Just got interested in Fuzz Faces and decided to bread board the circuit to swap in/out several PNP Germs to try and get a feel for which ones sound best together. I used the geofx leakage/gain circuit to rate them. (keeping ONLY those that had acceptable leakage rates AND gains between 80-130)
I have read all of the literature that I could find however, I am still curious as to how I can determine what the BEST resistor values are for the PNPs. I know that Steve over at smallbear sends out specific resistors for the Fuzz circuit when you order pairs of transistors. I assume that he does it by ear but what do I need to listen for for which resistor value?
Also, when I was plugging in PNPs to my circuit, I tried to keep Q1 at around 80-90 gain, and Q2 at 100-120. It seemed that every combination I used had break up in the sustained notes/chords. Faster break up with the higher notes.
Just looking for some good info on how to get this circuit sounding as best I can.
P.S. Here is the circuit that I breadboarded from: http://www.generalguitargadgets.com/pdf/ggg_ff5_sc_pnp.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
I didnt add the optional items OR the LED circuit. I used 1% resistors for R2 and R3. I used carbon comps for R4 and R5. Aluminum electros for C1 and C3. Finally, I used Poly for C3.
Thanks for helping.. ;D
I think it's best to replace the bias resistors with trimpots in series with a small value resistor, in order to be able to tweak the bias as necessary. Replace at least one of them, I replaced the 33k with a 50k trimmer and a small resistor, and the 8.2k resistor I'm putting an external 10k pot with a resistor. This way, you can tweak it to deal with the variations in PNP germanium value and the changes in sound that come from temperature variations (germaniums are very temp-sensitive).
Al
Or just socket the transistors and swap them until you find a combination you like.
If you're going for an authentic germanium Fuzz Face tone you might want to try even lower gain transistors. The original NKTs usually had hfes between 30 and 90.
I also got my hands on some SWEET 2N388 npn germanium transistors but they have gains of 150 and 175 :o
I am hoping that even with the high gains that they will work so I can have an NPN germ fuzz!
of course they will work. Arbiter used much higher gain transistors in the silicon verison.
I'm using the 60's version with russian transistors, like it alot with my cheap squier strat with single coils.
What ''perfbread'' is perfect for...
Sockets, trimpots, or just 'leggy' resistors that can be soldered to between the top of the perfboard and the resistor body, start with 'the large value' then use a pot [with testclips] or just solder the resistor across the resistor for the lower values.
Generally speaking it's a ballpark type deal, and 'optimum' FF bias would almost be worth mention except it's always different, and peoples druthers vary too.
Reminds me of an .049 engine, one sounded different than the next, with different max RPM and starting procedures, the mixture settings always required 'finding' in order to make best use of the glowplug [ie get it glowing/started before the coil burns up]...which also varied in lifespan depending on the engine it was in.
Get it up and running, open it up as best possible...on to the next was my summary, then compare the two 'engines' after they're both set up to get a better idea of what 'optimum' is.
That said, any one of the .049's only varied a little bit after break-in anyway, any one of them had enough power for the vehicle frames I put them in, mostly just teh starting procedures varied.
>Reminds me of an .049 engine
I loved the Tee Dee.
Quote from: Govmnt_Lacky on December 24, 2010, 11:48:25 AM
I also got my hands on some SWEET 2N388 npn germanium transistors but they have gains of 150 and 175 :o
I am hoping that even with the high gains that they will work so I can have an NPN germ fuzz!
You can also try putting small resistors at their emitter to lower the inherent gain. Like maybe 47-100 ohms.