Revisting my Ross comp -> unwanted dirt

[Seljer]

I made this one a while ago but I didn't get to play it very much (those pesky expensive 9v batteries), messing around with it today I've found that it adds a rather noticeable amount of dirt.

comparing to the fuzz central voltages: http://fuzzcentral.ssguitar.com/ross.php


supply is 9V
Vb is about 2.7V

and I think the main problem is Q1
E 7.6V
B 1.25V
C 1.34V
I used 2n3904s all over the board.  Otherwise the thing works fine, except for an that slight distortion. Where should I be looking?

[MartyMart]

1 - the trim pot, set it so the chord decay is clean or just used 2 x 1k's as suggested here.
2 -  check your caps, I had a 1uf reversed and it caused lots of hiss and
background dirt .. til i spotted it !

MM

[Seljer]

I replaced Q1 with a 2n5089 and theres barely any difference, voltages are roughly the same too. I probably should get an audio probe thing together to check what its like after that transistor if it is the culprit.
The distortion only happens when I hit the thing hard, its not there with softer picking. But I can't really tell if it gets worse with the sustain control up higher.
I don't think its in the actual decay section, the decay sounds fine.

[Papa_lazerous]

Could be wrong but maybe your bias is a little off and causing some clipping on notes when you really hit the strings.  I built one the other week and changed the value of the 27K resistor on the tonepad layout up at the top left corner where Vbias is set.  Cant think what I changed it to now to get it right as I'm at work and circuit is at home.  Try lowering the value to say 22k as see what you get.  Let me know if it works for you