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Old 23rd January 2012, 05:30 PM   #1
wicked1 is offline wicked1  United States
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Default Pentode Regulation Question

I'm building a 6v6 pp amp in pentode mode. I want to regulate the screens.
The screens run only 5v lower than the anode. I'm afraid that if I only regulate the screens, the anode could drop below the screen voltage w/ power fluctuations. That's a problem, right?
And then if I regulate b+ and drop the screen voltage from there, would the screens still be regulated, since b+ is? What about using a diode to drop the screen voltage from the regulated b+?

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Old 23rd January 2012, 05:35 PM   #2
TheGimp is offline TheGimp  United States
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If you regulate the screen supply, the anode will go below the screen during less than half the cycle.

Yes, you can develop the screen supply from the anode supply, however unless you use a very good regulator for the B+, some ripple and signal modulated noise will couple to the screen.

You can a run the screens at a lower voltage, but it will suppress Gm to some degree depending on how low the screen supply is.

Post a complete schematic with voltages please.
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Old 23rd January 2012, 06:15 PM   #3
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You can regulate all as you want, but have in mind that for several decades, the 6V6 had been working in AA5 radios, amplifiers and TV sets without any regulations. It is not necessary at all.
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Old 23rd January 2012, 06:22 PM   #4
wicked1 is offline wicked1  United States
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Well, I'm basically designing it now. 12at7 ltp w/ ccs to the 6v6's. B+ will be 360 and screens 355. At least, that's how the original amp was set up (ampex 620's) (The full story is I've got a pair of old ampex 620's and am re-building them.. Re-using the chassis and iron are the only real design goals). Regulation will likely be a Maida regulator.
I'm sort of envisioning a pentode "el cheapo" type amp.
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Old 23rd January 2012, 06:25 PM   #5
wicked1 is offline wicked1  United States
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Quote:
Originally Posted by Osvaldo de Banfield View Post
You can regulate all as you want, but have in mind that for several decades, the 6V6 had been working in AA5 radios, amplifiers and TV sets without any regulations. It is not necessary at all.
I know... It's basically all for experimenting/learning/fun. It will definitely be unnecessarily complex.
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