I looked in all my industrial strength tube data sheet binders (GE, Wstgh. etc.) plus some old reference's and it's not mentioned anywhere. But we do know the amplification factor or mu (µ) is 160.
Gm = µ/Rp Therefor, if you figure the plate resistance for the circuit parameters used, you can compute the Gm.
To use round numbers, an Rp of 10K ohms would give a Gm 16,000 micromhos.
Gm = µ/Rp Therefor, if you figure the plate resistance for the circuit parameters used, you can compute the Gm.
To use round numbers, an Rp of 10K ohms would give a Gm 16,000 micromhos.
nhuwar said:I was thinking about using it as a pass tube in a regulator...
OMG, why would you want to use (waste?) such a nice tube in that service? Oh well, I just happen to like this tube and it's relatives the 812A, 809, 1623 & 8005.
OMG, why would you want to use (waste?) such a nice tube in that service? Oh well, I just happen to like this tube and it's relatives the 812A, 809, 1623 & 8005.
The Chinese 811a's are cheap and plentiful and handle 65 watt Pd intermittently. I would rather use them than a 6550 or 6L6.
Hollow state astouffer has it right I can get a matched quartet of Chinese 811a or jans for cheap.
Funny you mentioned the 812a, that bad boys on my too do list of amps to build. But as for the application there isn't many other tubes that are affordable that will handle the current.
Originally I was plaining on using as 4-400 as the pass tube but I would be too close to the max dissipation to not forced air cooling, plus the filament transformer. The transconductance on the 4-400a isn't that high either.
Trust me I don't hold the 811a in low regard, it's just it fit's the application too well to pass it up.
Nick
Funny you mentioned the 812a, that bad boys on my too do list of amps to build. But as for the application there isn't many other tubes that are affordable that will handle the current.
Originally I was plaining on using as 4-400 as the pass tube but I would be too close to the max dissipation to not forced air cooling, plus the filament transformer. The transconductance on the 4-400a isn't that high either.
Trust me I don't hold the 811a in low regard, it's just it fit's the application too well to pass it up.
Nick
nhuwar said:So Hollowstate have you used the 812a in a amp?
No Nick, I have not...not yet anyway. I have a good collection of 812s and a new pair of Electra Print 10K PP transformers that I got off eBay a couple of years ago. They are big and probably in the 50 to 60 watt range. In fact I have everything I need except time. Unfortunately earning a living gets in the way.
HollowState said:
No Nick, I have not...not yet anyway. I have a good collection of 812s and a new pair of Electra Print 10K PP transformers that I got off eBay a couple of years ago. They are big and probably in the 50 to 60 watt range. In fact I have everything I need except time. Unfortunately earning a living gets in the way.
Tell me about it. I know what you mean.
Nick
Bandersnatch said:hey-Hey!!!,
811A will need high plate voltage or grid current to pass reasonable amounts of current. Tubes designed for pass element serivce have minimum plate resistance( and usually mu ). The error amp takes care of the low mu factor.
cheers,
Douglas
Knowing Nick I am sure very high plate voltages are not really a problem..
kevinkr said:
Knowing Nick I am sure very high plate voltages are not really a problem..
At least he won't have to worry about heater-cathode ratings...
cheers,
Douglas
nhuwar said:Heater current, ah that thing doesn't pull hardly anything. If a tube doesn't pull more then 40 amps on the heater I conceder it a low current heater LOL.
Nothing to worry about
Nick
ooops...heater-to-cathode... it's the same thing; no need to worry about isolating/insulation between the two.
cheers,
Douglas
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