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[Amps] first time questions

To: amps@contesting.com
Subject: [Amps] first time questions
From: Ulf Tjerneld <star@frizon.org>
Date: Sat, 16 May 2009 17:38:44 +0200
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Hi all,

I'm collecting parts for an amp-project. And I have som newbie  
questions:

1, Maybe this question is silly: When calculating the Pi network for  
an amplifier with  GI7-B's I'm aiming for an unloaded plate voltage of  
2500 volts. With one tube this means that the plate current would be  
350 mA for an input power of about 875 watts and not dissipating more  
than 350 watts. If I'm instead going to  use a pair of tubes, this  
means that I would input 700 mA in the Pi network formula. Right?

2, I have a perfect capacitor for the Pi-tank in the above example.  
But is rated exactly 2500 volts (Johnson something...). Would that be  
to little for an unloaded plate voltage of 2500 volts?

3, Most people that builds amplifiers based on the GS35B use a plate  
voltage of around 3500 volts. This would mean a plate current of about  
700 mA for 2500 watts input. But let's say I only have 2500 volts, but  
enough iron in the transformer. Would I achieve equal results if I let  
the the tube draw more current? I.e. let the tube run with 2500 volts  
and a plate current of 1 A? And to extrapolate further, even go to a  
plate voltage of 2000 volts resulting in a current of 1.3 A? To  
summarize: does it matter what combination of voltage and current I  
use as long as it is within the specs of the tube?

All the best

Ulf/SM0NOR


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