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Old 11th January 2010, 06:48 PM   #1
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Default help with my humming valve amp

Hi everyone.have a problem with my valve preamp.the problem is that i am getting a loud humming from my horn speakers,and it has been getting louder over the last few months.i know it is a problem with the amp because i had a solid state amp that did not cause the humming.also when i put my hand on one of the external capacitors the humming dies down alot,i was thinking it was an earth problem ,can anyone help me pleeeeeease.
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Old 11th January 2010, 07:50 PM   #2
SY is offline SY  United States
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Could be a lot of things. What sort of preamp is it? Do you have any experience with working on tube gear? Test equipment?
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 12th January 2010, 07:26 PM   #3
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Hi sy,the preamp is a ming da mc7r
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Old 13th January 2010, 07:39 PM   #4
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have just come in from long day out with family and sat down with a glass of red wine to listen to music ,as i put the preamp on i put my hand over the 2 left vales 12ax7, 12ua7 .as i did this the humming died down ,and here was me thinking it was the capacitors,that was because i had my hand over the valves while touching the capacitor. so now i am thinking it is not the capacitor but an earth problem.
the tubes are sylvania (baldwin) maching pairs .the strange thing is my old japanese tubes did not die down when i had my hand over them but the sylvania do ??? very puzzled indeed. i took the earth off the monoblocks but it made no difference so i put it back on. would love to hear any ideas .thanks.
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