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
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.
It isn't clear what you mean by " course EMF like noise ." But the problem could be your ground, which you state is not shared with the rest of your house. In the US, this would be a violation of the NEC and is potentially hazardous. In any event, if it's an unshared ground ... to what is your system grounded? It sounds like it's not bonded to the neutral in your service panel, which would tie it back to the electric utility ground. That's your best ground, which of course is supplemented with ground rods as required by code.


I don't know the topology of your cable, but you could try swapping it end for end (turn it around). Some cables are grounded on one end only. It's probably a longshot, but I don't think it would hurt to try it.
Separate audio system ground independent of house ground

All audio grounds share single ground with no ground loops

Noise present when interconnect connected to amplifier input. No other connection impacts sound.  No effect of phono amp gain or power on