I'd agree with the question, "how does the problem manifest itself?". I use
a Paragon to drive the Centurion (which does have low pass filters for each
band on the input). I'd suppose there is enough stored energy to provide
counter EMF when the tube input Z is on positive peaks.
Perhaps I don't see it as this only relates to amps that have only a passive
input.
73
Bob, K4TAX
----- Original Message -----
From: "Michael Tope" <W4EF@dellroy.com>
To: "2" <2@vc.net>; "carl seyersdahl" <carlseye@tampabay.rr.com>; "AMPS"
<amps@contesting.com>
Sent: Saturday, May 03, 2003 6:20 PM
Subject: Re: [Amps] G-G Amplifiers With No Tuned Input.
> How does the problem manifest itself, Rich. I have used the
> Alpha 78 quite a bit with a Kenwood TS-940, Ten-Tec
> Paragon, and Kenwood TS-950SDX. All of these rigs are
> solid state, but don't seem to have any trouble driving the
> Alpha 78.
>
> BTW, the Paragon uses relay switched low-pass filters (5
> pole I believe) to filter the output of their PA. I suspect
> Kenwood does similarly. These filters may be providing
> the needed energy storage to average out the non-linear
> impedance presented by the unfiltered cathode input on the
> Alpha 78.
>
> 73 de Mike, W4EF.......................................
>
> >> Amplifiers such as the MLA-2500, SB-230, 374, 78, and 76PA have no
tuned
> >> input. This is not a problem when such a g-g amplifier is driven by a
> >> tube-output radio such as the TS-830S. The reason is that although the
> >> input Z of a cathode-driven triode fluctuates from roughly 1/3 of the
> >> average driving Z on negative peaks to a virtual open circuit on
positive
> >> peaks, the Pi-network tuned circuit in a tube-output radio acts as a
> >> flywheel to smooth out the Z fluctuation at the cathode/s.
>
>
>
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