Charge pump and PNP/NPN question

Meteorman

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First of all, let's be clear, I'm an electronic bumbler.
Have built a couple tube amps and a couple pedal kits.
Now working on a Fuzzface, using the PCB from Aion, the Solaris version.
Documentation says "There is also a charge pump allowing for -9V operation from a normal +9V supply".
The schematic shows a center positive 9V supply.
The pedal is PNP germanium based, which, as far as my noob-ness to transistors tells me, requires a certain polarity.
Does the charge pump affect this requirement ?
Does the presence of the charge pump mean that I could run NPN silicon transistors, without "reversing" the polarity of the circuit (turning e-caps around, etc)?
thanks for any guidance.
Aion's schematic:
upload_2021-11-11_15-51-8.png
 

Bendyha

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The charge pump is inverting the power supply, meaning you can run it from the same 9V supply as all your other pedals. The input transistor, Q3 is being fed from the non-inverted power supply, with the ground being negative to the supply, whereas Q1 & Q2 although using the common ground, they see it as being positive to their supply, as they need it.
Can you just swap out other transistors into positions Q1 & Q2...without changing things around, only if they are PNP.
But you do have a positive supply in front of the pump, so I guess you could add a switching matrix to have the choice of NPN or PNP, but as you note, the caps would have to turn as well, so it would not be an easy switching arrangement, but possible. Probably using non-polarized caps (or two back to back) would make things a bit simpler.
 
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Meteorman

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Biasing is different for silicon and germanium. Germanium usually is self biasing.

See this page for more info...http://www.hawestv.com/transistorize/germanium6.htm

With the exception of C8-10, The other electrolytics can be bi-polar.

appreciate the link ! Will give it a read.
This circuit has a trimpot for each transistor, so hoping that provides some biasing flexibility.
I omitted the “pickup sim” part of the circuit - this will be first in the chain.
 

cherryburst1

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I don't think so. Going from Ge to Si, you will need to add Rb. Click the buttons for Ge with no base resistor, then click the Silicon version next to it. If you use old school PNP transistors, the values shown on that website should be a good place to start....I have seen circuits work properly with less than .7 volts B>E, but not down to the levels encountered with no base biasing resistor added.
 

LightningPhil

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The charge pump is a neat little thing, quite small and inexpensive. But there's a bigger, better and more expensive alternative. Miniture isolated DC to DC converters. They can often be fed with a wide supply range and spit out a dual supply. The 1kV or so of isolation is pretty good at eliminating ground loops too.

I use similar devices for powering USB audio equipment where hum would otherwise sneak in. Normal wall adapters are generally a bit rubbish, but being followed up by one of these does the trick:
https://www.ebay.co.uk/itm/184440645025

They're less expensive if ordered from China.
 

AAT65

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yessir. Given the availability of ge vs si, was just wondering if si was an option. Guess not.
You can get plenty of silicon PNP (or NPN) transistors. As a couple of others have noted however you’d have to redesign to take into account the biasing and base resistance differences when you move from Ge to Si.
 




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