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Re: [Amps] Plate coupling capacitor value

Subject: Re: [Amps] Plate coupling capacitor value
From: Chris Wilson <>
Reply-to: Chris Wilson <>
Date: Fri, 8 Sep 2017 08:50:09 +0100
List-post: <>

Hello John,

What  value  blocking  cap  would  you  suggest  for a 136kHz amp I am
building using a single GS35B tube? Thanks.

On Friday, September 8, 2017,  you wrote:

> The capacitive reactance Xc of the plate DC blocking ppcapacitor should
> be chosen so that on the lowest frequency it has a low value of ohms. 
> This way it doesn't have a significant RF voltage across it, which 
> results in heating and loss. On the other hand, if the capacitance is 
> much larger in value than required for the lowest frequency, usually 
> some self resonance in the capacitor will begin to act up on the higher
> frequencies. Also, a larger than needed capacitor may cost more. A 
> single capacitor usually suffices in the application for amateur 
> service. If two paralleled capacitors are chosen, they should be mounted
> on flat straps equidistance to the pi-net and to the plate. This will 
> produce equal inductance for each cap, so that they share current well.

> 73
> John

Best regards,

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