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Re: [Amps] Tube amps are not a thing of the past

Subject: Re: [Amps] Tube amps are not a thing of the past
Date: Mon, 05 Jun 2017 13:00:16 -0500
List-post: <>
I have never liked the 30S-1 grid derived ALC.
The grid voltage is passed through ( essentially ) an audio transformer and
the tube has to draw grid current before the transformer's secondary is rectified for an ALC voltage.

Sure, it's RF Frequency independent, but a cathode voltage sample with an adjustable ALC control would be better to prevent grid current BEFORE it happened.


Quoting Gary Schafer <>:

Hi Jim,
I think that the 4CX1500 has the same grid as the 4CX1000.
Somewhere I have seen it written by Eimac that it is ok to draw a small
amount of grid current during brief tune up.

The Collins 30S-1 (4CX1000) develops ALC from grid current.

Gary  K4FMX

-----Original Message-----
From: Amps [] On Behalf Of MU 4CX250B
Sent: Monday, June 05, 2017 11:03 AM
To: Jim Thomson
Subject: Re: [Amps] Tube amps are not a thing of the past

I've long wondered what the zero watt rating of the 4cx1000 grid
actually means. I've assumed it means the tube is rated for class AB1
operation only, and that the rating doesn't reflect the actual
physical limitation of the grid structure.  I wonder if anybody has
actually cut apart a tube and inspected the grid?
Jim w8zr
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