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[Amps] pandoras parasites

To: <amps@contesting.com>
Subject: [Amps] pandoras parasites
From: 2@vc.net (Rich)
Date: Thu, 7 Nov 2002 08:00:19 -0800
>I built around a single gs-35b and so far all I see is a very stable tube.It
>takes a bit more drive than a 8877 on hf but seems to be very durable.
>I did take the time to condition the tube and have not yet had any
>flash-over during operation. I`m in the process now of adding a second tube
>to this deck.
>I use anti-parasitic devices in all my amps,In my 4-1000`s (2 tubes)
>supression in the cathode side works better 

**   Since the cathode is the destination of the feedback-C in g-g 
configuration, adding a vhf-damper to gnd from each filament pin makes 
sense since the cathode is where regen must begin.  For a 3cx1200A7 (C-fb 
= 0.8pf),  a 10-ohm MF resistor in series with 33pF to gnd serves to 
absorb vhf energy that is passed back (from the damped wave ringing in 
the vhf-resonant anode circuit) by C-feedback.  Ideally the Xc in the C 
cancels the XL in the tube's internal leads at c. 90MHz.  However, this 
is obviously guess-work since one can not enter the envelope to measure 
XL.  I guess one could call this an educated guess.

>...

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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