JBorg wrote:

You believed that SS op-amp seems to be going strong after 30 yrs
while 6L6 tubes, otoh, are stuck in this "time warp" and so cannot
be significantly improve

You got it the wrong way round.

The 6L6 cannot be meaningfully improved because the sciencce of thermionics
hasn't changed since it was designed.

Hence it it 'stuck in a time warp'.

Not "it is stuck and in time warp therefore it can't be improved" as your
trying to suggest I said. In your criticism you have reversed the cause and
effect I referred to.

In terms of audio sound, if semiconductor are being improve all the
time to make them sound better, why are they being improve all the time
to make them sound better?

Semiconductors are being continually improved due to advances in solid state
physics. In short - the answer is 'because we can'.

That doesn't make older products *wrong* but it does make it a little easier
to design 'good circuits' ( trying to keep it simple here ) with the latest
parts.

Graham