NPN Fuzz Face Questions

[ringworm]

Hi there,
My first post and first build.
I'm trying to put together a Fuzz Face using the pcb at Tonepad. I have a pair of NPN BC109 transistors and was wondering, as the board is negative ground does that mean I can put NPN transistors in 'as is', without having to switch the polarity of the electrolytic capacitors or the power supply?
Cheers.

[jimbob]

correct.

[Drake120]

Well, from what I can tell (but I'm beginner also), no, 'cause tonepads version is prepared to use PNP trannies with negative ground...

Both of the Tonepads versions incorporate PNP transistors, there's only the trick with the jumper and a cap, as said here:
"In this layout the trick is in the jumper that connects circuit ground to the power supply. That jumper and the input cap are the only two parts that need changing in order to switch between the two ground schemes."

Well, to use NPN transistors, use schematic for POSITIVE ground version, just use +9V instead of -9V. Connect black battery wire where it says red wire and opposite. Place C1 as in the negative ground schematic.

But just what I can tell after looking at Tonepad.

(JD)^S

[ringworm]

Now I'm confused.
The positive ground version of the Tonepad FF has the polarity of the caps switched.
Guess I'll have to wire it up and see.

[petemoore]

  The emitter goes toward gnd.
  The caps - side needs to always be more - than the positive side, so if neg gnd. cap neg goes to or toward gnd.
  Start with the schematic and the data sheets, and notice the little arrow points the other way when comparing NPN to PNP...note how that little arrow, the polarity of the PS [and diodes...and capacitors [anything with polarity] changes when looking at a schematic.
  Two best examples of FF are:
  NPN Neg Gnd.
  PNP Pos Gnd.
  they both work great, pick one of these [check transistor stock first], then build.

[ringworm]

I understand the early FFs were all PNP and pos ground but i though since the Tonepad version had a neg ground schematic that NPNs could be used without having to switch the electrolytics. Do i have to switch the collector and emitter on the BC109s then? I'll take a look at the schematic and see what I can figure out.

[solderman]

You are correct in you're first post. listen to Jjimbob.

//Solderman

[Exactopposite]

as long as you are using a schematic for npn you should be in good shape.

[Drake120]

OK, sorry if I misled you. But there's sth I don't understand now. Why Tonepad's layout claim for PNP trannies even in negative ground version? I found negative ground FF for NPN schemo there:

http://www.geocities.com/teleman28056/fuzz_face_schematics.html

So aren't the Tonepads's layout both prepared for PNPs? The schems there are different that the one above.

[ringworm]

"Why Tonepad's layout claim for PNP trannies even in negative ground version?"

Yes, this is the crux of my question, even though both the pos & neg ground schematics are designed for PNP, is the neg ground version usable for NPN without any adjustments, or if adjustments are needed what are they? Lots of conflicting information. Maybe it's me, i'm probably asking a daft question or not understanding something fundamental about the layout
Looking at the two geocite layouts the only difference between either is that the polarity of the power and the caps are reversed. Which just brings me back to my original question regarding the Tonepad neg ground FF.
Think I'll build the Tonepad neg ground version as is and see if it works.

[Drake120]

From what I understand, there are four possible versions of FF:

-PNP trannies, negative ground
-PNP trannies, pos ground
-NPNs, neg
-NPNs, pos

Tonepad holds first two versions, ringworm looks for a third one, I think. It will be weird if you could place NPNs in the circuit without any changes when the circuit is made for PNPs... But I maybe I missed sth.

[ringworm]

Yeah, it didn't work.