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[Amps] How high can I go with this amp?

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Subject: [Amps] How high can I go with this amp?
From: "Steve Flood" <>
Reply-to: Steve Flood <>
Date: Sat, 10 Oct 2009 05:52:23 -0600
List-post: <">>
Can I get more output power/efficiency with a smaller inductance coil in my 

Power supply is 2700v key-down and capable of 800mA (it is built around an 
SB-220 transformer).
Ip meter max is 750mA.
Amp is 3 x 813.

Pi-net designed around RL of 2333 ohms.  Pi tank is variable caps and fixed 
coil. Design Q is 12.
Currently, my input power is 2700v x 600mA = 1620w.
Output measured on scope is 1111w.
Efficiency is 68-69%.
Plate dissipation is 176w per tube.
These figures are based on CW with adjustable bias set for 0mA ZSAC.
Grid current is 150mA (50mA per tube).
Drive is 100w through input pi net.

What if...?
I decrease the coil inductance to lower the RL to 1800 ohms.
It seems this will allow me to generate higher Ip and input power - say 2700v 
at 750mA = 2025w.
If I  can maintain 68% efficiency, I could theoretically get around 1370w out.
Or does the tank modification allow me to go well into class C - say 75% 
efficiency or close to 1500w out?
Or will my drive power limit how high I can go?
I'm just talking about CW here.

What am I overlooking?  I am trying to figure out what the amp is capable of.  
I know the extra power makes little difference on the other end, and I'll have 
extra heat and tube stress.

Steve, KK7UV

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