Tonepad Fuzz Face....im going crazy

Music · April 13, 2007, 09:31:32 PM

Hi, ive built the Tonepad version of Fuzz Face with negative and positive ground.
With the negative ground ive motorboating with battery or power supply.
With positive ground ive no motorboating with battery and works fine but i cant make it works with my power supply. Im using a homemade power supply. I need help with the connections for positive ground, im a little confused about it.
Thanks.

brett · April 13, 2007, 10:18:57 PM

For neg ground PNP you need a big cap to provide an AC ground from the negative supply. Hook a 220 uF or more cap between the supply and ground. Reducing the ridiculously big 2.2uF input cap to 1uF or 0.47 uF also helps.

Music · April 16, 2007, 10:39:00 PM

Hi, i did the modifications that you said, and now im crazy completely, the motorboating stills here. Now ive to think in use the positive ground that make no noises with the battery, but with the power supply didnt works. Im using the offboard wiring layout 3 at tonepad site, ive got some questions:
1st - Ive to use a stereo dc jack or mono w/switch?, isolate?(my power supply its isolated from chassis).
2nd - looking at the offboard layout wiring 3 at tonepad, what changes ive to do in connections(jacks)?.
Thanks.

R.G. · April 17, 2007, 08:16:06 AM

This question comes up so often that it makes me crazy.

If you build a PNP-based effect similar to the Fuzz Face with negative ground instead of the positive ground it was designed for, is has a reasonable chance of oscillating and motorboating. Sometimes it works fine, but sometimes it oscillates. The simplest way to fix this is to convert it back to positive ground and live with the power supply issues. In years of trying I have not been able to find a definitive way to fix the oscillation and motorboating.

In other words: DON'T BUILD A PNP BASED EFFECT AS NEGATIVE GROUND IF YOU'RE NOT WILLING TO LIVE WITH THE CHANCE THAT IT WILL OSCILLATE AND BE UNUSABLE.

I really wish Tonepad and GGG would put this warning in those projects. It's not doing a beginner a service to imply to them that they can just build these things negative ground and have it always work. Beginners, not knowing any better, read that they can just build them with inverted grounds and do so. They wind up here asking for help.

I think you're the second or third one this week.

Morocotopo · April 17, 2007, 10:12:09 AM

R.G. and / or admins, this (your answer) should go in the wiki /FAQ, I think.
I´ll try to put it there, but I´m not too experienced with forum operations. I don´t even know if I can do it or it has to be an authorized person.

Morocotopo

Morocotopo · April 17, 2007, 10:15:18 AM

OK, I just looked into the FAQ thread and R.G. already added this.

morocotopo

MikeH · April 17, 2007, 02:33:34 PM

Quote from: brett on April 13, 2007, 10:18:57 PM
For neg ground PNP you need a big cap to provide an AC ground from the negative supply. Hook a 220 uF or more cap between the supply and ground. Reducing the ridiculously big 2.2uF input cap to 1uF or 0.47 uF also helps.

Mine "motorboated" and oscillated, but then I read on here about the BFC (Big F'n Capacitor) trick mentioned above. I had to use a 1000uf to keep it from oscilating.

mdh · April 17, 2007, 04:23:46 PM

It seems to me that the general answer to the power supply issues is for us to just get into the habit of building (and recommending that others build) bipolar power supplies for our pedal boards. R.G. describes it here: http://www.geofex.com/Article_Folders/Power-supplies/powersup.htm. This way you can have positive and negative supplies referenced to the same ground. Make or buy your power cables, go to town with two contrasting colors of plasti-dip for color-coding, and you're golden.

Fp-www.Tonepad.com · April 19, 2007, 09:46:27 PM

Quote from: R.G. on April 17, 2007, 08:16:06 AM
This question comes up so often that it makes me crazy.

