Turning Positive Ground into Negative Ground

[Triffid]

There are quite a few older effects that are wired up with a positive ground, now I know for common ac adapter compliance it is nicer to have negative ground.   I was looking at the difference between the PNP Negative ground and PNP Positive ground versions of the Fuzz Face @ general guitar gadgets and it looks like to turn a Positive Ground into a Negative Ground you...

1) turn ground connections into+9V connections
2) turn old -9V connections into ground connections
3) reverse your capacitor polarities

Is it as easy as that?

[smoguzbenjamin]

And change PNP trannies to NPN and vice versa. For the rest, yes that's it I think.

[Triffid]

Hmm... General Guitar Gadgets have PNP versions of both postive and negative grounded Fuzz Faces... do you really have to turn PNP into NPN?

*edit* Here are the links
Negative Ground: http://www.generalguitargadgets.com/v2/diagrams/fuzzface_sc_pn.gif
Positive Ground: http://www.generalguitargadgets.com/v2/diagrams/fuzzface_sc_pp.gif

[smoguzbenjamin]

I think so. It makes sense to do that in my head. At least my intuition is screaming at me that that's right but I have absolutely nothing to back it up with :|

[petemoore]

And converted it to whatever the [npn or npn] transistors he was using.
 We went through some contortions for about a week, then when converted npn/pnp to npn/npn [Actually I forget the transistor type], the circuit FF bagen functioning, and he was quite haappy!!!
 I don't remember any reason or resolution for such a thing...I would recommend using your transistor type in a circuit of that type [npn OR pnp] since both circuits and both type transistors are available.
 The DC blocking caps work fine as long as you don't try to connect opposite ckt. grounds... ie pos and neg ground ckt on the same supply rails.

[Chico]

See the article "PNP Power" on the AMZ site.  Jack covers this topic quite nicely.

Good luck

[Triffid]

Hmm, sorry Chico... I am having a hard time locating that article, can you post a link to it?

Thanks

[bwanasonic]

The topic is covered at both GGG and AMZ, but in practice, most accounts are PNP+ neg. ground = headaches, usually in the form of strange oscillations. It should be possible in theory, but many people find it is more trouble than it's worth. In the case of the Ge Fuzz Face and Ge Rangemaster, these effects have insanely long battery life, so building them PNP/ Pos. gnd. / Sans adapter is not much of a problem.

Kerry M

[spongebob]

A word of warning: Make sure you change *all* ground connections, otherwise you will short your battery :mrgreen:

I'm telling this because it happened to me, and I almost blew up the battery because I didn't notice immediately what was wrong.

Lesson learned: I now check the resistance between the battery clip connectors on every new circuit before the battery is attached!