MP15A and GT308G germanium transistors any good?

[snow123]

GT308A

35/0
37/0
37/10
27/0
24/0

Here is something else. MP15A
Transition Frequency (ft): 2 MHz
Collector Capacitance (Cc): 50 pF

GT308A
Transition Frequency (ft): 90 MHz
Collector Capacitance (Cc): 8 pF

GT308G
Transition Frequency (ft): 120 MHz
Collector Capacitance (Cc): 8 pF

You can see the GT are more of a RF transistor. higher freq and a lot lower capacitance. You may have to put a 47pf cap across C-B when used in a fuzz. Making good RF transistors with higher gain/less leakage was always a problem back then.

the karma suture already has that 47pf cap across the C-B, and im assuming i would remove said capacitor when using the MP15A, correct?

[andy-h-h]

Hello - given the low price, just buy some and give it a try on a breadboard.  You might be overthinking this.   

[antonis]

Snow with germanium — what could go wrong? 

I suppose we should be getting worried by now..

[DrAlx]

Not come across the GT308G before. 
I did try some 1T308B (the military spec version of the GT308B) in a fuzz before.
Capital B is "V" in Russian, so really should have called this "1T308V".

Note datasheet (link below) has info for "a","b","v" versions of the 308, with "v" (i.e. capital "B") version being the highest gain.
Leakage was very low, but hFE was not as high as I expected.
When I got hold of the datasheet I saw why.

Graph shows hFE close to 200 but that is for 60mA of collector current.
At the much lower currents of a typical fuzz design, hFE is way lower.

https://alltransistors.com/adv/pdfview.php?doc=gt308a-b-v_1t308a-b-v.pdf&dire=_russia

There were also lots of short bursts of "fizz" noise that would randomly flare up out of nowhere and then die away.
I never got to the bottom of that.  I ended up using AC128s.

[snow123]

Also, how do GT313V transistors actually measure? Asking 'cause the GT313 series as a whole has a super wide hFE range, and I'm wondering where within that range, they actually measure.

[antonis]

@snow123: Jeanne d'Arc is considered the 1^st person burned at the stake due to repeatedly quoting herself..

[Finom1]

Hello,

I found someone on eBay selling the + 50pcs 1T308V ~ 2N2048 (Russian1Т308B) - Germanium vintage transistor USSR - https://www.ebay.com/itm/174668870744

I contacted him, and he said he has one lot left that is not listed at this time. Just email him and he will provide information.

Dmytro, is great to talk to and has a lot to offer on his ebay store. The price is right!!!

[brett]

I've made a few pedals with GT308s.
The last one had two with hFE of around 60.

I say "around" because collector current, temperature, DC vs audio signal and more affect hFE, and people fail to compare on an equal basis.  Mine were measured at Ic = 1 mA DC and at 18C.  Around hFE = 70 at 28C?
In any case, they don't leak (significantly) and are very quiet.
In my opinion, better than NKTs, OCs, ACs and the like, that although they reportedly have voodoo magic, that presumably refers to just the good ones.  Whether "good ones" are three in ten or two in fifty, I leave to others. But in this context, I'd say 8 out of 10 GT308s are good.