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Old 16th Jul 2006, 7:53 pm   #2
YC-156
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Join Date: May 2005
Location: Aarhus, Denmark
Posts: 281
Default Re: should this work?

Quote:
Originally Posted by adibrook
The valve is an EF80 type vari mu rf pentode...
Actually, it isn't, but that doesn't change anything here.

Quote:
Originally Posted by adibrook
So..am i doing somethign wrong here?
  • Screen dropper should be 22K for Va = 250V.
  • Ra should be 10K, not 680K.
  • Add 330 ohm cathode resistor in parallel with a 10-100nF capacitor.
This should give you a totally insane voltage gain of about 50 if the EF80 is up to scratch.

Remember that the output impedance equals the anode resistor, so this amp will not drive much of a load, especially not a capacitive one.

Frank N.
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