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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
erik_squires
16,046 posts
 
I just noticed that the Coincident statement line stage does in fact include balanced outputs built in.

One last thing, running audio cables in metal conduits can roll off the highs due to capacitive coupling.
jricci's avatar
jricci OP
9 posts
 
The noise occurs if interconnect connected to amplifier

Doesn't matter if
-connected to phono amp
-phono amp on or off
-phonoamp volume up or down
-phono or bypass input selected


erik_squires
16,046 posts
 
Jricci,

But it doesn't happen if you use a short cable?

Erik
rbstehno
1,430 posts
 
Try shielded cables for your phono connections. That's what I use and they are dead quiet
jricci's avatar
jricci OP
9 posts
 
Would running cables through a braided sheild in the conduit work?


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