Are PNP germaniums with hFE of 50 suitable for fuzz circuits?

[luap77]

Hi,

I have a bunch of 2SB75 germanium PNP transistors, all with real gains in the 40-55 range (after subtracting leakage). Is this too low for use in fuzz circuits? If not, what's the trick to getting them to sound OK, given that they are lower then the recommended gain of 70-150 for a good sounding fuzz? Is it as simple as putting in a higher gain transistor (e.g. 200) for Q2 in a fuzz face etc?

I'd really like some opinions from people please. Thank you.

Paul E

[MetalGod]

they just wont FUZZ as much in the FF circuit - try it, you may like it.

[tester]

I agree, lower gain hFE in a Fuzz Face can work very well. For some people, the higher hFE is too much.

[luap77]

Can a fuzz face be made to fuzz as much as a regular one if I use Q1 = 50 hFE, and simply make Q2 a higher gain than the recommendation? Or, is there a trick to biasing the low hFE transistor differently or running it at a higher voltage etc?

[Sir H C]

Yes.  For instance in the FF circuit, if you reduce the collector resistor on the first stage transistor, you can drive it with a lower impedance making up for some of the Hfe/beta loss.  So you can use these for the second stage in a fuzz face, they are not really suitable for the first stage as the input impedance will be quite low.

[luap77]

So, is this trick verified in practice? Anybody tried using lower gain germaniums in fuzz faces with success? Can you please provide me with more details?

Thanks

[hairyandy]

Those would make a pretty good Rangemaster or full-range germanium boost as well.  Check out Dragonfly's layout gallery for a bunch of different pedals that would work.

Andy

[petemoore]

  Check out the Rangepig.
  You can 'Darlingtonize' and control gain of the 'two transistors becoming one...however you may get more noise...if the multiplied leakage 'adds up to do so'...big increases in transistor gain...I would socket to 'interview candidates' for best performance.
  So yes...'but'...not as a pop in...as a 'build around and work with it' type affair...I got excellent results with the Rangepig, higher gain sound and really no noisier than a Rangemaster...
  The Colorsound Overdriver {IIRC} uses a couple transistors darlington configured...I'm not sure what the gain/leakage recommendations would be..
  I would suggest getting the gain up/noise down with a Darlington stage of transitora, then stick that in a Fuzz or as pre-Fuzz or...
 

[Dragonfly]

  Check out the Rangepig.
  You can 'Darlingtonize' and control gain of the 'two transistors becoming one...however you may get more noise...if the multiplied leakage 'adds up to do so'...big increases in transistor gain...I would socket to 'interview candidates' for best performance.
  So yes...'but'...not as a pop in...as a 'build around and work with it' type affair...I got excellent results with the Rangepig, higher gain sound and really no noisier than a Rangemaster...
  The Colorsound Overdriver {IIRC} uses a couple transistors darlington configured...I'm not sure what the gain/leakage recommendations would be..
  I would suggest getting the gain up/noise down with a Darlington stage of transitora, then stick that in a Fuzz or as pre-Fuzz or...
 

which brings up a good point...combining lower hfe germs and silicons to get usable ranges for FF's and other circuits.  A dual "darlington"  configured FF would be quite possible, and with proper tranny choice, could sound quite good.

[mac]

I breadboarded a FF and a TB mkII and 3-knob with out-of-spec 2N388 texas inst.
In the case of the FF I used a hfe: 50 & 60 pair. In the TBs a hfe: 40, 50 & 60 set.
I did really like both very much. In the case of the FF maybe a little loss of final gain but nothing to worry about. The TBs have lots of gain even with low gain Ge.

My advise is, try them and compare with a higher gain pair. If you like it build it.

About using low gain ge in darlington pairs, I did that with the rocket (sshhhh do not tell aron )
There is a post somewhere in fuzzcentral.tripod.com forum.
I guess the trick is to get some very low gain hfe?30 & very low leakage ge. Good candidates are AF106, 2SA53 & 2SA101/2 (AA).

mac

[luap77]

Thanks for the suggestions!

I've got a fair few of these, so I didn't want them to go to waste. My next step is to read up on Darlington transistors.

Cheers,

Paul E

[petemoore]

 A 3 transistor Fuzz, tuned for 3 'LG' Ge's..
 

[mac]

I've got a fair few of these, so I didn't want them to go to waste. My next step is to read up on Darlington transistors.

If you take a look at the TB 3-knob the first stage is a darlington pair with a 10k from q1 emitter to gnd.
Recall that q1 leakage will be "amplified" by q2 so use low low leakage ge. Not a big problem if the transistors are not hissy. Search for the sound of leakage by RG in the forum.

mac