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Re: [Amps] power limiting in 8410 amps?

Subject: Re: [Amps] power limiting in 8410 amps?
From: GWP <>
Date: Wed, 7 Nov 2018 09:21:26 -0700
List-post: <>
Production 8410 amps have the screen voltage set to 225v.  Some very early
production amps were set to 200.
The tube operating bias is then adjusted for 200ma idle Ip and an 8410 can
easily get 1500+ watts output.

As previously noted, if the cathode resistors have changed value and are
greater than 6 ohms that will increase negative feedback, limiting the gain
and maximum output.  Just cranking up the screen voltage is not the right
way to set up an amp.

Glenn AE0Q

On Wed, Nov 7, 2018 at 6:09 AM Leigh Turner <>

> Yes I concur with this suggestion Steve.
> With only 200 Volts on the screen in AB1 linear mode the 4CX1500B tubes are
> likely being starved and held back like variously reported amongst 8410 amp
> users. The screen voltage probably ought to be up around 275 to 300 Volts
> to
> ensure unconstrained power output to 1500W+ without significant gain
> compression.
> Leigh
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