106NU70 Germanium Transistor Equivalent

greypilgrim76

greypilgrim76

Active member
Hi All,

I made the classic mistake of impulse buying a PCB a while back--in this case the Muffin Factory--and while I'm excited to take on such a complex build, I didn't check the components before pulling the trigger. Now I'm realizing that the 106NU70 germanium NPN transistors are pretty much unobtanium these days, and I'm sort of stuck on what to substitute for them. I've found some NPN germaniums in a few places like Small Bear, but I'm not sure what hits the reuquired sweet spot of 55-65 hfe. I don't have a transistor tester, so I'd prefer to buy something that will likely fit that range, if possible. Or, maybe a place that sells them with verified hfe ranges. Any suggestions on where to find this last piece of the puzzle?

Many thanks!
 
Sovcom on ebay seems to be the place to buy germaniums. My order is supposed to show up soon and I ordered from them because other people mentioned it in some threads on here. They aren't measured so buy extra so you can test them, and since you gotta buy extra it's worth importing anyway cuz they are so much cheaper.
I ordered mp38a's to use but have not used/tested them yet since I'm still waiting. Hopefully someone will be in here suggesting some specific ones they have used for you soon
 
It’s not FF or TB where people usually aim for certain gain and leak. IMO everything between 20-90 hfe is mostly fine. Also the feedback circuit from C to B helps clipping stages transistor biasing. And if not, fine tune E or C resistor values.
 
So as I was poking around online, I came across these at Small Bear:

smallbear-electronics.mybigcommerce.com

2N1302 Germanium Transistor NPN RCA

New England's source for guitar pedals, pedal parts and electronics.
smallbear-electronics.mybigcommerce.com smallbear-electronics.mybigcommerce.com

If I got one in the 51-60 Hfe range and another in the 61-70 range, would these be reasonable substitutes? The internet tells me their leakage is usually passable for this sort of circuit. I don't know enough to know what I don't know, though... :)
 
NU70 is listed as 35-70 beta.
the biggest thing you are after is low leakage. From there, adjust E and C resistors as @JohnnyCreepy said, until you are somewhere around 4.5v, give or take a half volt. See kit rae schematics for notes on these resistors.
Edit:
Disregard the comment on base voltage.
According to GGG, Q2 and Q3 should be around:
Q2
Collector 3.8
Base 0.6
Emitter 0.03

Q3 (Q4 in muffin factory)
Collector 3.8
Base 0.6
Emitter 0.03
(Leakage will alter these some, as will E and C resistor changes)

Leakages are listed on the schematic in the build doc as
Q2: 260uA and Q4: 390uA
Most Russian germs will be able to attain that. If you have lower leakage transistors, that's fine. But I would keep it below 500uA, for sure.
A lower beta and lower leakage would be fine as well. Something like a 35-45 hfe and <50uA.
As always, mind/check the pinout. Paint/dot on collector with EBC PINOUT for NU70s. A lot of Russians are CBE I believe.2n130x are EBC.
1779062902506.gif
 
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So I'm not overly familiar with the statistical likelihood of finding good matches for a particular pedal by buying a random lot of transistors off of ebay, but based on some of the comments above, I'm wondering if this would lead to two usable transistors:


I've never bought one of these imported bunches, so I don't know if this would just be throwing money down a well, or two of these would likely fit the bill. Any advice from folks who've done it before?
 
I usually buy in larger quantities such as100 but, in my experience, they're all usable. Just get a CCTT or something that can measure hFE and you're off to the races.

When I built the Muffin Factory I just used the first two MP38A transistors I pulled out of a box and it sounded fine.
 
Update: the Ukrainian tracking says that my MP38A transistors were delivered on Friday by USPS. Just got home from a trip and the package is nowhere to be found. There was lots of mail in the mailbox, but no transistors. Kind of amazing that they could get all the way from Ukraine to my town in Indiana only to be misdelivered. I started a ticket through eBay and will stop by the Post Office tomorrow, but I have a sinking feeling that, since the tracking shows it as delivered, I'm likely SOL unless the seller wants to work with me. Assuming things don't work out, does anyone know anywhere else to get these transistors?

Always fun tracking down Cold War components. Sigh.
 
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greypilgrim76 said:
Update: the Ukrainian tracking says that my MP38A transistors were delivered on Friday by USPS. Just got home from a trip and the package is nowhere to be found. There was lots of mail in the mailbox, but no transistors. Kind of amazing that they could get all the way from Ukraine to my town in Indiana only to be misdelivered. I started a ticket through eBay and will stop by the Post Office tomorrow, but I have a sinking feeling that, since the tracking shows it as delivered, I'm likely SOL unless the seller wants to work with me. Assuming things don't work out, does anyone know anywhere else to get these transistors?

