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RE: Everyone said it could not be done???

If your RIAA filter relies on the plate impedance of the tube for correctness, it will never be quite correct, and it will change with the age of the tube. Obviously there are lots of tube phono stages that ignore this and do just fine, so whether it is an issue worth worrying about or not is up to you.

Ways around it include using pentodes for gain (where the plate load will dominate the output impedance), using a cathode/source/emitter follower before the filter for increased consistency, including a series resistor which will dominate the impedance, etc. DHTRob's solution doesn't strike me as ideal.


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