😡hi everyone,i feel like banging my head off the wall with my vale preamp .I am getting loud humming from it ,it is a ming da mc7r ,and i have 2 mf monoblocks running to the custom built horn speakers i have. i have had this noise now for at least 6 months and cannot fix the problem.also it seems to be getting louder by the month.what i did do to it was changed the japanese tubes with some sylvania baldwin tubes ,it does sound alot nicer more open but ,,as i put my hand over the tubes the humming dies right down 😕.not a clue ?? any ideas please .thank you.🙂
A bit more information and a schematic would be helpful. Does it hum out of both or just one channel? Did you change anything to start the the unit to hum. New tubes some kind of upgrade. If it both channels hum an off the cuff guess would be a power supply problem. A bad power supply cap can cause this type problem. But whatever the problem it has to be common to both channels. If you have no or very little experiance working on tube electronics I would not recommend starting into this because there are lethal voltages involved and someone poking around high voltages who doesn't know what they are doing is a accident looking for someplace happen.
Maybe some help here
http://www.diyaudio.com/forums/tubes-valves/101360-mingda-mc-7r-noise-gain.html
http://www.diyaudio.com/forums/tubes-valves/101360-mingda-mc-7r-noise-gain.html
no i do not have any on it ,really bugging me now ,sorry not got back sooner ,but have been back home in italy for ages.
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