Reversed transistors, replacing NPN with PNP and vice versa........?

[frequencycentral]

The recent thread about the Death by Audio Fuzz War peaked my curiosity about reversed transistors, so I popped the (socketed) PNP output transistor of my Phase 180 and replaced it with a NPN to see for myself, putting the collector where the emitter should be etc. All good, it worked fine.

So it got me thinking - what are pros and cons? Take the legendary Ge FF for example, PNP, positive ground. What if you build it as a NPN negative ground circuit and just flip the PNP trannies? An advantage would be that it would play nice with power supplies powering multiple negative ground pedals.

I can't be the first person this has occured to, and there must be disadvantages, or we'd all be building Ge PNP FF's that way.

So what's the rub? And.....is there any application where it might actually give an advantage to use a flipped PNP in place of a NPN? Or vice versa?

[MikeH]

I'm sure RG will have a landslide of info on this-

On the FF- many people build them neg ground by using NPN trannys and flipping the electrolytes, but often high pitched ocillations and motorboating can occur.  RG advises against this.

[edvard]

I used to do that all the time when I was breadboarding FF's in reverse (didn't understand the concept of negative Vcc) and never could understand why I usually got an awful lot of background whistle without shorting base-collector with a ~100pf cap. That's why I never boxed a FuzzFace until I salvaged a couple of Ge 2SB175's and 324's and just stuck with the original.

To get around the grounding issue with PNP circuits, I just connect the negatives to ground even though that's the Vcc for the effect.
Haven't had a problem with them yet...

I noticed with the Differential Distortion circuit, I got a LOT less volume out of it when I flipped the circuit for NPN and never figured out why, so my latest attempt at that one is going to stay PNP.