When you say you bring IC to above floor, the same IC?
Or just another one.
I will assume you actually bring the same physical interconnect up.
Then you have some wierd stuff in the floor.
Something is causing a field of some kind in there under the floor. Could be even something in ground under the house?
A way to cut the field would be to run a armoured cable sheath (like used for A/C armoured wires) and run that under the floor with the interconnect inside. and ground that shield to the A/c ground.
that would cost about a buck a foot.
If that did not work, or only partially then:
Then if you can use a balanced connection, you should. A balanced connection will (Hopefully) not be affected by that.
I would see if you can borrow a suitable cable from a cable place or your dealer, and try it, Even if you can borrow several shorter ones and chain them together just to try out if it cuts the hum. Then you can buy a correct one if it works.
Then even both the armoured cable shield ,and the balanced wire.
If you use it for one channel, and it works, i would do it for both (the balanced wires).
No guarantee.. but other stuff to try
Also: Non contact voltage detector: From Amazon: Greenlee GT-16 ($22) it goes off if a electomagnetic field is around, or something is spewing out a field. IF you can actually get under (a basment? or crawlspace?) and use the detector and it will go off if a field is present. it may be just in one spot. Or a big area.
http://www.amazon.com/Greenlee-GT-16-Adjustable-Non-Contact-Detector/dp/B001QIJOW0/ref=sr_1_1?ie=UTF8&s=hi&qid=1306389698&sr=8-1
Well worth checking out.
Or just another one.
I will assume you actually bring the same physical interconnect up.
Then you have some wierd stuff in the floor.
Something is causing a field of some kind in there under the floor. Could be even something in ground under the house?
A way to cut the field would be to run a armoured cable sheath (like used for A/C armoured wires) and run that under the floor with the interconnect inside. and ground that shield to the A/c ground.
that would cost about a buck a foot.
If that did not work, or only partially then:
Then if you can use a balanced connection, you should. A balanced connection will (Hopefully) not be affected by that.
I would see if you can borrow a suitable cable from a cable place or your dealer, and try it, Even if you can borrow several shorter ones and chain them together just to try out if it cuts the hum. Then you can buy a correct one if it works.
Then even both the armoured cable shield ,and the balanced wire.
If you use it for one channel, and it works, i would do it for both (the balanced wires).
No guarantee.. but other stuff to try
Also: Non contact voltage detector: From Amazon: Greenlee GT-16 ($22) it goes off if a electomagnetic field is around, or something is spewing out a field. IF you can actually get under (a basment? or crawlspace?) and use the detector and it will go off if a field is present. it may be just in one spot. Or a big area.
http://www.amazon.com/Greenlee-GT-16-Adjustable-Non-Contact-Detector/dp/B001QIJOW0/ref=sr_1_1?ie=UTF8&s=hi&qid=1306389698&sr=8-1
Well worth checking out.