Sander deWaal wrote:


"Michael McKelvy" said:

But they aren't, with good reason. The momomet you start running current
through a tube it is degrading.

Actually, after a hundred hours, the parameters of most tubes remain
pretty stable, to sink only when the end is near, like a NiCd battery.
With preamp tubes, usable life span can be 10,000 hrs or more, with
good (mostly NOS) power tubes it can be in excess of 5000 hrs.

In a McIntosh or Quad II the tubes have an easy life, they're biased
near class B.

--
Sander de Waal
" SOA of a KT88? Sufficient. "


Sander's statements of *fact* are certainly refreshing and in marked contrast
to the anti-tube baloney pedaled as OSAF attempted by McKelvy. Sander was too
much of a gentleman to say "prove it" to the propagandist.

Another pragmatic question is that even when the tubes start losing some of
their original effectiveness, does this result in *audible* degradation of the
sound in terms of listener judgment - as opposed to purely instrument-based
measurements, per se, that don't necessarily correlate well with listener
perceptions. I realize this may be more problematic for output tubes, but even
in that case, would this not also depend upon (a) listening levels routinely
used, and (b) sensitivity of the speakers involved?



Bruce J. Richman