3AX31C Germanium gain

M

makisushi

Member
I ordered some germanium transistor from AliExpress before I knew eBay was a better source. The gain is all over the place with theses AX31C. I'm currently working on a tone bender and fuzz face pnp. Where should I start in term of gain ? I'm also waiting for more germanium from eBay
 

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I also bought a batch of these and had to trash most of them.

Which Tone Bender? There are at least 4 different circuits.
 
makisushi said:
The tayda one. Waiting for the pump charge inverter.
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Is the Tayda PCB a Tone Bender Mk. I? Mk. 1.5? Mk. II? Mk. III? Each one is a very different circuit. With that said, leakage will matter more than hFE. I’d recommend breadboarding the circuit before building it, especially if it’s not a Tone Bender Mk. III.
 
I don't know which version it is. They are using 3x 2N3904 for the NPN version, so 100 hfe +? . I use socket for the transistors so I can swap them... Does leakage needs to be high or low? do they all need to be around the same values or one pair and one other?

Tone Bender

This is the Tonebender, one of the most iconic fuzz effects from the 60s.
www.taydakits.com
 
here's the recommend value from Tayda but can I really use 3 differents gain with 2 bias?


Q1: β = 70-90
Q2: β = 50-70
Q3: β = 110-130
 
It's the MK2 then. A Fuzz Face with a transistor stage in front.
Those are the gain ranges. You want leakage in Q2 and Q3 above 100uA.
Q3 should be around -8V
 
Might as well share my experience here. I've never built anything Germanium, and I'm not sure I fully trust the DSO-TC4, but I ordered 10 each of 3AX31C and 3BX31C, just to see what sort of parameter spread you might get. Not sure if any of them will be useful for a circuit?

3ax31c.jpg
3ax31c-tester.jpg
3bx31c.jpg
3bx31c-tester.jpg
 
rossbalch said:
Might as well share my experience here. I've never built anything Germanium, and I'm not sure I fully trust the DSO-TC4, but I ordered 10 each of 3AX31C and 3BX31C, just to see what sort of parameter spread you might get. Not sure if any of them will be useful for a circuit?

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The leakage is off the chart for all of them. In line with my experience when I bought a batch of these transistors. Unusable, I would say.

I consider low leakage any value below 100uA. For circuits that require leakage, I would go 100-300uA. Above that usually sounds noisy and overall bad.

Low gain to me is 50-80 hFE. Useful if you have hot pickups, otherwise weak.

If you have a breadboard going there's no harm popping these in to see what happens. Try a Germanium Fuzzrite. It will be gated with that leakage, which is great with single coils.
 
andare said:
The leakage is off the chart for all of them. In line with my experience when I bought a batch of these transistors. Unusable, I would say.

I consider low leakage any value below 100uA. For circuits that require leakage, I would go 100-300uA. Above that usually sounds noisy and overall bad.

Low gain to me is 50-80 hFE. Useful if you have hot pickups, otherwise weak.

If you have a breadboard going there's no harm popping these in to see what happens. Try a Germanium Fuzzrite. It will be gated with that leakage, which is great with single coils.
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I wonder if the Chinese germanium bubble has already burst? Seems no one recently has tested any of worth. I might try them as diodes.

I'm not really a big fuzz guy. More preamp type circuits. Maybe some Darlington pairs could work? But even then I think the leakage is too high?

I bought a box of P416B from our trusty neighbourhood Ukrainian ebay seller. Hopefully there's some useful ones in there.
 
I do need to try the RG keen method too. I don't know how much I trust the TC4. Really useful as a sig gen / oscope but probably not as reliable for transistors.
 
rossbalch said:
I do need to try the RG keen method too. I don't know how much I trust the TC4. Really useful as a sig gen / oscope but probably not as reliable for transistors.
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I use a TC1 tester and it has served me well. The RG Keen method works better if you rig it up but I decided it wasn't worth it for all the junk parts I buy :)
 
I recently bought some 3AX85Cs and 3AX83Cs.

Iceo for all was 1ma and above using the RG keen method.

Most were around the 3ma range. Which is just about as bad as one can get using the RG keen method.

I can't say I've been endeared to Chinese germaniums yet. Sure, they'll be good additions to the stockpile of bad components for making sculptures of stickmen being murdered by giant tripods, but that's about it.


rossbalch said:
I'm not really a big fuzz guy. More preamp type circuits. Maybe some Darlington pairs could work? But even then I think the leakage is too high?
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You'll generally want low leakage, low gain transistors for Darlington pairs. The leakage is multiplied along with the gain.

rossbalch said:
I bought a box of P416B from our trusty neighbourhood Ukrainian ebay seller. Hopefully there's some useful ones in there.
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P416B or b? Russian transistors are tricky. Their "B" looks like a lower case "b" and their "V" looks like a upper case "B". And don't even get me started with their ZH. I just...

My experience with P416b's has been quite good. Gains in the 70's to 80's, low leakage. Can't complain.

Also with 1T308Vs: those tend in the 40-60 range, but have extremely low leakage.

GT402b or E work quite well for a leakier, gainier transistor.

GT309b's are very high gain and very low leakage.

Lots of others out there. Not all usable. Many are just...garbage. For our purposes.

Theres something about the hunt for germs. Know what to look for, and it's not too terribly difficult. Sometimes you take a chance and get burned. Sometimes you take a chance and hit gold.
 
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