Bond,
I lucked out somewhat. I open up the pre-amp. It uses 6 12AX7 dual triodes, 3 in the line section and 3 in the phono section. The problem was in the line section since I heard it on all inputs. So I switched tube pairs 1 by one between line and phono section. After the 3rd swap (of three total), the low level high pitched noise that sounded like a dentist drill was gone. And the phono section now with the tube that was causing the problem sounds fine! Go figure. Apparently the tube had an issue in the line stage but is quiet in the phono. I can live with that. I will be sure to pick up a few spare tubes and keep them around however for whenever the next issue comes up. Darn valves, pain in the butts but sure sound nice!
I lucked out somewhat. I open up the pre-amp. It uses 6 12AX7 dual triodes, 3 in the line section and 3 in the phono section. The problem was in the line section since I heard it on all inputs. So I switched tube pairs 1 by one between line and phono section. After the 3rd swap (of three total), the low level high pitched noise that sounded like a dentist drill was gone. And the phono section now with the tube that was causing the problem sounds fine! Go figure. Apparently the tube had an issue in the line stage but is quiet in the phono. I can live with that. I will be sure to pick up a few spare tubes and keep them around however for whenever the next issue comes up. Darn valves, pain in the butts but sure sound nice!