Which tube? How much power can it produce?

[flysig]

How much power can an output tube put out? Can an inference be made from the Wa spec, or is there some other way of gleening what the intended output power is?

I'm looking for in-production output tubes for a 1W to 5W design. How do I judge the different offerings? Once there are several candidates I am happy to start drawing load lines and crunching numbers.

I haven't decided yet if it will be SE or PP.

 

[SY]

I haven't decided yet if it will be SE or PP.

Well, you better start there!

Figure a good 4:1 minimum power difference between SE and PP. Assume SE to be no more efficient than 25%, so the minimum Pd will need to be 20-25W.

For P-P, there's a host of small tubes that will give you what you want; your next decision will be DHT versus indirectly heated, triode versus pentode versus ultralinear.

Your speaker choice will dictate what direction would have the best set of tradeoffs for you.

 

[Jeb-D.]

This is always what I go by for approximation

Class A Triode: Pout = %25 of tube(s) total Pmax rating.
Class A Pentode: Pout = %50 of tubes(s) total Pmax rating.

Class AB1 Triode: Pout = %50 of tube(s) total Pmax rating.
Class AB1 Pentode: Pout = %100 of tubes(s) Pmax rating.

So for example, if you want a 5W amplifier here are your possibilities.
20W-plate, rated Triode in single-ended
10W-plate, rated Pentode in Single ended
A pair of 10W- plate, rated triodes in class A PP
A pair of 5W-plate, rated Pentodes class A PP
A pair of 5W- plate, rated triodes in class AB1 PP
A pair of 2.5W-plate, rated Pentodes class AB1 PP

Of course for class AB there is a fairly large Pout range that can be had, but the way I approach the topology it usually gives those numbers.

For Ultra-linear, the output power can substantially range depending on design. Usually it's between %70-%100 of it's Pentode equivalent.

 

[flysig]

Thanks! Those rules of thumb are just the starting place I needed.