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SSassen 11th April 2006 01:47 PM

Changing 6DJ8 SRPP stage gain
Just a quick question really. I have a textbook SRPP line stage with a 6DJ8 (ECC88) following the passive I/V and filter on a DAC which is set to amplify ~16x. The V+ voltage on the top triode is 180-volts and both cathode resistors are 100-ohm. The impedance of the load it is supposed to drive is ~10K-ohm.

I've made a few modifications to the passive filter yielding lower voltage output which means I'll have to raise the gain to meet my 2Vrms output requirement. Currently the gain is ~16.5x (24dB) but I'll need to raise it to ~25x (28dB) and the simplest way I can think of is to raise the value of the kathode resistor on the upper SRPP triode. If I raise it to 470-ohms (from 100-ohm) I meet the gain requirement.

Now here's the question; will this offset the balance between the two triodes much as they're running in a push-pull configuration?

Any suggestions are most welcome!

Best regards,

Sander Sassen

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