> I was reading the Bill Orr handbook and on his section about
> amplifiers he says.....A properly designed grounded grid
> amplifier should produce 2 to 2.5 times the plate dissapation
> of the tube in output.
Depends on what Orr means by the statement ... if he means that
the output (amplifier + feed through power) will be at least
twice the power dissipated in the tube, he's probably accurate
at "two times." If he means that a tube should be capable of
producing 2.5 times its plate rated plate dissipation (e.g.,
1250 W in a 3-500Z or 3750 W in an 8877), he's mistaken or
worse.
For example an 8877 is rated for 1500 watts plate dissipation.
Even at maximum HV (4KV) and maximum current (1A) - Eimac
Absolute Maximum ratings - you will not see 3700 W output.
Eimac's own data sheet shows only about 2KW at 3500V/1A.
The calculations are similar for the 3CX800 - 2500V/.6A gives
about 900 Watts out based on the absolute maximum ratings. Even
with Eimac's own data showing 800 mA for "short term duty" 1370W
output is far less than 2X the 800W plate dissipation.
Absolute Maximum ratings for a single 3-500Z are 4000V/.4A
or 1600 W in. With 65% efficiency, the output is barely twice
the plate dissipation. Eimac's typical operating conditions -
3KV/.37A - shows 750W output or only 1.5 times rated plate
dissipation.
There may be tubes with lower rated plate dissipation that
can be driven harder but these three examples say that Orr
was over reaching with his statement.
73,
... Joe, W4TV
> -----Original Message-----
> From: amps-bounces@contesting.com
> [mailto:amps-bounces@contesting.com] On Behalf Of Gudguyham@aol.com
> Sent: Wednesday, July 23, 2008 12:30 PM
> To: amps@contesting.com
> Subject: [Amps] Bill Orr comment
>
>
> I was reading the Bill Orr handbook and on his section about
> amplifiers he
> says.....A properly designed grounded grid amplifier should
> produce 2 to 2.5
> times the plate dissapation of the tube in output. He did
> not put any
> limitations on the statement as to IMD or anything like that.
> He did not say if
> the tubes ratings would be surpassed (I am sure they would),
> but I think what
> he was saying is that the tube should continue to make power
> to 2 to 2.5 times
> it's dissapation before it would not make any more power and
> flatten out.
>
> Upon speaking with an amp "Guru" about this subject, he
> procalimed that Bill
> Orr was a "QUACK". The basis of his claim was that he was
> never able to
> build an amplifier that obtained that kind of results.
> What say you? Lou W1QJ
>
>
>
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