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Re: [Amps] Alpha 8410 using 4CX1500B - why?

Subject: Re: [Amps] Alpha 8410 using 4CX1500B - why?
From: Vic Rosenthal 4X6GP/K2VCO <>
Date: Wed, 29 Oct 2014 09:16:11 +0200
List-post: <">>
I believe the difference between the 1w grid dissipation rating of the 1500 and the 0w of the 1000 isn't significant and may only be a matter of how the engineers decided to present it on the data sheet.

The 1500 has a different grid structure that is designed to produce lower IMD than the 1000 (which is no slouch in that respect itself).

When operated according to specs the 1500 does produce less output than the 1000 because it is less efficient. Hence the utility of additional plate dissipation.

Incidentally, the Chinese 4CX100As sold by Alpha have the same kind of anode cooler as the 1500s -- there is more fin area -- and so may have more reserve plate dissipation.

On 28 Oct 2014 23:32, Prem wrote:
The first thing that comes to my mind is, the grid dissipation is 0W
(4CX1000A), and the plate dissipation is lower than a 4CX1500B.

I'm not sure about the o/p being lower in the 4CX1500B; should be higher as
per specs.


On Tue, Oct 28, 2014 at 4:35 PM, Peter Sils via Amps <>

I recently acquired a slightly used 8410 (mfg 3/2014). I was surprised to
learn it had 4CX1500B tubes rather than the 4CX1000A's.

Looking at the RF Concepts website for tubes I notice the price is lower
on the 4CX1000A ($475) than the 4CX1500B ($525).

 From what I have gathered the drive requirement is higher and the output
is lower.

Can anyone shed light on why Alpha chose to go with the 4CX1500B's?

TNX in advance of your insights!

73 Peter

Vic, 4X6GP/K2VCO
Rehovot, Israel
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