There is the KT150 under the Tung-Sol name, made in Russia. There are mixed reports on how it actually sounds but it is intended as an audio tube and not a transmitter tube.
http://www.tungsol.com/html/kt150-tung-sol.html
On Thursday, December 8, 2016 at 7:20:48 AM UTC-8, wrote:
What is the most powerful audio output tube, as far as RMS wattage
output?
I have gotten some powerful sound from four 6L6 tubes in push-pull
parallel. but I want more. I know it's possible to use eight 6L6 tubes,
which I believe is called " push-pull parallel - parallel", but I'm
looking into other possible tubes.
At one time, I thought the 807 tube was more powerful than the 6L6, but
after careful research, it's almost identical, but with a different
envelope (plate on the top cap).
I'm looking to get a full 500W RMS (or more) output (per channel), from
all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
RMS (per channel).