Rocket Fuzz Question

[Shimmer]

For my second ever pedal build I am trying the Rocket Fuzz.
http://www.generalguitargadgets.com/effects-projects/fuzz-tones/rocket/
I have it breadboarded but with BC550 transistors as I cant yet find the 2N5088. The "Drive" control however seems to work more like a volume pedal - when it is to the left it cuts all the sound. Is that normal?

I was thinking I might instead try and use it as a control to add in a larger capacitor in parallel to C2 (a 683 sounds nice and fat to my ears).

Cheers

[BetterOffShred]

Many circuits have a control other than volume that will entirely kill the output of the device.   I don't like controls that can kill volume other than the actual volume pot myself, putting a 2k or so in series with some of them will prevent this, but that's dependent on circuit design.   

550's come in a few gain ranges, if you look at the datasheet they have A, B and C designation, the C's being the highest gain if memory serves.  As long as your gain range is ballpark, I doubt you will gain (pun intended) or notice much difference..   but I could be wrong.   

[Shimmer]

Thanks for that. I measured the Hfe of them and they are lower than the 450 specified on the circuit diagram. But they still sound pretty great with a larger cap at C2 (I also increased C1).
But I think I will ditch the Drive for my build and include the control for including a small and large capacitor in parallel at C2.

[Mark Hammer]

Betteroffshred's suggestion is entirely appropriate.  The value of the added resistor will depend on your taste, and how subtle or intense you like things.  A 1k resistor will still allow for some output at minimum Drive setting, but will provide less "push" than the suggested 2k.

Chances are pretty good that the Bias control will permit sufficient adjustment that the BC550s, whether A, B, C, or ZZ, will work just fine.

Two suggestions I can make once you get it working fine:
1) C2 sets the low end.    Use .0022uf instead, and a toggle to add the .01uf cap in parallel for a thin/thick adjustment.
2) The 47k resistor that provides feedback from Q3 to Q2 can be productively used to create "glitchy" effects.  Try adding 47k to 150k to it, and see if it yields something that appeals to.  You can even consider a 100k pot to get variable glitchiness.

[Shimmer]

Awesome - thanks for both of those suggestions.
I definitely love the sound of this thing - but am still enjoying the fine tuning of it. I'm very much a novice so still trying to figure out what the different components do and what effect changing them has.