el85 tubes

[gary]

has anyone tried / seen these in a push pull cathode-biased output stage?
I'm trying to get some advice about bias resistor and transformer requirements.

Thanks

[Tillydog]

The datasheet contains the bare bones push-pull characteristics:

http://www.r-type.org/pdfs/el85.pdf

12K anode to anode impedance;
310R shared cathode resistor;

Gives 6.8W from 250V B+

Needs a bit more drive than an EL84.

Never tried it though....

[gary]

so, am I correct in assuming I can put the speaker on the next lower tap for these and be reasonably in the ballpark? i.e a typical transformer for an el84 18w amp.

[Tillydog]

so, am I correct in assuming I can put the speaker on the next lower tap for these and be reasonably in the ballpark? i.e a typical transformer for an el84 18w amp.

Should be. If you put an 8 ohm speaker on the 4 ohm tap of a 6k:4 transformer, it should look like 12K transformer.