In Reply to: Everyone said it could not be done??? posted by TomWh on November 10, 2014 at 07:18:06:
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.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: Everyone said it could not be done??? - drsx 10:27:00 11/10/14 (8)
- RE: Everyone said it could not be done??? - Paul Joppa 17:27:21 11/10/14 (7)
- RE: Everyone said it could not be done??? - TomWh 18:08:59 11/10/14 (6)
- RE: Everyone said it could not be done??? - Paul Joppa 19:11:50 11/10/14 (5)
- RE: Everyone said it could not be done??? - TomWh 07:38:02 11/11/14 (1)
- RE: Everyone said it could not be done??? - Paul Joppa 21:41:48 11/11/14 (0)
- RE: Everyone said it could not be done??? - Donald North 19:43:53 11/10/14 (2)
- RE: Everyone said it could not be done??? - TomWh 07:48:21 11/11/14 (1)
- RE: Everyone said it could not be done??? - Donald North 08:16:59 11/11/14 (0)