[Amps] 572B AMP PLANS

[Hsu]

Jeff,
 In  your experience, how long tube life of GI-7B?
           Hsu 
----- Original Message ----- 
From: "Jeff Blaine" <keepwalking188 at yahoo.com>
To: "Roger (K8RI)" <sub1 at rogerhalstead.com>; <amps at contesting.com>
Sent: Monday, December 27, 2010 7:19 AM
Subject: Re: [Amps] 572B AMP PLANS


I cannot think of a single reason, that means zero reasons, to build with a 572b.  The GI7B is a far far far far far superior tube 
(did I say far superior? hi hi) than the 572b.  And all the rest of the amp is essentially the same.  1 GI7B = 2 572b from a power 
standpoint.

You can buy GI7BT at a reasonable price from QRO-STUFF.COM.  They will ship from a TX warehouse but the freight term is a bit odd. 
The way it works is you get the delivery from TX, but you pay for a partial shipment cost for the original transit from Russia - 
which is why the freight cost seems so high.

2500V is the sweet-spot for B+ on that tube as well.  A pair of them well ventilated will run about 1KW out on the lower bands and 
remain under the 700W plate dissipation limit for a pair.  Match that with the G3SEK triode control board and you will have a modern 
amp.

Having said that, one thing to consider - it's often more expensive to build unless you have a lot of time to hunt around for parts 
on the cheap or unless you have a well stocked junkbox (most guys don't).  And to an extent, the same caviet applies to doing mods 
on something like an SB200 - I beleive I must have the only $3000 SB200 upgraded amp on the planet!  So if you are thinking you can 
build for less than buying, you can get pretty far toward your goals with an AL80 which is a much superior amp to an AL572 and uses 
a much more rugged tube.

Good luck.

73, Jeff ACØC
www.ac0c.com