Silicon version of a Tonebender MK 1 ?

[Sparky]

Anybody designed a silicon version of a Tonebender MK 1 ?   [The original 3 tranny circuit].
I always wondered if some low gain transistors could work in a circuit like that.  I know there are silicon Mk 2  circuits but it's not the same thing...... I would think a MK 1 would be trickier.

[antonis]

I would think a MK 1 would be trickier.

It's your inalienable democratic right..!!

P.S.
Welcome..

[bmsiddall]

I built one a few years on perfboard using the basic design by Mac:
https://www.diystompboxes.com/smfforum/index.php?topic=101610.0
I used low gain silicon <100 hfe for q1 and q2, maybe 100 for q3 from memory?  I found it was a little tame and overdrivey with these values until i removed the 4k7 interstage resistors. I also removed the b-c caps to give it authentic silicon mojo    This transformed it into a killer fuzz that stacks up really well when A-B'd against my germanium mk1.  Recognisably mk1, with less velcro on the pick attack and less crackly decay but more silicon cut and aggression. 

I'm thinking of building a tagboard version and trying 180k for the q2 base resistor to see how that affects the pick attack.

[Sparky]

Thanx!    I happened to be looking at a bag of those transistors today.

I can't find any 4K7 resistors.... must be blind!

[bmsiddall]

Mac redrew it on page 2 of the thread with 4k7s.  I think to limit the signal to each stage from hotter transistors.

[Rob Strand]

If you want something else to try there was this trick where you use two transistors to make a single lower gain transistor,

https://www.diystompboxes.com/smfforum/index.php?topic=59405.0



You connect the BE junction of a second transistor (Q2) across the BE junction of the main transistor (Q1).
Ideally Q1 and Q2 are from the same batch. The raw idea sets R1=0.   The non-zero R1 is less fussy about
matching of Q1 and Q2 but has less gain reduction, and can be tweaked.

I'm not saying it's good or bad only something to play with if you only have high gain transistors.

[cctsim]

I built one with 2N2369s with gains between 60 and 70. The only changes I introduced were related to biasing. and 1Meg resistor from Vcc to the base of Q1 and a 120k resistor from Vcc to the base of Q3. Transistor numbering from left to right.

I also used a 1k linear pot as starve control to reduce the Vcc. This acted as a gate control and controlled the amount of fuzz too.

Overall, it sounded very good.

[Knobby]

If you want something else to try there was this trick where you use two transistors to make a single lower gain transistor

I read up on the piggy-back trick sometime ago in relation to simulating germanium fuzz faces, but it all seemed to go by the way when people discovered low gain power transistors and the like. I thought that you might be able to use it to have variable gain transistors, for example, use modern high-gain silicon transistors to make an all in one fuzzface that covered everything from low gain germanium-like to full out hot silicon. Perhaps individual front panel HFE controls might be a bit over the top, but switchable options could be usable. Another of those ideas to try things that I might one day investigate...