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Old 19th January 2003, 08:34 PM   #1
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Default Setting Pentode Screen Grid Voltage

I am designing a push-pull tube amp and trying to decide whether to set the screen grids at 300v. or at the plate voltage of 550. KT-90's for tubes so the screens would be 100 volts below the 650 volt max.
What are the tradeoffs as far as power, distortion, Rp, drive voltage, etc?
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Old 19th January 2003, 11:22 PM   #2
7N7 is offline 7N7  United Kingdom
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Default Re: Setting Pentode Screen Grid Voltage

Quote:
Originally posted by dshortt9
I am designing a push-pull tube amp and trying to decide whether to set the screen grids at 300v. or at the plate voltage of 550. KT-90's for tubes so the screens would be 100 volts below the 650 volt max.
What are the tradeoffs as far as power, distortion, Rp, drive voltage, etc?
No experience with beam tetrode output stages, but remember the current that these valves pass is completely dictated by the screen grid voltage - hence the flat curves: varying the anode voltage makes no difference.

If I were you I would try to obtain curves for various g2 voltages and select your operaitng points accordingly.

Your valves wil pass a lot more current with 550V on g2 - and you must also be careful not to exceed the maximum screen grid dissipation (Pg2)

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