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Phono interconnects acting as antenna, adding noise to system

Have interesting problem with cable related noise. I have a coincident phono amplifier and biamped coincident speakers with dedicated 20 A circuits from a separate panel share a common star ground (independent from rest of house).  

There is not ground hum, but when phono to amplifier interconnects connected to amplifiers a course EMF like noise occurs.  The cables seem to be acting as antennas since the noise does not change if disconnected from phono amp but stops if disconnected from power amplifier.

Interestingly, the interconnects are 12feet long running in galvanized conduits under floor to the phono amplifier

The noise is louder if i run in air outside of the conduits.  When in conduits only 3 feet at either end is exposed.

does anyone have any suggestions?  read that there are braided copper sleeves could try with exposed part?  use tinned copper tape?   or is there something else going on?
128x128jricci
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cleeds
5,957 posts
 
jricci
Would running cables through a braided sheild in the conduit work?
Before undertaking additional work, you should try correcting your improper electrical safety ground that is " independent from rest of house " and be sure that it is properly bonded to the neutral bus bar in your electric service panel.
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jricci OP
10 posts
 
It is
Done by licensed electrician
erik_squires
16,119 posts
 
Again, need to know if this problem exists with short cables, and exactly how they are constructed.

There are two types of shield: Braided and foil. Foil is 100% coverage, braided around 80% I believe.

All my cables are 2 conductors plus shield, never have a noise pick up problem.

Best,

Erik
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