[AMPS] Cathode input networks resonant or not?

[Richard W. Ehrhorn]

-----Original Message-----
From:	Rich Measures [SMTP:measures@vc.net]
Sent:	Saturday, August 29, 1998 5:32 AM
To:	'amps@contesting.com'
Subject:	Re: [AMPS] Cathode input networks resonant or not?



>>I submit - admittedly without PhD-level academic documentation but based 
on
>>hands-on experience - that if the cathode network isn't resonant AT OR 
FAIRLY NEAR the operating frequency there's no "flywheel."

>>......
>the hands-on measured frequency of resonance of a pi-network (2
>pi-networks in series) is near the operating frequency, however, the two
>frequencies are not the same.

>Rich...

>R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures


Presumably you "hands-on" MEASURED the resonant frequency with the amp 
turned OFF, or at least with tubes biased to cutoff. In either case the 
tubes look basically like a capacitance across the output of the input 
pi-net.

Presumably also, you'd ADJUSTED the pi-net WITH DRIVE so that the tubes 
looked more or less like a capacitance (which probably varies a bit over 
the cycle) in parallel with a highly nonlinear resistance.

That (nonlinear) resistance is across only part of the total pi-net 
capacitance which determines resonance. I think a simple experiment will 
show that the "dip" frequency of a pi is somewhat dependent upon the 
terminating load R. That's what I seem to recall theory predicts. Maybe 
it's no mystery!

73,  Dick



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