PNP "Negative Ground" FuzzFace weird noises SOLVED

[Kleber AG]

Is there an explanation for the difference betwen "PNP" positive X negative ground?

Just ocurred to me that the fuzzes circuits usually don't have a power filter cap from V+ to ground...
so, at a negative ground the circuit will have roughly the "collectors" at the box chassis (what is suposed to be a shield protection)...
but, the point at the circuit that actualy should receive what you would want to have filtered is the point where the emissors connect...

Ahhhggg (I'm bad on english and horible on electronics, but this is what have come to my mind)
Am I totally lost on it?
If not, does a filter cap from V+ to GND just solve this situation I've described or not?

At least for me it worked like a charm, now it's very well biased, no oscilations (even with higher gain on Q2).
First I've tried a 22uF filter cap from V+ to GND, but it just doesn't worked, then I raised the cap to 220uF and BINGO all noises went away.

That kind of noises seems to be present just when you lower your guitar volume knob too much for a really "CLEAN" tone from a dimmed fuzz face.

I'm very happy with it now and the best of all: It's an easy face PNP but with "Negative Ground" so it's compatible with any of my pedals.  

I encourage you to try that on your FuzzFace, JUST watch out the cap polarity make sure it's well oriented.

Regards
Kleber AG
PS: Thanks a lot to Jason G. and Arn C. you guys help'd me so much!  

[rx5]

Hello Klebeg,

Just wondering if it would also work with a PNP postive ground Tone Bender ??

[Kleber AG]

I have not build any fuzz based pedal that is PNP positive gnd, in fact this is my first fuzz (I loved).

I was having weird noises, misbiasing, mainly when turning the guitar volume control down to achieve a "clean" tone from the fuzz.
And some people that tried the PNP negative gnd reported having this problem too, then they just converted their circuits to PNP positive gnd and all the noises went away.

I really do not wanted to make my easy face (thanks to Joe G) a positive gnd then I have thought about that, it worked perfectly for me, you may have to raise the filter cap capacitance until the problems stops.
If you are having the same problems even with a positive gnd, it may help, not sure.

BTW: I would like to thank Jack Orman for his great article on PNP positive GND at the AMZ site.

Could someone take a look at what I wrote on the first post, and check if this makes sense at all? Please.

Best wishes
Kleber AG

[Kleber AG]

eerrr... sorry
I just re-read the great article "Positive Power for the PNP Fuzzface" at http://www.muzique.com/lab/fuzzface.htm and it's right there...

From Jack Orman:

If for some reason oscillation does occur, a quality low esr capacitor from the positive supply to ground will solve the problem everytime since it effectively places the power rails at the same ac potential. Put the capacitor on the pc board if possible. Also keep the positive and negative power wires as short as practical. I've used this method with two different fuzzface derivatives for years with no problems and one of them has a quite long positive power supply wire.

Sorry for the confusion, at least it confirmed what I was wondering, filtering is the right solution for the PNP negative gnd.  

Thanks Jack for always been there... heheheheee :lol:  when we got in trouble we just need to check our amazing resources!

Good New Year everyone!
Kleber AG

[rx5]

my first try with converting my PNP ge FF was a complete failure... It oscillated when Fuzz was set to full.... hadnt had the thought of putting a Filter cap (>220uF) at the supply lines...

and Iv dissasembled my FF in favor of a Ge PNP TB...


-RAlph