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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

help with my humming valve amp

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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.😕
 
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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