Transmitting Triode Amps

[dhaen]

Wow!

The beauty ot this one seems to be that it doesn't need forced air cooling (at reasonable powers).
This thing can take as much grid current (75mA) than the usuals can take though their anode (plate).
I wonder what the Ra (Rp) is. I notice that the linked company makes OPT's with 30k primaries, so perhaps it's about 10k.
If this is the case, it might be difficult to equal the performance (other than power) of the commoner 211, 845, 572 etc, without very special attention to transformer design.

Thanks for the link!

[Brett]

Look at Lancroft tramsformers site. They have trannies, and at least 2 designs for the beast there. Supplies are up in the 1500V+ range which makes it a heck of an expensive amp on parts.

http://www.users.bigpond.com/triode/833A1.html

Then there's always the GM70, which AudioXpress has an article on about a year ago, and iirc, it was 30W. They are $US50 new from KW Tubes (he's on holidays till end of July).

http://kwtubes.s5.com/

Or the GM100. Now this is a man size tube. Almost literally.

http://www.vt52.com/diy/myprojects/amps/gm100/gm100.htm

Makes the 833A look like a pokemon

[dhaen]

Let the boasting about size end here!


Yes I know and love the GM70. I'm currently building an SE amp that will run with 845's or GM70's.
The trouble with these biggun's is the heater power. Makes hum reduction a "non trivial" problem in SE. Still, it's lucky my speakers are not too efficient.

[steve jones]

What are the heater requirements on the GM-70? I might have a cheap slick option to try.

[dhaen]

They are 20v 3.25A as far as I remember..

[steve jones]

Take a look at this:

http://www.expresslighting.com/eltran24.html

An 11.6V/5A@>20khz version was posted on the TubeDIY Asylum, by Par.

I haven't tried 'em yet (probably have to choke filter the output switching noise), but hum should be non-existant with ultrasonic AC heating. And you could throttle/trim the output voltage with a dimmer.

[Brett]

Originally posted by dhaen
Let the boasting about size end here!

My transmitter tubes are not compensating for anything. <i>Really</i> they're not. I'm going to build a 6S45 spud amp just to prove it.

The trouble with these biggun's is the heater power. Makes hum reduction a "non trivial" problem in SE. Still, it's lucky my speakers are not too efficient.

I'm going to use either DC current source heaters in the 813PP (10V, 5A each) or high frequency regenerated linear supplies. The lighting controller is a nice turn-key idea, but I wonder how much RF garbage will end up in the amp (DHTs remember) or put out into the mains. Think of what the average household LV dimmer can do, and these are designed for a much less sensitive environment. However Par is usually pretty good, so....
HF AC heaters were also discussed on Tube -DIY a bit recently.

Cheers

[martioz]

I would like to add my cent to this discussion a bit out of topic .
Q:
Does anybody order something from vv52.com?
Just seeking more info about liability of the seller.
Thanks,

[martioz]

Oops wrong URL,
Correct one:
http://www.vt52.com
Cheers,

[dhaen]

I ordered some valves (tubes) from Jim de Korts other company http://www.triodes.nl/.
After 2 months and many emails (mostly mine), they eventually turned up.
I do not know who's fault the delay was, but it was not delayed in the UK because the package had a Dutch postmark of 2 days previous.
Those are the facts.