push-pull class a 6l6, el34

[funkmeblue]

I am very interested in how george alessandro is able to use 6l6, kt66, and el34,s in his black and tan. 15 watts pure class A ultralinear. I don't want to clone this amp, just the output section. Any one know what plate voltages to aim for, what cathode resistor, output transformer inpedence, anything? thanks for your time

[Alexo]

Ha! I was just embarking on a push-pull class A 6L6 build, but I couldn't find the right power transformer and ended up going more class AB. All the data you need is in the datasheets, circuit examples and all. For 6L6's, you want 270 volts on the plates and screens, plus 17.5V cathode voltage means you need a B+ of about 290, I'd want a PT rated for at least 200ma.

The datasheets call for that cathode voltage with 145ma plate + screen current = 120 ohm cathode resistor.

All that plus a 5K OT should give you 17 or 18 watts class A.

Let me know if you find a good power transformer.

[Stanz]

to use 6l6, kt66, and el34,s in his black and tan. 15 watts pure class A ultralinear.

Wouldn't that make it a SE amp if you are using 6L6 and it is only putting out 15 watts seeing as how that is what you would expect from one tube? SE would make it class A for sure.

[funkmeblue]

not looking for single ended, push-pull class a ultralinear. Edcor makes a power transformer that is 180-0-180 250 ma 6.3- 3 amp. Would that get me close?

[Firestorm]

If George is only getting 15 watts out of two of the mentioned output tubes -- and with an ultralinear tap too -- he's got to be running the power amp at only about 250 volts. A 180 - 0 - 180 PT with a full-wave solid-state rectifier should get you right there.