madbeanpedals::forum

Projects => Tech Help - Etcher's Paradise => Topic started by: tatou on December 27, 2018, 10:23:33 PM

Title: NPN version of Zombii?
Post by: tatou on December 27, 2018, 10:23:33 PM
I'm considering building Zombii (Fuzz Factory variant):
http://madbeanpedals.com/EP/schematics/Zombii.gif

On hand, I have a few PNP silicons but I also have a pair of NOS NPN germaniums that have been gathering dust for a couple years. I feel like at one point I knew some tricks for adapting PNP circuits for NPN, but it's been too long. Anybody have any tips? It should be possible, right?
Title: Re: NPN version of Zombii?
Post by: timbo_93631 on December 29, 2018, 11:45:36 AM
Zombii is negative ground, the PNPs are being used in a clever way.  To use your NPNs youd have to flip the polarity if everything , use positive ground power and a PNP silicon in Q1.  Instead, consider sourcing some cheap 2n404s and build it with a lot less hassle.
Title: Re: NPN version of Zombii?
Post by: tatou on December 31, 2018, 02:04:24 PM
Thanks!

After a bit more research on the circuit I realized that it was negative ground, and I found some NPN schematics but they required positive ground! :) I breadboarded it up using some PNP silicons I had on hand and think it sounds pretty killer that way, so I'm going to go ahead and move forward with that. I'll socket the trannies and maybe might pick up some germaniums try out later.

Some other mods I made, in case anyone is interested:
* omitted the "fat" switch mod & C7 (10u).... it didn't sound pleasing with my setup
* changed "STAB" pot to 10kB
* added a "wonderfully stupid tone control" with a 100n cap at the end