Cold Cathode

[Joe Davisson]

Ice Cold.
http://www.analogalchemy.com/pedals/coldcathode.html

-Joe

[Peter Snowberg]

                           

:twisted:

I came up with almost exactly the same circuit without the now (TM) Joe Davisson in-line diode setup a while back and I thought it sounded good enough to be a commercial offering. If you add a switch for swapping the output to either stage 2 or 3 you can get some extra voice options with less overdrive.

Now to rebuild it with the diodes.

Awesome Joe!

Take care,
-Peter

[Lonestarjohnny]

Kewl, got my Fav J-Fets in the Circuit, I'm gonna have to try this 1 Joe,
JD

[Gringo]

Hi joe, thanks again for sharing with us.

Have you tried it with different fets? How would it react when using lower gain fets?

Thanks in advance.

[WGTP]

Joe, could you give us your release schedule for this stuff.  I was just getting ready to put a Vulcan in a box, but now I will have to try this first.

Thanks for all the goodies.  

[Jason Stout]

Cool Joe! I need to try the "diode compression" some time soon!

For everyone else, check this link as well.
http://members.tripod.com/~gabevee/sstubepre.html

[Marcos - Munky]

Cool, Joe. Thanks for another circuit.

[Joe Davisson]

The actual JFET type might not matter much, since the only attributes being used are the high-impedance and tube-like biasing.

I called it the cold-cathode to imply that it's a tube emulator, in terms of biasing and sound. The Vulcan got the sound but lacked sensitivity, which can be good or bad depending on what you want. I would say the CC circuit is better for solos, while the Vulcan is a "classic" high-gain sound.

The "middle" biasing for the diode/BJT is kinda neat because it lets you tweak the overall gain of the stage. A darlington can be used to emulate the high gain of a pentode, this worked out pretty nicely in a test I did. This was a Class-A amp using this "faux pentode", which sounded better to me than a MOSFET and was almost as loud.

So you can emulate different tube gains without touching the 1M input bias resistor, which is an important trait of the circuit. This should prove useful in re-creating preamp circuits.

-Joe