[AMPS] 4-1000A amp design

[Bob Sutton]

At 16:49 10/08/98 -0500, you wrote:
>
>> I found the 50 ohm tapping point was about 1 turn down from the tube.
>>This circuit worked like the article said it would, and several other
>>amplifiers have been altered to use this form of input tuned circuit.
>>Results ... 5.2kV HT on the anodes, 120W drive from TS-830, 3000W RF into a
>>dummy load  ;-)  with hardly a glow in the plates ... it runs as cool as a
>>cucumber. 
>
>Is this grid driven or cathode driven?  Impressive!
>

Cathode driven.  I tried it as a grid driven pair of 4-1000's but gave up
in frustration ... all those power supplies and mediocre results!  I know
others who have succeeded with grid driven, but the cathode driven
arrangement is MUCH easier.  

I was impressed too after the results I had building a single tube amp a
few years previously using a conventional bifilar wound filament choke on a
ferrite rod and "L" matching network at the input.  Overall the single tube
amp with the choke cathode input circuit didn't quite have the 'apparent
anode efficiency' as the two tuber with the "coaxial coil" tuned circuit
input circuit, but it was very adequate.  From memory, that one tuber
delivered 1900W output with 4500V HT and about 120W of drive.  

I might add that I didn't have any trouble with stability/oscillation in
the single tube amp using a plastic 4-1000A tube socket.


73 ... Bob, ZL1RS

Visit my web site which includes photos from my recent 
ZL8RS Kermadec operation ... http://www.qsl.net/zl1rs/



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