MK3 transistor recommendations?

[carboncomp]

Could I get some guidance on what transistors I should look at for an MK3, preferably affordable and easy to find?

Assume I want lower hFE for the Q1 & Q2 being a Darlington pair, and then something a little higher for Q3?

[bmsiddall]

Greetings from Australia.

Just built a couple of buzzarounds- 1 npn and the other pnp with a charge pump. Have pretty much followed the recipe of low leakage (<50uA) and hfe around 50 for q1 & 2. Transistor types don't seem to matter, so i generally default to cheap, low leakage russian transistors for these. Previous experience with buzzarounds and mk3s suggest you'll still get great results with substituting low hfe silicon xsistors here if you have them.

Q3 will fire up with a range of hfe (have tried these from 40-130 or so), but a little more leakage is required.  For my npn buzzaround i tried a wide range of leakages (up to 500uA) and transistor types- the winner was a dirt cheap MP38A at 93 hfe and 150uA leakage. Sounds incredible!

Have also had good results with silicon in q3, but you'll need to simulate leakage. Think General Guitar Gadgets has a schematic for this.  Easy to make Si and Ge switchable for q3 if you're so inclined too.

[andy-h-h]

Just to bump up the Australian factor yet again...   

A MKIII is a very forgiving circuit when it comes to transistors.  Definitely low gain for the darlington, or you will end up with a fuzz control that does almost nothing as the signal will be coming into Q3 really hot.  I like a couple of OC45s here (but practically anything low-gain will work).

Q3 does need a bit more gain to get some life out of the pedal - a standard AC125, AC128 type transistor will do just fine.  I've used some cheap SFT transistors from Eastern Europe that were great, there's a lot of Japanese transistors out there for bargain basement prices too.   Do not waste money on fancy transistors for a MKIII - I've tried a few and they sound almost identical to their much cheaper cousins. 

If you end up using soviet-era transistors, apart from pin-out differences, sometimes the base is connected to the body of the transistor - so don't let them touch each other.

[carboncomp]

I've used some cheap SFT transistors from Eastern Europe that were great, there's a lot of Japanese transistors out there for bargain basement prices too.

Interesting, never used Japanese Ge transistors before. Is there a resource anywhere online that shows equivalent to say the OC range? 

[FSFX]

Interesting, never used Japanese Ge transistors before. Is there a resource anywhere online that shows equivalent to say the OC range?

Maybe something like this?

https://ia802206.us.archive.org/2/items/jap-tr-sub-guide-1975-a/TR_substitution_1975.pdf

Or this -

https://nvhrbiblio.nl/biblio/boek/14-2nd-Transistor-Equivalent.pdf

[duck_arse]

struth cobbers, I'm in. I thought the general concensus for mkIII Q3 was more leaky, because it biases via leakage. I'm messing w/ the buzzaround-kinda at the moment, and it strikes me from discussion "about that diode" in another thread that the buzzaround circuit would not need a leaky Q3, because it has bias via the sustain pot.

I've settled on a [pos ground] Sziklai pair as a bazz fuss Q1/2 section in mine and 2N404 at Q3. but this is probably not the thread for the buzzaroundalike bias question/discussion, so I'll stay schtumm.

[andy-h-h]

I've used some cheap SFT transistors from Eastern Europe that were great, there's a lot of Japanese transistors out there for bargain basement prices too.

Interesting, never used Japanese Ge transistors before. Is there a resource anywhere online that shows equivalent to say the OC range?

If you google transistor equivalents book, you'll find a few pdfs online.  Japanese transistors are a little different to OC transistors, but keep in mind that everyone was making radios and small amplifiers back in the day using the same basic circuits, needing similar parts to function.

example: 2SB89 = AC128  2SB45 or 2SB101 = OC45