Thundertomate Cow :)

[Bernardduur]

I was on the search for some new fuzz; a fuzz that is not as harsh and thin sounding but sounds big and round without getting to use germanium transistors.

So I downloaded Thundertomate's schematic such a while ago and was intrigued with it('s name)..... it is basically a Silicon Tonebender with some additional mods but does not sound ANYTHING like the Tonebenders I build (or the former tonebenders just sucked); it is open, big and full sounding without getting too muddy..... The additional switch switches in more or less gain and making it a great OD / fuzz unit. Maybe a momentary switch will do great here.

I used, as suggested, BC109B's and Q3 biased at 3-3,5V with the 5.7k resistor at Q2's collector.

This is a keeper; I know for sure!
Thundertomate, thanks for the great idea!

Small issue:
I can't really bias the device propery as the collector voltage of Q3 jumps up and down when I play. If I stop suddenly the bias gets lower then 1.6V and the volume is cut and comes back up slowly

[Bernardduur]

Someone? Is this normal??

[stm]

Could you point to the schem?

[Bernardduur]

The scheme was taken down as the site went down...........

And it is not up again

I will post it here as it was posted originally by the owner, who is also a member on the board. If anyone has any objection please mention it and I will remove it again!

Schematic

[Bernardduur]

Main weirdness: bias of Q3 moves when playing from 3.5V to 0.8V

On this board it was suggested to bias Q3 with the 57k resistor on the collector of Q2 (to around 3 - 3,5V on Q3)

[stm]

I'd suspect about two electrolytic capacitors: C4 and C10.   Check polarity, as reversed polarization on an electro may cause leakage.  Also, C10 (22u) seems too small to provide proper filtering at the R8, R10 and R16 node.  Check polarity, if the value is right (and not 2.2u by mistake, for instance).  Also, I'd suggest increasing it to at least 100u to see if it helps stabilize biasing.

[Bernardduur]

Both caps are orientated right. I tried enlarging C10 or removing it but still the problem stays

[stm]

Both caps are orientated right. I tried enlarging C4 or removing it but still the problem stays

C10 is the cap to enlarge: 22uF -> 100 or 220 uF

[Bernardduur]

Woops

I meant C10

[Roberto]

If anyone has any objection please mention it and I will remove it again!
Schematic

No problem at all, that's ok.

Biasing must be done with input grounded. Anyway, I don't remember to have that problem with Vc(Q3) voltage. 22uF is ok for C10 if R16 = 220 ohms if I remenber right (check R16 value too!). Good luck  

[Bernardduur]

Thanks man!

I'll try!

[Bernardduur]

Hmmm

can't keep Q3's voltage constant; it keeps dropping to around 2.8V in rest (input grounded)

it is quite annoying as I can't keep it steady the unit will gate when I play

[Steben]

This cow should sound somewhat treblier (especially clean up) than let's say a TB MkII, right, since it has about ten times the input impedance? That would explain the "open sound".