Philips never made a GZ37. What you have is a rebranded Mullard.
For the record, my 6106 never matured to something I appreciated. I have recommitted to my double D getter metal base GZ34.
6SN7s really aren't anymore prone to microphony then other tubes. It's really the fault of the Supratek implementation. I have never heard a line stage so sensitive to tube noise then the Supratek. When shopping for Supratek 6SN7s, request "phono grade" tubes if your dealer can test for microphony.
For the record, my 6106 never matured to something I appreciated. I have recommitted to my double D getter metal base GZ34.
6SN7s really aren't anymore prone to microphony then other tubes. It's really the fault of the Supratek implementation. I have never heard a line stage so sensitive to tube noise then the Supratek. When shopping for Supratek 6SN7s, request "phono grade" tubes if your dealer can test for microphony.