[Top] [All Lists] Re: [AMPS] >3-500Z Biz

To: <>
Subject: Re: [AMPS] >3-500Z Biz
From: (marv h. gonsior)
Date: Thu, 27 Feb 1997 17:26:55 PST
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Subject: Re: [AMPS] >3-500Z Biz
To: <>
Date: Thu, 27 Feb 1997 18:47:12 -0500 (EST)
Message-ID: <>

In a message dated 97-02-27 01:28:13 EST, (marv h.

<<  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!

I know a little more about that article than usual, the author was
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
FRESH tubes sound crisp and stated he changes tubes long before output
drops to maintain that crisp sound.

The author based his conclusions on over the air reports. He received
good audio reports from random contacts AFTER he made his changes. I find
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

Hello Tom,

VERY INTERESTING!  I can see all sorts of variations occurring from the
data you've provided.  For example, the relative gain of each tube, old or new 
etc. would give rise to a different Ipq resulting is a bias shift as the 50 
watt zeners are really a relatively poor regulator for best
linearity.  This could result in a new Ipq that could result in a more
or less favorable IMD; e.g., more or less cross over distortion.  Gosh,
he sure must have gone thru a lots of cash, changing out those tubes
while, if I am correct, all he had to do is replace the zener diode!  I
could also speculate on the relative match between the two tubes etc.
etc........far far into the night, hi!  Your final input, relative to
the IMD of the exciter, really takes the proverbial cake!  Thanks for
your informative insight into that report.


Marv, W6FR

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