AL811 and 572Bs

[N8XE]

Hey guys,

I have a vintage amp that has 4 original (early 70s) Centron 572Bs in it. The amp is fairly large and occupies a lot of space. Plus, it lacks a tuned input which makes it a joy to tune with my solid state rigs.

So I was thinking of selling off some QRP gear (oh the irony!) that is collecting dust and get an AL811. I would take three of the 572Bs out of the current amp and place them in the AL811. Is this something that is doable? It would be about the same power output (the old amp is set up for 600 watts). The AL811 would occupy less desk space too.

From what I gather, the 572Bs can go into the 811 without any mods.

Thoughts?

Jason N8XE

[WX7G]

This will work well.

[AF6LJ]

Why not.....
simply modify the existing amplifier with a tuned input?
You have a nice box there, get some use out of it.
If you cannot modify it you can find someone credible who can do it for you for a reasonable price.

[WB2WIK]

Jason, what's the vintage amp?

GSB-200 or -201? HA-10? What is it?

[N8XE]

Jason, what's the vintage amp?

GSB-200 or -201? HA-10? What is it?

It is homebrewed. Nice one too. It was made in the late 60s early 70s.

It is built in a Hallicrafters receiver case so it is big and heavy (the power supply is built for the voltage needed... it does not have any voltage doubling circuits in it)

Jason

[N8XE]

Why not.....
simply modify the existing amplifier with a tuned input?
You have a nice box there, get some use out of it.
If you cannot modify it you can find someone credible who can do it for you for a reasonable price.

Sue,

That is another alternative. The problem is that I would need to put another switch in there (or get a switch that can not only switch the output network but also the input network too). And I need to see if there is room for the input network to work.

Ideally this is what I would like to do. But the amp is pretty darned big.

Jason

[WB2WIK]

Sue,

That is another alternative. The problem is that I would need to put another switch in there (or get a switch that can not only switch the output network but also the input network too). And I need to see if there is room for the input network to work.

Ideally this is what I would like to do. But the amp is pretty darned big.

Jason

It may be tricky to index a switchable input network the same as the existing bandswitch unless you happen to have an extra double pole wafer that's indexed the same way as the plate bandswitch is; however, a "second" bandswitch just for the input circuits is pretty easy, or of course if you're handy mechanically you can do strange stuff like Henry did in most of their amps, where in the input network switch was activated by a chain drive, using a sprocket on the main bandswitch shaft. That seems nutty but it worked fine, and I've never seen one break.

[W0JBC]

Steve , you have answered many questions concerning this topic .

Good for you .

JB

[K3STX]

Jason,

I love my AL-811. 450 watts out on CW with 30 watts drive, no problems at all.

See ya in SS.

paul