Is it possible to adapt kt88 to a 6A3 single ended

Rleff,Yes,I did pay attention to those wild guesses.

10-20-15: Charles1dad
A word to the wise is sufficient.

One would think so, Charles, but evidently not in this case.

Realdeal, in addition to the architectural differences I cited between the two tubes, with one being a directly heated triode and the other being an indirectly heated beam power tetrode (sometimes referred to as a beam power pentode), you might examine and compare the numbers in the datasheets for the two tubes. Which I did before posting.

You might consider, for example, the numbers for filament current, transconductance, plate resistance, and typical operating voltages and currents for the plates and grid(s) of each tube, among other numbers. As well as the graphs that will be included in a comprehensive datasheet.

Wild guesses? Yes, I did make a couple. In addition to guessing that the result of the substitution would likely be worse than poor sonics, I optimistically made a wild guess that depending on the design of the specific amplifier the result may very well NOT be smoke and fire.

Good luck.
-- Al

Hi Realdeal,
Al's very thorough and thoughtful response is based purely on technical considerations. I feel he is giving you very wise advice, if you want to proceed with this experiment of course you are free to do so. In my opinion these two tubes are about as different as one could imagine. If you do decide to continue this experiment let us all know how it turns out. The analogy would be comparing a Harley Davidson motorcycle to a Dodge Caravan minivan, they're just simply different.
Best of luck,
Charles,

Ignore Almarg. Wire it up as you see fit and flip the power switch. Just be sure to stand behind a 2" lexan shield and have a fire extinguisher ready. And whatever you do don't alert you insurance carrier.

Realdeal what would you do if ralph from atmasphere pops in on this thread and echo's Al's response?
I feel Al, Ralph and a few others are extremely well versed in electronic theory and application; their advice is solid.