Hi: I have an AG phono but the configuration is slightly different than yours. I bought mine directly from George Wright since I only lived 25 miles from him. Mine uses 4 12ax7s and one ecc99/12bh7. You have the correct tubes. I haven't experienced any of the ringing you have. Do the tubes check out on a tester? George Wright advised that you should put both the preamp and the power supply "...on a hard, stable surface to avoid microphonics(vibration pickup) common to all vacuum-tube electronics." This is a great phono pre so I hope you solve the problem. Rob.
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