[John Jensen]

I've got a pair of 6550 amplifiers that are in need of a replacement set of
output tubes. The current set of =C= 6550s (by way of Ned Carlson) have a
couple of tubes falling off in emission causing balancing problems. What is
the current opinion of the 'best' of what is in current production regarding
AQ, robustness, etc? I am sure I will get a lot of differing opinions.

Thanks,

John

P.S. These are in a pair of amplifiers lovingly hand-built over the winter
of 1959-1960. The design is the Herbert Keroes Acrosound 60W Ultra-Linear
Williamson (but with Dyna 431 transformers). Still going strong.