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the 811A tubes seem to be good for about 200 watts each and look to be around for a while . does anyone make a amp using just 1 or 2 of them ? its the first few hundred watts that make the biggest difference ......
thanks

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I think if you were going to find an amplifier using 811's you might as well start looking to for a three-tuber. I'm not aware of any two tube 811 amplifiers, and a single 811 amplifier just isn't worth the time and effort normally.
You want to be very careful about that 200 watts per 811, that's just not what you'll get. That's what it seems to be when you see a multi-tube 811 amplifier, but just remember that 200 watts is in SSB mode, and is actually 'pushing' those tubes about as hard as they can be pushed. You will never see that when in AM mode. At least, not for very long LOL.
A single 811 might be capable of 30 - 40 watts in AM mode, and that would be pushing it.
- 'Doc


In the long run, under driving a slightly larger amplifier to a very low power output is a much better idea. Larger cost to start with, but it sure ought to last forever.

Yeah it's all about the duty cycle.

That and a lot of the parts to build an amp cleanly add up quickly so a clean lower power amp doesn't come cheap.

After juggling it around for months, wanting 500W full duty cycle for SSB, I got a single 3-500ZG AL-80B used for $750. Bang for the buck was really high and it has plenty of headroom to just set and forget at 500W for all the rag chewing I can do.

AM guys seem to have long life keeping them down around 100W carrier too. It's only when you push them past their duty cycle that you have trouble.

It will run a few hundred higher on SSB no problem too coming up to about a kW depending on the band. I heat it up about once a week to keep the gas out of the tube, but generally run it with low drive 50W or so to take it easy on my rig and the tube.

I have some schematics around for single/dual 811A amps, they are old and intended strictly for 10/11 meters, there are also quite a few on the net, both multi, and single band.

Maybe its time to up the ante on your hobby, and build one, its not terribly difficult, only thing is safely handling the High Voltage. If you scrounge parts you should be able to do it relatively inexpensively, Even the plate transformer for such an animal could be had cheap, or possibly even free.


I can't entirely disagree with the other comments, but I do know your goal is probably not sinking 700+ dollars into this.

Another option is to watch Ebay, old 811 builds pop up relatively often, sometimes dirt cheap, would be a great source for parts.. Might get lucky and score an old amp in working condition as well.

I would just find a Heathkit SB 200 and run it easy. 8 watts dk 50 pep. should do 100 watts avg 400 pep.