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What's making my system hum?

I have a  Swagman Labs linear power supply feeding the Rega TT-PSU turntable controller. Lately I have noticed a hum audible through the speakers when turned up to about 50 percent of full volume. When I switch the Rega TT-PSU back to its wall-wart power supply, the hum disappears. When I move the power supply away from the TT-PSU, the hum also disappears.

The rest of my system consists of a Rogue Audio Ares phono stage, a VTL IT-85 integrated amp, Vandersteen Treo CT speakers, and various boxes (computer, DAC, linear power supply) to play digital music. There's  virtually no hum when the VTL is set to any source except the turntable.

The obvious solution is to keep the power supply and turntable controller farther apart, but I can't help wondering what's causing this. Anyone have any ideas?
john_g

Showing 2 responses by cleeds

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cleeds
5,682 posts
 
georgehifi3,521 posts03-02-2018 1:04am
Ozzy is sort of there with lifting the grounds.
Look at your systems earthing as a whole, there should only be one earth point to the mains, as earths are carried between all the components via the interconnects.
Ground loops aren’t caused by multiple paths to ground, they’re caused by different potential between those grounds. The proper solution is to get all grounds at the same potential - eliminating safety grounds isn’t a wise shortcut. An interconnect isn’t intended to serve as safety ground, and that’s why components typically have their own safety ground.
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cleeds
5,682 posts
 
ozzy
My point was to try to find out if the ground is causing the hum. If so then work on corrections.
Yup, that's a very good way to diagnose ground loops.
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