using NPN instead of PNP in fuzz

[lcipher3]

So looking at all the cool fuzz projects and a lot are PNP - not all but a lot. Given that I've recently inherited a bunch of NOS NPN germaniums I was wondering....
Anything wrong with - aside from not being correct vintage wise - using NPN and jumping / leaving out the charge pump that is used to give -9VDC?
Seems the circuit would be identical / work with NPN just fine powered by +9VDC?

 

[Chas Grant]

I’ve done this a few times. Just make sure you reverse the electrolytic caps. If the PCBs is marked for PNP transistors then you will need to put the negative lead of the caps in the square pad, also make sure the power is connected correctly. If looking at a PNP schematic, the ground will be the+9V for NPN . Also check the gain of the transistors, Small Bear Electronics has a nice article on calculating the hfe of germanium transistors that works well for NPNs also!

 

[Chuck D. Bones]

Ha, ya beat me Chas!

These "cool fuzz projects" are tone benders, fuzz faces & their derivatives, yes? Those circuits are all sensitive to hfe and leakage. Some germanium circuits depend on leakage to function. Your best bet is to socket the transistors and try them. The 2N1306-2N1309 that I have are all low leakage and as such are unsuitable for pedals such as the ZonkBox, Tone Vendor Mk I, etc.

 

[Nostradoomus]

Yep, flip your electro caps around, leave out the charge pump but jump pads 1-5, ignore the 10uf cap from pads 2-4 in the charge pump circuit as it is of no use to you now!

 

[lcipher3]

Thanks - yeah I just measured all my 1960's Texas Instrument 2N1304/6 stash and I have a pretty good selection to chose. And AionElectronics has some decent guides on gain and leakage, as well as biasing- I know the tone benders can be picky. I'll probably order a few PNP fuzzes and try them out - sort of HAVE to since I have the NPNs laying around homeless. Although the best may be the Fuchsia and its NPN anyway

 

[Chas Grant]

Ii just went through a very similar situation. Landed 30 unbranded untested germanium transistors For free! Had a nice mix of PNP and NPNs. Built a PNP for my daughter from scratch without using a trim pot. I breadboarded the circuit and switched out the resistors until I got the bias voltages right for Q1 and Q2. It sounds great! I compared it to a previous one I built with a matched set, this one sounded just as good as the matched set! Did the same thing for the NPN and it sounds great also! I really didn’t need another fuzz pedal but they are a lot of fun and each one takes on a life of it own!

 

[Chas Grant]

Ha, ya beat me Chas!

These "cool fuzz projects" are tone benders, fuzz faces & their derivatives, yes? Those circuits are all sensitive to hfe and leakage. Some germanium circuits depend on leakage to function. Your best bet is to socket the transistors and try them. The 2N1306-2N1309 that I have are all low leakage and as such are unsuitable for pedals such as the ZonkBox, Tone Vendor Mk I, etc.

Ha, ya beat me Chas!

These "cool fuzz projects" are tone benders, fuzz faces & their derivatives, yes? Those circuits are all sensitive to hfe and leakage. Some germanium circuits depend on leakage to function. Your best bet is to socket the transistors and try them. The 2N1306-2N1309 that I have are all low leakage and as such are unsuitable for pedals such as the ZonkBox, Tone Vendor Mk I, etc.

Sport about that!???

I Love a good Fuzz pedal though!!

 

[lcipher3]

Im starting to see why people get sucked into the whole fuzz pedal black hole! It's a simple enough circuit - but there's a lot of variation that leads to all sorts of experimentation and fun. Very organic... kinda like cooking or gardening...

 

[Chas Grant]

Im starting to see why people get sucked into the whole fuzz pedal black hole! It's a simple enough circuit - but there's a lot of variation that leads to all sorts of experimentation and fun. Very organic... kinda like cooking or gardening...

I totally agree It’s a great little circuit! If you have trim pots for biasing on both transistors you can use almost any transistors in it. Believe it or not, cheap ole 3906s don’t sound half bad in this circuit if biased right. I figured this out when I first started breadboarding?

 

[lcipher3]

I totally agree It’s a great little circuit! If you have trim pots for biasing on both transistors you can use almost any transistors in it. Believe it or not, cheap ole 3906s don’t sound half bad in this circuit if biased right. I figured this out when I first started breadboarding?

yeah I've got bucket full of the old metal can 2N2222 that I've heard can be used in some as well - univox super fuzz?

 

[caspercody]

Can you use 2N3906 in place of the (3) GE's called out in the BOM?

 

[Chuck D. Bones]

If the circuit is leakage-biased, then the answer is "no."

 

[caspercody]

Asking about using in the Zonkbox fuzz

 

[Chuck D. Bones]

In that case, the answer is "NO!"

This article should provide some insight into the workings of the Zonkbox, aka FZ-1.