NPN and PNP? Why bother?

[mattpocket]

So, most normal effects are negative ground right?

When we use these types of tranny's that are PNP we have to have a positive ground circuit. Which is a pain in the ass for powering your effects. Why bother building a PNP fuzz face when you can build a NPN one?

Matt

[tcobretti]

Most old Ge transistors are PNP.

[jlullo]

the biggest reason that i see is that there are many PNP Ge trannys available, but not so many NPN.  You could always get into silicone, but i think a lot of us here love the idea of playing with Ge

I've bought a bunch of germanium transistors off of ebay, and i keep hoping to find more NPN available, but somehow i've ended up with a stockpile of PNP!

[mattpocket]

is there a simple circuit to add on to your effect so you could use a negative ground power supply, but then switch it somehow to positive?

forgive me if that is a completely stupid question, I am in somewhat of a deep-end with regards to learning about electronics theory. The learning curve has been huge so far... the more I learn, the easier it becomes to understand something new.

Thanks

[jlullo]

i'm not sure if there is a simple circuit, but you can just flip the polarized caps and battery polarity for converting a PNP circuit to NPN (with PNP transistors of course).  However, you're going to have to cross your fingers and your toes that you won't get the dreaded motorboating effect.

I've never done it myself, but there are people here who have, and do often.

[Dragonfly]

is there a simple circuit to add on to your effect so you could use a negative ground power supply, but then switch it somehow to positive?

forgive me if that is a completely stupid question, I am in somewhat of a deep-end with regards to learning about electronics theory. The learning curve has been huge so far... the more I learn, the easier it becomes to understand something new.

Thanks

You could use a MAX1044 to flip polarity, IIRC...

AC

[Seljer]

is there a simple circuit to add on to your effect so you could use a negative ground power supply, but then switch it somehow to positive?

forgive me if that is a completely stupid question, I am in somewhat of a deep-end with regards to learning about electronics theory. The learning curve has been huge so far... the more I learn, the easier it becomes to understand something new.

Thanks

you can wire it the wrong way round but many people have reported motorboating, noise and other bad things (go look and the PNP fuzz face - negative ground and postive ground on generalguitargadets)
though I guess you could use on of those MAX1044 things to turn +9V into -9V, it kind of seems overkill, I just live with a battery (even if you leave it plugged in, it should last a couple of months), or you could get ahold of some NPN germanium transistors....or just work with silicon transistors instead

[petemoore]

Why bother building a PNP fuzz face when you can build a NPN one?
 Indeed. I have no Pos Gnd FF or other circuits.
 To see what a PNP sounds like compared to an NPN...which isn't really ever a fair test...I think you'd have to build a batch of both to 'barometer' them because every FF tends to sound different, especially if there's any Ge in it.
 

[zachomega]

I prefer positive grounding.  It makes a lot more sense and as a lot of guys have noted, most old germanium parts are pnp and any new parts that are npn typically have a pnp counterpart. 

Additionally, in the rare case of a bad coupling cap on the output of an effect, the amp will see a negative voltage which in a tube amp is a hell of a lot safer than it getting a positive voltage on the grid of the first stage. 

-Zach Omega

[Barcode80]

there is always the argument that if we are duplicating certain vintage circuits (as is the case often) then the available schems are all pos. ground. which is worth more effort, redrawing a neg. ground schem and/or flipping parts or just reversing the leads of a battery?

I myself agree that positive ground seems a tad pointless given that almost all pedal board power supplies are neg. ground and i don't use batteries, but there is no reason to reinvent the wheel if you don't need to.

[aron]

Here is an article that you should check out:

http://www.muzique.com/lab/fuzzface.htm

[dachshund]

If you want the GE sound, PNP is a lot more practical from the perspective of buying transistors with known Gain or hfe. It seems that the inventory of NPN GE is so limited that you're on your own buying and testing for hfe. That can get expensive.
At least that's my impression, please correct me if I'm wrong...