need a little help with output stage design...

[riscado]

let's say I'm trying to run a pair of 6V6's (which will get me at most 12w) in ultralinear mode and I want to run them true class A (like an alessandro amp)... the amp is cathode biased!

From what I understand tubes work linear this way, so I can run the amp at maximum plate dissipation, right?

So the maximum plate dissipation for a pair of 6V6's is 12w, and I have around 360V in the plates and a 8k primary transformer (running ultralinear)... so I'm now missing the idle current value and the , but how do I determine the resistor value of the cathode?

any help please

thanks

[jurgen]

here's an example

http://www.mif.pg.gda.pl/homepages/fran ... 6V6GTA.pdf

[lastwinj]

360v is going to be a little high for class A ultralinear, IIRC. but hey, its all about the tone.

germ

[riscado]

Yes it's probably too high, that's why I'd like some help with the math involved!

[Ears]

Yes it's probably too high, that's why I'd like some help with the math involved!

From a well-known book, for class A tetrode connected, I'm unsure of Ultralinear connection as I expect the screen dissipation might have to be examined. And how the author arrives at bias range being the sqroot of Va is a little unclear to me. I expect you may want to tweek Rk or allow for trim to adjust Ia in any case.

Class A push pull, Rk unbypassed.
Va = Anode voltage, Pa = Max Anode dissipation

Peak Power = 2 x Pa

Average Power(or RMS if you must use the expression), Pout = Pa

DC idle current, Idc= (2 x Pa)/Va

DC Input power, Pdc= 2 x Pa

Peak plate current, Ipk= Idc x (sqroot2)

Peak load voltage, Vpk = Va/(root2)

Raa = (Va squared)/Pa

bias range Vb = sqrootVa

Rk (total) = Vb/Idc