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mechanical hum
mechanical hum
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Old 26th May 2007, 02:49 PM   #1
Bill*B is offline Bill*B  United States
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Default mechanical hum

Just picked up a pair of tube monoblock amplifiers - Quicksilver KT88s - one is dead quiet, the other has a rather loud mechanical hum. The output signal - through the speakers - is fine. This is a hum at the amp itself, so I assume it's power transfomer related. I can't feel any vibration - the mounting screws are tight - any ideas? Regards, Bill.
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Old 26th May 2007, 03:01 PM   #2
beamnet is offline beamnet  Netherlands
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Failing power relais (if it has one) or bad transformer. If the latter there are ways to reimpregnate them using diy stuff

Sometimes bad rectifier tubes can cause noise too..
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Old 27th May 2007, 12:02 AM   #3
Jeb-D. is offline Jeb-D.  United States
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One of my amps does that. I think because do to the nature of the design I had to half wave rectify it which causes an asymetrical flux swing. This is probably not the case for you though, but I know how annoying it is. I've considered filling the transformer end bells with epoxy to dampen it. Or making a dummy load to load the negative half cycle, but this option is a waste of energy and my inner tree hugger won't let me do it.
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Old 30th May 2007, 05:38 PM   #4
Bill*B is offline Bill*B  United States
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Thanks! Bill.
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Old 30th May 2007, 10:42 PM   #5
greenvalve is offline greenvalve  United States
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My first comment ay DIY audio... I thought maybe I could help you out, since I had a mechanical hum on my PS Xformers as well. What finaly cleaned it up was to install a ' DC blocker circuit ' on the 120V primaries.

Looks like this... (thanks Yeo @ diyparadise.com)
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File Type: gif transformer dc blocker schematic.gif (2.8 KB, 114 views)
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