alternate gain values for q1-q3 in a tonebender Mk II

[mordechai]

On the DAM forum, David Main posted some pretty hot values for his old marshall Supa Fuzz (q1 around 160something, q2 a bit over 200 and q3 around 180something if I remember correctly).  I am sure with proper biasing these increased gain values can yield very tones characteristic of the ~70-70-100 Hfe values as per Fuzz Central.  But I am curious about the increased Q2-to-Q3 gain ratios.  On this board, a few of you have suggested that a Q2 with higher gain than Q3 is a good thing...I have tried it within reason (Q2=120, Q3=108) and the end result was typically tone-bender-y.  But what does having a higher Q2 value actually accomplish when the difference between Q2 and Q3 is more substantial, as per David's comments about his Supa Fuzz trannie values?

[LucifersTrip]

The Q2/Q3 gain difference in that Supa Fuzz was not substantial

http://dam.10.forumer.com/viewtopic.php?t=779&highlight=collector+voltage

Q1 - 174
Q2 - 208
Q3 - 194

I have build numerous MKII's and variants and so far, my favorite is easily that super high gain Supa Fuzz. It is a killer.

Remember, the leakages are nearly as important as the gains, so the fact that you have Q2 a certain amount higher than Q3 doesn't really mean much unless you know the leakages, also.

The Supa Fuzz I built had hfe 244, 193, 213 ...all leak under 150uF

Remember, the Fuzz Central Q3C voltage is off. It's not 4.5V, but usually ~ 6.5 - 8v

[mordechai]

What if I have a Silicon Q2 with zero leakage at about 100-120 Hfe, and Germanium Q3 of 100-130 with leakage at around 100-200uA?   Do you see any potential problems with interaction with that scenario?

[LucifersTrip]

In my experience, all the MKII's I've built needed some leakage in each position to sound best...but not too much.

I actually made notes on my last one: If I used a very low leak Q2, the tone was sharper with less fuzz. I didn't like it. If  Q2 leaks too much, it starts to gate.

[mordechai]

In my experience, all the MKII's I've built needed some leakage in each position to sound best...but not too much.

And yet, some MKII circuits using all silicons -- I'm thinking of something like the Basic Audio Scarab -- sound really excellent and pretty darned authentic.

I wonder if using a lower value for the collector resistor on an Si Q2 might help shape the signal to interact with Q3 in a way more akin to a low leakage Ge in the Q2 position...