In a message dated 97-02-27 01:28:13 EST, w6frmarv@juno.com (marv h. gonsior)
writes:
<< I would wonder if
the interelectrode capacitance was the same with the tube that "sounded
better!" Was its lead inductance the same and did it drive the same as
the reflected load to the exciter was possibly different, resulting in
greater IMD of the exciter itself, not the tube alone! In other words,
I would have some very serious reservations about "sounds," hi!
>>
Marv,
I know a little more about that article than usual, the author was contacting
me during writing of the article.
One of his claims was that a bias shift of a few volts from the nominal
voltage of 7.5 volts could produce "crisper" audio, another was that as soon
as a tube started being used audio quality went down hill fast. He said only
FRESH tubes sound crisp and stated he changes tubes long before output power
drops to maintain that crisp sound.
The author based his conclusions on over the air reports. He received more
good audio reports from random contacts AFTER he made his changes. I find the
conclusion remarkable since the exciter he used in the test had about five to
ten times the IMD level of the PA, and the reports were "by ear" only.
73 Tom
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