If you build a PNP-based effect similar to the Fuzz Face with negative ground instead of the positive ground it was designed for, is has a reasonable chance of oscillating and motorboating. Sometimes it works fine, but sometimes it oscillates. The simplest way to fix this is to convert it back to positive ground and live with the power supply issues. In years of trying I have not been able to find a definitive way to fix the oscillation and motorboating.

In other words: DON'T BUILD A PNP BASED EFFECT AS NEGATIVE GROUND IF YOU'RE NOT WILLING TO LIVE WITH THE CHANCE THAT IT WILL OSCILLATE AND BE UNUSABLE.

I really wish Tonepad and GGG would put this warning in those projects. It's not doing a beginner a service to imply to them that they can just build these things negative ground and have it always work. Beginners, not knowing any better, read that they can just build them with inverted grounds and do so. They wind up here asking for help.

I think you're the second or third one this week.

Can I quote parts of the above as a warning?

EDIT: I did have some warning, but I've added some notes to the project page.

d95err · April 20, 2007, 11:03:21 AM

I must have been lucky! Some of my very first pedal builds were a Fuzz Face and a Rangemaster. Both using PNP and both converted to negative ground. None of them has had any serious oscillation or motorboating problems...

searoad · April 20, 2007, 02:44:38 PM

not sure if this had been discussed before.
could we take the idea from zvex ff to build a negative-gound fuzz face?
i dont know how it works exactly...but it should be worth trying.

if this is about copyright or something plz pm me i would delete this post.

jonathan perez · April 20, 2007, 02:49:12 PM

ZVEX didnt invent the negative ground fuzz face

searoad · April 20, 2007, 03:03:24 PM

Quote from: thebattleofmidway on April 20, 2007, 02:49:12 PM
ZVEX didnt invent the negative ground fuzz face

im not saying fuzz factory is a clone of fuzz face.
but i thought it is a pnp based circuit and has the negative ground?

Fp-www.Tonepad.com · April 20, 2007, 05:42:09 PM

I find that the noise generated changes depending on how you have the guitar volume set, try that.

Also worth mentioning is that if you feed it thru a buffer that doesn't happen.

petemoore · April 20, 2007, 07:53:38 PM

Yupp, as soon as I saw that as the top FF entry at GGG I knew it would get built right or wrong and have problems, hard to sort out problem FF when it's a first.
I think/thank someone here, someone must have steered me in the right direction and I forewent the Neg/PNP thing.
IIRC I started with the schematic, saw there was 'extra' stuff going on, asked and was told a couple tales of nasty noises, that was enough.
IIRC the BFC fix doesn't always work, but would be a great 'option' feature.

Barcode80 · May 24, 2007, 02:14:38 AM

i just built the tonepad neg ground version, works fine now that i did the BFC trick. nice and buzz saw like. i'm okay with the risk of oscilaltion, pos ground is a pain for me with 99% of everything i use being neg ground.

Fp-www.Tonepad.com · May 24, 2007, 03:45:32 AM

how FB is the capacitor you used?

Fp

Auke Haarsma · May 24, 2007, 04:32:19 AM

Quote from: Barcode80 on May 24, 2007, 02:14:38 AM
pos ground is a pain for me with 99% of everything i use being neg ground.

Why don't you put RG's +9/-9 V from one batt trick into the FF circuit? It's 1 chip, 2 caps and you have pos ground from a 'normal' adapter, which you then still can use with your neg-ground pedals. Coincidentally it is exactly what I have on my breadboard. I built RG's circuit and to test it build a FF. It sounds wonderful!

See: http://geofex.com/circuits/+9_to_-9.htm

MartyMart · May 24, 2007, 04:51:59 AM

The only success that I've had with this, is to turn the FF into an NPN Ge version.
Reversing power supply and all caps etc, this becomes a "proper" negative ground version
just like Fuzz centrals "Range Blaster" conversion of a Range master.

Trying this but keeping PNP trannies is 95% of the time a NO-NO !
MM.

aron · May 24, 2007, 05:19:35 AM

The warning is in the FAQ. I made even more of a warning.

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Tonepad Fuzz Face....im going crazy