Just a quick question.
Has anyone had this! I have found that signal tubes ECC 81 etc when used with DC heaters start making a sound when amplified through the speakers! Sounds like someone dragging their nails across the back of the speaker cone. If you tap the tube it has become "mechanicaly noisy". If you change to AC heater supply it does not happen!
Regards
M. Gregg
Has anyone had this! I have found that signal tubes ECC 81 etc when used with DC heaters start making a sound when amplified through the speakers! Sounds like someone dragging their nails across the back of the speaker cone. If you tap the tube it has become "mechanicaly noisy". If you change to AC heater supply it does not happen!
Regards
M. Gregg