Prune wrote in
:

I should have mentioned what I'm driving: plasma. Class A is not at all
inefficient in my application, as the bias power is not wasted but goes
into maintaining the plasma. So it's essentially an AF modulated plasma
driver. I know Hill's Plasmatronic speakers from the late 70s use that
mode of operation, but I'm doing it with air plasma instead of having to
use a helium tank. The V-I characteristic of the glow discharge is such
that voltage varies very little with current in the range that matters,
so essentially I need a 2-3 kV tansconductance amplifier. As few of
Hill's creations exist, I haven't found anyone with a circuit diagram
yet, and the patent doesn't give details of the amplifier, concentrating
instead on the plasma parameters. I know he used 6MJ6 tubes, but that
won't work in my case since I'm using air and need higher voltage. It's
single ended since the down swing of the sound wave depends on the plasma
thermal relaxation constant and is not really independent of the
amplifier.


I read somewhere that the cheaper Svetlana 4CX800A can be used as a
substitute for the Eimac 3CX800A7. Does anyone know if the Svetlana
tube also uses beam forming? Would I notice a difference at audio
frequencies? (I'm serious)
Also, can this tube be used in class A? On Eimac's site, it says it's
designed for class B, but does that mean that it merely won't be as
efficient in class A, or it will blow up, or what?