Always fun tracking down Cold War components. Sigh.
Click to expand...
Is the tracking to your address/city?
Sometimes those guys, like Ali, will ship multiple orders to a handler/middleman, to be broken down and split up. My guess is you'll see a shipment from Florida or Jersey in your mailbox in a few days
 
The Ukrainian tracking website shows my address (or at least my city/state) when I enter the tracking. It shows that it was handed off to USPS on Thursday last week and then delivered on Friday. We'll see, I guess...
 
Qh. that likely just means that USPS has it. I don't think they have visability to it after handover and for all intents, the Ukrainian post has delivered it, to USPS. Give it a few more days.
 
Yeah, that's what I'm hoping. Here's what I'm seeing:

Screenshot 2026-06-01 at 7.42.25 AM.png

The last three steps make it look like it arrived at my USPS office, they sent it out for delivery, and then it arrived at my house, but it's just vague enough that I can't know that for sure. The only thing I know for sure is I haven't seen any transistors, so I'll swing by the post office today and see what they can tell me. The seller has been communicative so far, but my read from him is that he's basically going to say "It says it was delivered, so that's your problem." I could be wrong. We'll see, I guess!
 
jwin615 said:
Qh. that likely just means that USPS has it. I don't think they have visability to it after handover and for all intents, the Ukrainian post has delivered it, to USPS. Give it a few more days.
Click to expand...
Turns out you were exactly correct. I stopped and let the Post Office know their delivery notification was wrong, they said they'd look into it, and then it showed up today. All's well that ends well! :)
 
Usually you can put the foreign postal service tracking number into USPS.com tracking and it will show up.
It might not show anything at first, when it’s not in USPS’s system yet. But once the Ukraine Post (or whatever they’re called) site shows it’s left the country, start tracking it via USPS. Should be a bit more accurate.

Recent Sovcom order I made:
IMG_2674.png
 
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So I finally had a chance to sit down and run RG Keen's test on the MP38A transistors. I tried to stay as close to the numbers as I could, though my 9v power was actually 9.19v and my smaller resistor was 2.499k. That seems close enough for government work to me, though.

Anyway, here's how my six transistors shook out:

#1: .13 mA leakage, 62.3 hFE
#2: .15 mA leakage, 60.4 hFE
#3: .15 mA leakage, 65.0 hFE
#4: .25 mA leakage, 71.5 hFE
#5: .10 mA leakage, 48.4 hFE
#6: .19 mA leakage, 82.2 hFE

I'm assuming that any of these would work in a pinch, but are there a couple here that seem particularly appropriate for the Muffin Factory Q2 and/or Q4, or would they all be equally fine?

Also, does anyone have any suggestions for the four transistors I don't use for the Muffin Factory? They all seem to have tested well enough that I feel like I should use them for something. Any PedalPCB builds that are just begging for some NPN germanium? My current fuzz collection is a Double Muffin (Triangle and Civil War), StewMac Sun Fuzz, JHS Bender, JHS Lizard Queen, and EHX Big Muff Op-Amp, along with some distortions/preamps that have some fuzzy settings.

I'd be game for something old school, but really, any way to use the transistors effectively would be cool. Thanks!
 
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JohnnyCreepy said:
I’ve liked this and it has kept place as my main pedal since building it.

View attachment 118245
ASYs I used have really low leakage & hFE range from 45-70.
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Very cool! I don't know this pedal, but a little Google research has me thinking it looks pretty cool. So, if I'm seeing it right, you swap out the first BC338 and the SN5088 for the germaniums, switch the second BC338 to a BC517, and change the cap going into the BC517 from 470n to 68n? Am I missing anything? I noticed the 10k resistor going to ground is underlined in green and an arrow circling back to it, but I'm not sure if that's noting any change or not.
 
greypilgrim76 said:
Very cool! I don't know this pedal, but a little Google research has me thinking it looks pretty cool. So, if I'm seeing it right, you swap out the first BC338 and the SN5088 for the germaniums, switch the second BC338 to a BC517, and change the cap going into the BC517 from 470n to 68n? Am I missing anything? I noticed the 10k resistor going to ground is underlined in green and an arrow circling back to it, but I'm not sure if that's noting any change or not.
Click to expand...
10k is a trimmer wired as variable resistor for biasing. Last transistor is a darlington one with 20k hFE. Cap before it was changed to 680n one, ’cos that was closest value I had at hand back then. And it lead me to use darlington transistor also, other Si ones didn’t work with 680n cap. I’d pick a 220n or 330n for it now and Si transistor with sub 1000 hFE.
 
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