strange fix for a tonebender mk11 pnp pos grnd!!

[bobster]

hi,
i recently made my 2nd pedal , a tonebender from this layout in the gallery -  http://aronnelson.com/gallery/Richard-Boop-RLBJR65/MarshallSupaFuzz [ i did the solasound version ]

i used 3 Mullard OC81s salvaged from an old radio and when i got it going , it boosted hugely and sounded pretty good and nasty but didn't clean up too well  so i did some measurements-
Q3 collector voltage was 9.7v .   i had to put a 68k resistor in place of the 8k2 to get voltage to 4.5v!   this totally killed the volume and the pedal was super quiet compared to bypassed signal........
so here's the rub........
i still had a mullard OC45 layin around from the radio [ well known to be low low gain and not very useful for fuzz face etc etc ] so i popped it in to Q2 position just for laffs to see what happened...................
interestingly , i now get about 4.7v on collector Q3 and still get a good boost when pedal activated - also , it cleans up a bit better. sustain is just a little less than before but this is through a low volume practice amp so it might balance out good when hooked up to the gig rig [ marshall 50 watt '69 ]   
quite pleased with this but i suspect now that i may basically have the rough equivalent of a germanium  fuzz face in my hands!

a weird fix and probably not grounded [ no pun intended ] in science but hey , it will do for me!
cheers - rob

[wademalorgan]

I had the same thing happen to me.  I ordered my transistors from smallbear and used the correct resistor values given (except for the trimpot on the collector of Q3).   When i adjusted the trimpot to get to -4.5v I lost all volume.  The circuit sounded way better but the output was far to low.  I soon got fed up and stopped working on the circuit.  Maybe if I keep trying different transistors for Q2 like you did, I'll get better results.  I just figured the three matched transistors from small bear would work together.

wademalorgan

[bobster]

yeah , let us know how you get on...

if it helps , the trannies i used were old style mullards and Q1 [ OC81 ] was about 65 hfe , Q2 [ the oc45 ] was 34 hfe and Q3 is an oc78 at 96 hfe.

although not recommended by the circuit designers , i find this a good mix and it gives me 4.7 volts on Q3 collector with resistor of 8k2...............

sounds much more musical now and cleans up well sweeter than before -
good luck
bob