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RE: Wow, PPP KT-120's

600V B+ with cathode bias (~65V bias) and 70 to 80mA plate current. At present total current set to 290mA. I came up with a zero tempco CCS for the output stage "tail" CCS using a Fairchild KA431 (low tempco TL431) to control a big ass power MOSFET. I can set the bias with the amps cold and 3 hours later it's within +-0.25mA.

They're driven by a Lundahl LL1660 IT 2.5/1 with each pair of KT120s driven by its own secondary. A 6BX7GT 300V p/k @19mA/side drives the IT. It's direct connected to the 6SN7 input stage. The input and driver stages have their own CCS fed shunt regulated supplies.

Output is ~37W.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln


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  • RE: Wow, PPP KT-120's - JKT 05/7/1619:58:59 05/7/16 (0)

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