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

To: <>
Subject: Re: [Amps] Alpha 8410 using 4CX1500B - why?
From: "Leigh Turner" <>
Date: Fri, 31 Oct 2014 20:14:47 +1030
List-post: <">>
Yes Jim, the maximum impact bang of course comes from PTT operation...


-----Original Message-----
From: Amps [] On Behalf Of Jim Thomson
Sent: Friday, 31 October 2014 1:37 AM
Subject: [Amps] Alpha 8410 using 4CX1500B - why?

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 won't 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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