Fuzz Face Noise

[quad]

Hello,

I've recently build a Fuzz Face pedal using this schematic:



The AC128 transistors were used. I did a true bypass including an LED.

The fuzz effect itself seems to work, but there's some kind of weird "buzz" noise. This "buzz" is most evident when the guitar volume pot is turned all the way down. It tends to clean up somewhere in the middle, but the sound is lost too. It gets noisy again at higher volumes.

Here's a sample:

Buzz

00:00 - 00:09 (Clean sound)
00:09 (Fuzz effect on)
00:17 (Guitar volume knob turned down to somewhere in the middle)
00:25 (Guitar volume knob going down)
00:32 (Guitar volume knob all the way down)
00:38 (Guitar volume knob all the way up)

Can't figure out what the problem is 

[Tony Forestiere]

It sounds like 60 cycle hum to me.
Is the circuit on the breadboard/open PCB, or boxed up?
All grounds properly star-grounded?
Wall wart or battery power?
Any fluorescent lights/ballasts nearby?
Just some silly thoughts from a silly guy. 

[quad]

It sounds like 60 cycle hum to me.
Is the circuit on the breadboard/open PCB, or boxed up?
All grounds properly star-grounded?
Wall wart or battery power?
Any fluorescent lights/ballasts nearby?
Just some silly thoughts from a silly guy. 

The circuit is in a box. Grounds are not connected to the chassis, if that's what you mean.  Powered by a wall wart (tried both - same result). No lights nearby. 

[CynicalMan]

The grounds should be connected to the chassis. I wouldn't worry about star grounding for a pedal, though. If the wall wart is unregulated then it will cause 60Hz hum, but a battery won't add any.

[petemoore]

  Try it with another guitar, to eliminate suspect guitar wire or pot.
    A different short cable.
   All grounds common?
    Except that the FF input can be sensative to just about any slight disturbance, almost like theres a resonant frequency in it and any little thing sets it off..
  Another try is the small-teeny Q2C/B cap to rolloff a touch of treble gain, could be placed at base/gnd., a pre-try might be roll the gain knob back a touch.

[pinkjimiphoton]

not to sound retarded, but are ya using single coils?

it sounds to me like a low frequency oscillation...connect try connecting the circuit ground to earth on one jack, also double check your soldering. if that doesn't do it, try making sure you don't have a cap reversed. could be a ground loop, too...i'm not used to positive ground circuits, so not much help here. it sounds like something is triggering some kind of sympathetic oscillation, i've had that happen a few times, and fresh solder and a hot iron seemed to clear it up. be especially careful of lead length with caps, long leads can lead to all kinds of weird stuff. good luck man!!!


also, if you used sockets for your transistors, make sure the trannys are seated properly in them. i have found that sometimes that can make weird oscillations, too.
the pedal sounds good tho!! so it's probably something stupid..make sure all flying leads are as close to the metal box as possible, you may wanna see if you can get it to do it with the box open, if it does, try moving the leads around just a little bit and see if it goes away. high gain stuff can be kinda funky about lead dress sometimes in unpredictable ways!!

[quad]

Thanks for all the input I'm positive I'll fix the noise.

[eeijcon]

Hey Quad,

Did you ever fix this problem - I have the same thing now with a negative ground PNP fuzz face layout.  I works great when guitar volume is up but when I turn the guitar volume knob right down I get a loud hum.  The hum changes frequency when I turn the fuzz pot on the circuit.  I did an audio probe and found that after Q1 the hum is introduced and goes on to be amplified by Q2 and there after is tamed by resistors or pots on it's way out.  I would have suspected a bad solder at the transistor but the thing that confuses me is why is it fine when I turn the guitar volume back up (disappears when the guitar knob is on about 3). I resoldered the transistor holder anyway but no difference.  I've tried the usual changing the trannys, checking all grounds, cleaning the PCB etc to no avail.

Did you ever solve the problem?

Cheers,
John.

[lars-musik]

I'd like to re-animate this old topic.
I built a negative ground NPN (2N396A and BC108A) Fuzz Face. Now the guy I gave it to experiences a loud hum when his guitar volume is turned down. He tried with singlecoils and active humbuckers and he uses a decent power supply. I thought that during shipping some ground connection might have come loose, so he sent it back to me for checking. (Un)fortunately the pedal works just fine with my setup. No hum (humbuckers and rickenbacker Style singlecoils). I checked all ground connections and everything is where it should be.

Still, I would like to help out. Do you have any idea where else to look?

Thanks!

[antonis]

Oversizing 100μF to 470μF and placing a 10-47R resistor right after Schottky may solve the problem..
(if it's PS originated..)

[lars-musik]

Oversizing 100μF to 470μF and placing a 10-47R resistor right after Schottky may solve the problem..

Thanks. I will do that.

(if it's PS originated..)

He uses a cioks dc 10 that should be fine. But of course, maybe it isn't.

What else besides the PS could it be?

[pinkjimiphoton]

hey bro
sounds to me like either shitty grounding in the guitar itself ( very vERy common)
or check the biasing on the q's. certain ranges of bias will make the q's much noisier than others.
i'm battling this issue with the latest gizmo on my breadboard. sounds KILLER on some settings, but on others... hum city

[italianguy63]

hey bro
sounds to me like either shitty grounding in the guitar itself ( very vERy common)
or check the biasing on the q's. certain ranges of bias will make the q's much noisier than others.
i'm battling this issue with the latest gizmo on my breadboard. sounds KILLER on some settings, but on others... hum city

I'm with Jimi-- maybe bad guitar ground or shielding?

Try hooking a test lead to the guitar bridge, and ground jack side.. see if it goes away.

MC

[italianguy63]

BTW schematic looks absolutely good.

MC

[lars-musik]

Thanks for your input, friends. As I cannot get this thing to hum or buzz in my setup I tried to implement your ideas in blind flight. I added a 220µF to the PSU section as well as an 100R serial resistor. Contra radio interference I put ferrite beads on the input wires prophylactily. Lastly I added a trimpot of 10K to the input. Maybe my client can dial in something against the noise without disturbing the vibes (he really loves the sound of the pedal besides the hum when he turns down the volume).

If the Decimators weren't such a pain in the neck to build, I'd simply offer him one of those.

[antonis]

prophylactily.

<spam on>



(Sorry Lars, but in Greek that's the adverb for a condom..)

<spam off>

[lars-musik]

Thanks Antonis,

you are a constant source of wisdom in this forum!   

I really didn't know that. To my knowledge, we don't even have an adverb relating to condoms in Germany. But then again - I still haven't fully grasped impedance so I will not start to wrap my head around te grammar of contraception!