Clyde Slick wrote:

"Pooh Bear" wrote in message
...

The 6L6 ( or whatever ) is still around in its original form since it
isn't capable of being significantly improved. It's stuck in a time warp
so to speak.


It's still around in its original form because it doesn't
require any improvement.
Also, that somethjing is incapable of being improved
may be because it has reached its state of perfection.

I'm sure that some desirable scope for improvement must exist - gm linearity
perhaps.

The laws of physics ( specifically thermionics ) dictate the performance
however.

Graham