Ge transistors because some will sound better than others, again depending on the specific pedal.  To get Ge transistors to bias correctly, it is common to cherry-pick them or fiddle the bias resistors.
> 
> And yes, I have driven past some of your homes using Google Street View.  Don't judge me.


I have a stash of 2N1308s too, and they can work ok. They might be slightly brighter sounding than the Russian ones, but there's not much in it. IME they are a little fussier about bias than the Russian ones.

In my Simulcast build I used MP20s because that calls for a PNP transistor. I tried a few and they all worked fine regardless of hfe. The western transistors I tried (Can't remember the number - they looked like 2N1308s but were PNP) all needed more work in the biasing before I could even see how they sounded. So I just went with the MP20.

And I love Google street view!


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## DAJE (Jan 1, 2022)

djmiyta said:


> I have heard and read about Russian made trannys they’re much better quality for a fair price IF you know where to go , bringing me right to my question can you recommend a place to go to for like surplus Russian stuff?


Here are a few East Bloc eBay sellers that I've had good results from. 






						sp9tnm on eBay
					

Follow sp9tnm on eBay. Buying, Selling, Collecting on eBay has never been more exciting!



					www.ebay.com
				








						Security Measure
					






					www.ebay.com
				








						Security Measure
					






					www.ebay.com


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## djmiyta (Jan 1, 2022)

DAJE said:


> Here are a few East Bloc eBay sellers that I've had good results from.
> 
> 
> 
> ...


Thank you very much


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## DAJE (Jan 7, 2022)

I ended up ordering some MP38As from this seller in Omsk:








						solovandy | eBay Stores
					





					www.ebay.com
				



I haven't bought from him before but I've seen him recommended on forums and his store is full of Soviet-era goodies. 

I also bought an Aft and a couple of other PCBs because sale. Yay!


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## fig (Jan 7, 2022)

I think I saw you go by the house the other day @Chuck D. Bones !
Is this you?


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## jeffwhitfield (Jan 7, 2022)

fig said:


> I think I saw you go by the house the other day @Chuck D. Bones !
> Is this you?


No, that was his mom.


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## bowanderror (Jan 7, 2022)

There are a lot of good sourcing suggestions here, but the actual part number doesn't matter as much as the individual gain (hfe) and leakage (Iceo on some testers) values, which vary a lot even between the same part# & lot.

A good rule of thumb is to look for hfe greater than 50 and leakage below 200uA. Some builds will require higher hfe values, so you may want to look into spending more on pre-tested transistors if you need a certain range.


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## peccary (Jan 7, 2022)

DAJE said:


> I ended up ordering some MP38As from this seller in Omsk:
> 
> 
> 
> ...


I think that may be who I got my MP38A's from as well.


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## MobyOctopad (Jan 7, 2022)

bowanderror said:


> There are a lot of good sourcing suggestions here, but the actual part number doesn't matter as much as the individual gain (hfe) and leakage (Iceo on some testers) values, which vary a lot even between the same part# & lot.
> 
> A good rule of thumb is to look for hfe greater than 50 and leakage below 200uA. Some builds will require higher hfe values, so you may want to look into spending more on pre-tested transistors if you need a certain range.



When I was reading through RG Keen's write-up on the Fuzz Face, I thought I remember reading leakage up to 300ua would work in a FF. Is that not the case?


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## bowanderror (Jan 7, 2022)

That's just a general range, but different circuits will play better/sound different with different values, and the Fuzz Face is fine with higher leakage transistors.


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## Chuck D. Bones (Jan 8, 2022)

bowanderror said:


> That's just a general range, but different circuits will play better/sound different with different values, and the Fuzz Face is fine with higher leakage transistors.


The FF will tolerate a leakage up to a point.  Too much leakage in Q1 will screw up the bias point.  Germanium transistors should be auditioned in every circuit because: a) it can be difficult to predict how they will behave many circuits; b) what sounds "good" is very subjective.


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## DAJE (Feb 10, 2022)

Got my bag of Soviet-era MP38As today. Did a quick test and all but one are between 60-110 hFE. The outlier tested at 40, but that's still potentially useful. They seem slightly leakier than your usual USSR trannies, which is also cool.

The other numbers have to be month/year, which means they're all from the mid 70s, coming up on 50 years old. Genuine vintage.


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## Chuck D. Bones (Feb 11, 2022)

Watcha gonna build?  Not too late to enter something in the Muffin contest.


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## DAJE (Feb 11, 2022)

Chuck D. Bones said:


> Watcha gonna build?  Not too late to enter something in the Muffin contest.


AFT Preamp AKA EQD Bows AKA a Rangemaster with NPN tranny. I have a PNP Rangemaster I built a while ago but the simplicity of the Aft is attractive. I grabbed a few of the simplest PCBs last time I shopped from here. I only need one transistor for that so I'm pretty sure to be looking out for uses for the rest of them.

I'm still at the learning-what-the-things-do phase, designing something myself is a bit too advanced for me. Great concept, though, I've been observing the Muffin contest progress.


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## Chuck D. Bones (Feb 11, 2022)

Don't be surprised if the AFT / Bows bias drifts all over the place.  R5 is way too small, should be at least 1K.  It's 3.9K to 4.7K on the Rangemaster.


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## DAJE (Feb 11, 2022)

Chuck D. Bones said:


> Don't be surprised if the AFT / Bows bias drifts all over the place.  R5 is way too small, should be at least 1K.  It's 3.9K to 4.7K on the Rangemaster.


I socketed the bias resistor on the Aion one I built last year, and I'm glad I did because I had to try a series of them to get it to bias. Thanks for the tip, I'll socket that one too. I've used a few of your tips in builds already, and haven't regretted it.


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## Chuck D. Bones (Feb 11, 2022)

If it was my build, I'd install 2.2K for R5 and tweak R4 to get Q1-C around 5V to 5.5V.  The bias will be stable and you'll have plenty of headroom.


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## DAJE (Feb 11, 2022)

Chuck D. Bones said:


> If it was my build, I'd install 2.2K for R5 and tweak R4 to get Q1-C around 5V to 5.5V.  The bias will be stable and you'll have plenty of headroom.


Noted. I have another couple of pedals in the queue before the Aft, but I will save your advice and apply it. Thank you.


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