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In Reply to: RE: Elrog 300B posted by alexz on January 30, 2015 at 23:33:18
I was confused. I thought you said Ug ~-75v, Ia ~85ma, Ua 425v
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
Tube is cathode biased with 900ohm resistor. That is in one of the posts.
If you are after precise nubers, here they are:
Anode 427v
Cathode 77v
427-77 =350v Ua
77/900=85.5555 ma Ia
Ug is -77v in relation to cathode
Is it still confusing ?
No. Not that part.
But more heat (and more light) from the filament, being produced by the same total input power at the same frequency, is confusing to me. Then again, I don't understand these things all the well. As you point out, the tube has plenty of emission.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
You can make any temperature with any wattage by choosing the wire size. Thus there are 7-watt light bulbs (drawing about 1.2A at 6.3v). They operate at the same temperature as 100-watt bulbs, just more surface area to make more light.
The issue is that the maximum emissivity of tungsten is much lower than oxide filaments. No one is saying what strategies Dr. Elrog is using, but there are several available.
Now it is my turn to get confused:
Is it tungsten filament containing thoria to get high emission ?
Or is it tungsten filament coated with Th02 for stability ?
Edits: 02/01/15
,
Have Fun and Enjoy the Music
"Still Working the Problem"
But if we use a different wire size then won't that draw a different current? We can adjust the voltage to keep the wattage the same but I though we are stuck here with 5 volts and 1.2 amps? (and, I would assume to some extent, surface area)
Anyway, if it works, it works.
I wonder why the lower audio output power?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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