NPN Tonebender MK III questions...

[Bill Mountain]

So...It only took me 10 years but I'm finally trying out a bunch of the hip old fuzz designs.  The tonebender mk III intrigues me because of tales of being a smoother sounding fuzz (is that true?).

I won't pretend to understand the reversed bias diode in the last gain stage but I do have a question about it.  If I were to switch this design to NPN (got some NTE NPN Ge trannies that don't sound half bad!) would I reverse the diode?

Also...this appears to be nothing more than a darlington pair overdriving a the Ge transistor at the end.  Am I missing something?  Is there some mojo I'm not seeing?  I could rig up all sorts of boost stages to overdrive all sorts of clipping stages but at what point am I no longer building a MK III?

[Govmnt_Lacky]

If I remember right.... the diode is Germanium and it is used for temperature stability so the transistor (Germ as well) does not wander too far. 

[Bill Mountain]

If I remember right.... the diode is Germanium and it is used for temperature stability so the transistor (Germ as well) does not wander too far. 

But would I reverse it if going NPN?

I wonder...If I put in an emitter resistor or C-B feedback resistor would I still need the diode?

[nocentelli]

slight tangent, but if you fancy trying out a mkIII-ish circuit, but without fretting about diodes or suitable Ge transistors, the DAM Greasebox 83 is worth a play on the breadboard.

[LucifersTrip]

If I remember right.... the diode is Germanium and it is used for temperature stability so the transistor (Germ as well) does not wander too far. 

But would I reverse it if going NPN?

yes....and yes, it's smoother than the MKI and MKII

I've built a bunch of different versions with different combos pushing the last stage and I could never get anything (yet) to sound as good as 2 germs up front (use low leakage, gain not needed to be high for that darlington pair).  The best sub I used for the pair was a single darlington, but that ge pair pumps out a fatter, softer tone. Take the signal right after the ge pair and you'll get a good overdrive.

[mac]

http://www.diystompboxes.com/smfforum/index.php?topic=104998.msg978554#msg978554

mac