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[Amps] Alpha 8410 using 4CX1500B - why?

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Subject: [Amps] Alpha 8410 using 4CX1500B - why?
From: "Jim Thomson" <>
Date: Thu, 30 Oct 2014 08:06:38 -0700
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Date: Thu, 30 Oct 2014 10:51:07 +1030
From: "Leigh Turner" <>
To: <>
Subject: Re: [Amps] Alpha 8410 using 4CX1500B - why?

Indeed Peter.

And high plate bias current and associated low efficiency is part and parcel
of achieving high linearity and low intermod from AB1 tetrodes.

Low plate idle current and low IMD are mutually exclusive objectives. There
are no free lunches here :-(

At least in an SSB linear amplifier one can significantly offset the impact
of high idle current with a competently implemented EBS system. When EBS is
done properly there are no audible or spectral artefacts stemming from the
tri-state transitional bias switching.


##  Unless your tri-state EBS is being used on PTT, it buys you nothing when 
using VOX.
Emtron EBS wont switch fast enough between syllables, much less words. 
No free lunch there..and ditto with ameritron, et all.  On a GG amp, you can 
run the idle current
a lot lower on ssb mode.  On CW mode, you can easily reduce the idle current to 
just above zero. 

##  2 x 4CX-1000s   vs a single 8877 ?   No brainer there folks.  The 8877  
wins hands down.
2 expensive breech block  sockets, 2 tubes, 2 chimneys, 2 parasitic 
suppressors, regulated screen supply,
zero watts grid diss, no thanks. The list goes on and on.   Then to top is all 
off, the 4CX-1000 is no longer available. 
Its yet another of alphas silly tube lineups.  

Jim  VE7RF

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