PSE UL EL84 or 6V6 or EL34?

[AudioGeek]

Looking to do something like this:

parallel SE UL connected output. 20-30W or so.

Haven't decided what output tube to use yet... so needing some input?

driver stage? dunno either... maybe pentode with global feedback.

can anyone give me direction on operating points for S/E UL for the above tubes?

Thanks!!

[Tubes4e4]

Hi Richard,

can anyone give me direction on operating points for S/E UL for the above tubes?

The problem is, that for SEUL you cannot use the UL op points as suggested for PP/UL in the data sheets, since those usually are given for class AB operation.

For SEUL, you really have to look at UL op plate curves for the tubes yourself and to chose a pure class A point.

UL op plate curves are a bit scarce anyway, especially for lowish plate/screen voltages which are better suited for class A op. And usually there is not much info given on the behaviour at higher (more positive) plate swing, since for class AB this would go into the cutoff region anyway.

But you can measure UL curve sets suitable for class A yourself, given you have a suitable PSU und DVMs. It isn´t that hard, I have done this several times.

Tom

[AudioGeek]

does anyone have the curves for these tubes, or can point me to where i can find them?

or have a general idea of where i can run them at?

out of el84, el34, 6v6 which one would work "better" as a UL connection?

txs!

[tubelab.com]

If you want 20 watts you will need a lot of EL-84's in parallel. I think with EL-34's you are going to need 3. Look at this circuit.

http://www.lundahl.se/pdfs/claus_byr...ifier_8wse.pdf

The text explians a lot. I have seen UL curves for the EL-34 somewhere, perhaps the original Mullard data sheet. I am currently at work , so I don't have it here.

[Andrewbee]

here is an idea

look here
Andrew

[Tubes4e4]

Originally posted by AudioGeek
does anyone have the curves for these tubes, or can point me to where i can find them?

For EL34 and several similar power class others, have a look at the Sofia tracer site

For 6V6, you probably will not find any UL curves. Maybe you will have better luck with EL84, just browse through the EL84 data sheets available at Frank´s

Again, even if you find UL curves, they probably are not suitable for SEUL class A.

Tom

[richwalters]

As tubelab mentions....... parallel pairs EL84........this config in true pentode will hull out 30W with 3K6 a-a Z in fixed bias with B+ around 300V, an advantage as the optimum load resistance is way lower than if pair of EL34's were used. The emphasis is then on a good power supply.
I'd thought about this for MI. The low B+ makes a c/o switch quite feasible from UL to pentode operation.
I'm seriously considering using triple p-pairs which makes things even more attractive around the 50W park.

richj