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

To: <>
Subject: [Amps] Tube amps are not a thing of the past
From: "Jim Thomson" <>
Date: Mon, 5 Jun 2017 07:56:48 -0700
List-post: <>
Date: Mon, 5 Jun 2017 06:36:47 -0400
From: Herbert Schoenbohm <>
Subject: Re: [Amps] Tube amps are not a thing of the past

<Tubes in High Power Amps can take a licking and keep on ticking...but 
not solid state amps devices.  Replacing power MOSFETS in RF pallets is 
much more complicated.

On 6/5/2017 3:46 AM, Roger (K8RI) wrote:
> OTOH as W8HW said, the input of the high power devices is extremely 
> fragile. Over drive and spikes of very short (few Ms) duration that 
> wouldn't faze a tube can be fatal for SS devices. 

##  a  4CX-1000 has ZERO watts of grid dissipation.  A  4CX-1500B is
not much better, at only 1 watt.   They both require fast grid over current
protection, like <  100 microseconds.   A 8877  also requires fast grid
over current protection.   ON4UN took out the grids in his hb  2 x 4CX-1500B
amp years less than the blink of an eye.   The GM3SEK  tetrode board
has grid overcurrent  

##  Nobody ever blew the grid out of a 3-500Z.   The 225 watt  CCS grid
in both the 3CX-3000A7 and also 3CX-6000A7 are indestructible.   With the
grid flange bolted to the cold chassis, the grid diss is further increased.
A buddy had his ipa  go nuts one night, and it stuffed 2 kw into the 
of the usual 500-700 watts.  Nothing happens.   A simple  3agc rear mount fast 
fuse, wired between chassis  and negative terminal of grid meter..or grid shunt 
plenty of safety.   Fuse opens up, no path for DC grid current, amp cant be 
driven, power
output drops to zero watts,  input swr rises to infinity, xcvr shuts down, 
event over. 

##  I can see where the SS amp revolution is going to surpass tube amps, and a 
lot quicker 
than  5-10 years.  More like 1 year, 2 max.  Tubes will be relegated for high 
power use, like
5-15 kw.   Even  2 or 4 of these SS amps could be driven through a 
splitter....then a combiner on the
output side..which has already been done.   Then the pre-distortion sample 
could be derived from
the output of the combiner. 

Jim   VE7RF  
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