Fuzz Face Hum

[Chris S]

Hello,

I recently built a Fuzz Face and it sounds great only probelm is when I daisy chain it up with all my other pedals it has a horrid hum and clipping on the distortion. It works fine when I've got a wah pedal going as well and also works fine when it has it's own 9v power source. But I'd like to have only one power pack (all the other effects run off the one power pack)


My rig is

Brian may treble booster

Effects loop on / off box

Tubescreamer a 10 converted to and 808,

Crybaby (true by pass),

Hendrix Wah (true by pass),

Fuzz pedal (Tychobrahe +ve ground or Fuzz Face),

Danelectro mini delay,

Tuner.

Any help greatly appreciated  

Chris

[RDV]

Is the FF NPN or PNP?

Regards

RDV

[petemoore59]

I read this somewhere and it is true...the same is true of many whas'.
 I just run my FF's and wahs off of batteries, but there are power supply schems at GEO and other sources that your FF probably wouldn't be able to tell froma battery? Obviously I've never tried...hope this helps!!

[petemoore59]

Trying to share power withan npn device Will cause a direct short.

[gez]

What power pack are you using and what current can it spit out?  Just a guess here, but it maybe that it's wheezing under the strain of all those pedals and your fuzz face isn't getting it's requisite supply (perhaps the cause of the 'horrid clipping'?)   The hum could be a grounding issue.  I've got a vague feeling there's something over at GEO about this sort of thing...then again everything's vague in my world...

As an afterthought (isn't the edit facility a nice little tool), where in the chain is your fuzz face?  If you're feeding it from a low impedance source then that might be the cause of the naff sounding distortion.

[gez]

If you do a search for 'ground loop' at GEOFEX you'll find a nice little article on humming (it should be top of the list).  I'd link you to it but there doesn't seem to be a separate URL displayed.

[Chris S]

Wow! Thanks for all your replies!

In response to the questions...

The Fuzz face is PNP, the power source is a Boss regulated adaptor (9v 200ma), I'm in Australia so I'm starting with 240volts and I don't have the skills to convert a US power clean power schematic to Australian voltage (I don't care how many times I electricute myself with 9v I don't want to risk 240  :roll: ). I thought I might be running too many effects off the one source but got confused when the fuzz face worked fine with the crybaby on. As previosuly described fuzz face is right after a wah and just before a delay.

I'd really like to not resort to batteries if possible.

Thanks again

[Paul Marossy]

"The Fuzz face is PNP"

Is that positive ground, or negative ground? May be a factor...

[Chris S]

It's negative ground. the tychobrahe in the same box (that doesn't hum) is positive ground I get two power sources by using the The max1044 chip

Chris

[Paul Marossy]

Negative ground, huh? I just built a '69 not long ago and I don't have any hum. Weird...
It sounds like a ground loop problem. You could try using shielded wire on the input and/or output. That might make it go away.

[Chris S]

Finally I have isolated my problem but I am not sure what this means. My problem is having my TS10 (moded to an 808) before the fuzz face. Put it after and it's fine. But before and it casue the fuzz face to sound like it's not getting enough power or something. I am guessing it is something in the by-pass curcitry for the TS10 (Grrr) any suggestions really appreciated

[RDV]

Your fuzzface does not like the buffered output of the TS-10/808. You'll almost have to put the FF first in the chain, or at least put only true-bypass effects in front of it. I've given up on the standard FF, and I've got a really good one(aNaLogMan Sunface). I prefer the sound and consistency of my good old Rocket.

Regards

RDV

[Chris S]

Another revision update...

I have 4 non true by pass pedals... The tube screamer in front makes the fuzz face (and tychobrahe - to a lesser extent) sound bad (like it's not getting enough power so it has a horrible clipping sound) but put them in any order and it seems to have the same effect only to a lesser degree.

So I'm thinking I need to do something with the fuzz face and Tychobrahe, a bufferiung curcuitry perhaps?

Thanks for your help again

[RDV]

The Rocket is basically a buffered FF....with a twist
When you add a buffer to those 2 effects, their character will change, maybe not for the better, remember, it's a buffer and a low impediance source that's loading them down in the first place. R.G. should kick in here someplace :roll:
I'd just put em' first in the chain if I liked their sound as they are.
Just my personal take on it.

Regardo

RDV

[Chris S]

Unfortunately I've really got my heart set on tubescreamer then wah then Fuzz face.  

I tried playing my guitar with volume on one and the FF (in the chain) sounds fine.  I thought of this when I noticed that the start of the signal from the FF had a horrible clipping sound but the trail didn't.

Since the only other time the FF sounds okay (apart from out of the chain of the other effects) is when the wah is on I am wondering if their is part of the wah (crybaby) curcuitry I could permanently put infront of the fuzz face.  :roll:

thanks

Chris

[Chris S]

Okay this will sound embaressingly simple I think.

I had a look at the schematic to most of my other guitar pedals and they start with a 0.1 uF Capacitor. The Fuzz face starts with a 0.22uF Cap. So I put a 0.1 Cap infront of it and all the problems have gone.

Anyone who could tell me why this works I'd be greatly appreciative.
:?

[gez]

The fuzz face has low input impedance and loads a guitar pickup quite significantly.  The design of the circuit compensates for this.  Any deviation from the norm, i.e. feed the circuit from a low impedance source such as the output of a tube screamer, and you're driving the circuit too hard - this is why turning your guitar volume down restores the true FF sound.

It seems to me that what you want is the reverse of a buffer- something with high output impedance which can in turn be loaded by the FF.  What you could do is set up a simple Common Emitter circuit with unity gain and use a large collector resistor - it's value equivalent to the internal resistance of your guitar pickup?  This 'might' work.

[gez]

Bugger!  Didn't see this second page! (I've just woken up).  

Reducing the cap value cuts some of the lows, which were probably driving the circuit too hard (see above drivel)

[Chris S]

Gez thanks for your "above drivel" is there anywhere where I can see a schematic for "a simple Common Emitter circuit with unity gain and use a large collector resistor - it's value equivalent to the internal resistance of your guitar pickup"

I am a novice

:oops:

[gez]

I really must stop making 'early morning' posts!  A bit of my reply was 'arse about face'; I said that the design of the circuit compensates for the loading effect of the low input impedance, but it's more likely things were the other way round - the input impedance was lowered to make the circuit sound decent at high gain.

Anyway, as far as the 'buffer' goes you're probably best off with a MOSFET rather than a BJT.  If you were to use a common emitter circuit with a high collector resistance you'd need to set the quiescent collector current quite low and this might be a problem with some BJTs (then again I'm not averse to talking complete bollocks).

You 'could' use a n-channel MOSFET with a 10k drain resistor (for starters) and a 10k source resistor.  Connect the gate to the wiper of a 100k trimpot via a IM resistor and connect the outer lugs of the pot across the rails.  Move the wiper up from earth till you read 2.5V at the source.  The input cap attaches directly to the gate, the output cap comes off the drain.  

The above circuit has an output resistance of 10k.  This would be loaded by the low input impedance of the fuzzface and 'might' work at sorting out your problem.  If loading is too severe, you can start increasing the value of the drain and source resistors - keep them equal value and adjust the trim pot accordingly (this is why I recommended a MOSFET - the drain current may get quite low).

If all this is Chinese get back to me and I'll do a schematic for you.