Tonepad Fuzz Face - Inverted Polarity Issue

[Slade]

Hi, everyone,

I'm making a Tonepad version of the famous Fuzz Face but I need it to be with negative ground like the standard to use it with a "normal" PS. The problem is that when I made the "jumper mod" to get negative ground I also get a "motorboat noise" when the sustain pot is almost at a half. Reading the build reports at tonepad I found a modification (from Urban Osterman) to get rid of this noise by simply adding a 100uF cap "using the holes for the neg-pos-ground jumper...".

So I want to know if someone has made this pedal with this modification and what have you did with the noise issue.

Thanks,

Slade.-

[brett]

Hi
the 100uF cap works very well in eliminating the motorboating problem.  Any large cap of good quality (low ESR) will do the trick, as it connects the supply and ground at frequencies from a few Hz up.
cheers

[Slade]

Thanks, brett,
I'll try that.
Have you did this before?

Greetings!

[R.G.]

Please go do a search on the inverted power supply problem.

I keep telling people - unless you really know what you're doing and are willing to take responsibility for reconverting back to positive ground don't use inverted (negative side) grounds on PNP pedals that used to use positive ground.

Many times you get away with it. Some times you don't, and nothing except reconversion to positive ground will make it work without noise or oscillation.  If you're not already pretty skilled at effects, save yourself some trouble and make it positive ground. The extra power supply is less expensive than the time and effort you can spend on debugging.

[Slade]

R.G., sorry for my topic, i know it's repeated day by day, I searched the forum after posting it, my mistake.
I know that the best way is not to invert polarity, I'm just looking for experience of people who have tried this before me. Again, I did the search after posting it. I really need to do it, not just a fit. I'll keep trying, if it works for me I'll let you know.
Thanks,
Greetings

[MikeH]

R.G. is totally right (as always) but sometimes you can get lucky (like I did) by putting a really big cap across the power supply.  I used 1000uf and it fixed the motorboat issue.

[R.G.]

R.G., sorry for my topic, i know it's repeated day by day, I searched the forum after posting it, my mistake.
I know that the best way is not to invert polarity, I'm just looking for experience of people who have tried this before me. Again, I did the search after posting it. I really need to do it, not just a fit. I'll keep trying, if it works for me I'll let you know.

No problem - I wasn't yelling at you, but I have to keep posting this because many, if not most of the conversions do work. But that's no help for the people who expect it to and run into the problem.

The simplest way to fix it is with a BFC, maybe 1000uF. If that doesn't do it, you can put a charge pump converter chip in the box, one 8 pin chip plus three capacitors, and make -9V out of +9V, and keep the same ground.

[Slade]

Thanks for your advice, R.G., I'll be trying this soon. I have thought about what you said before, but it's very difficult to find the chip here. Anyway, I'll do my best to get it. Thanks again,

Greetings.

[Mugshot]

R.G. is totally right (as always) but sometimes you can get lucky (like I did) by putting a really big cap across the power supply.  I used 1000uf and it fixed the motorboat issue.

ahm, when you say "add a big cap across the power supply", do you mean you add ANOTHER cap with the leads soldered to the + and - of the circuit?