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Re: Latest version of my 7788/7721 LCR 600Ohm RIAA Stage

How to measure? Easy. Disconnect any input transformer or cartridge. Measure the voltage across the 47K input resistor, divide by 47K and that's your input grid current. Also, measure plate current if possible (or plate voltage) and then alternately short and then leave alone that 47K resistor. If there is any significant change in plate current or voltage, then you have to suspect grid current.

If you are using a transformer, then there should be no problem, but those who connect your RIAA stage directly to a cartridge, whether MC or MM, should consider either a different design with more grid bias or an input transformer,IMO.


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