silicon fuzzface close to Xcellent-advice welcomed to finish off

[bobster]

hi folks- [ i have searched much on the forum but have a couple quick questions..................]
ive just completed my 3rd build from this http://aronnelson.com/gallery/album17/SILICON_FF_VERO
layout and would like to get some advice on getting it close to perfection/sweet spot territory !!

at present it cleans up great with my old style strat /valve amp and sounds sweet everywhere on guitar volume pot except at about '9-10' where it becomes very muffled and nasty and seems to lose all treble.........
there is the usual slight oscillation towards and of fuzz pot travel so i just back off a bit there
i have two old BC108's in . Q1   hfe is 422 and Q2 is 507 . [input cap is 2.2uf and i have made output cap also 2.2uf . i have fuzz pot at 2k]
here are the voltages [ i used a 10k pot to help with bias on Q" ]

Q1,    C   1.16           Q2,     C   4.62
         B    0.58                     B   1.16
         E    0.00                     E   0.68

should i be thinking of lower gain transistors?   is there any other things i can do to help smooth her out a bit and get nearer a sweet spot?
pre gain pot maybe??    if so , how do i wire it in?

any advice most welcome as i think i'm gettin close to a real belter here !!
cheers - rob

[bobster]

bbbb bump

[mac]

I suggest you to use low gain silicons, Q1 (60-70) & Q2(70-100). Maybe a pair of BD139, MPSA42, 2N2219, etc.
To get rid of the highs you can put a 47-200pF cap from collector to base on both transistors, a 0.01-0.1uF in parallel with the 470R resistor, or a 470pF-0.001uF in parallel with the 100K feedback resistors.
The input pot is a nice idea. It may be helpulf when using a wah in front of the FF. 50 - 100K works fine.

Look for the Axis Face at
http://fuzzcentral.tripod.com
or dig in the forum.


mac

[petemoore]

  Something like ~.0027uf from Q1B to ground..another option to rolloff highs.
  I'd probably try only one at a time and however many / what values sound best to you.
  I like the cap on the top of the 1k on the
  http://fuzzcentral.tripod.com
  Axis Face