need help running audio line through a wall

[HamNCheese]

I'm looking to run a line level out the tape mon. output of my living room amp and into the tape mon. input of an amp in an adjacent room. To do this I have to pass cable through one wall, the rest of the cabling will run around the baseboard of the rooms. I tried using speaker wire with RCA jacks on either end but it picked up too much hum. Can anyone recommend to me what kind of cable to use for this? I read somewhere that CAT 5 computer networking cable works well for this, has anyone tried that?

This doesn't need to be a super best high end sound quality kind of thing, I just want a decent, hum-less signal.

[RickH]

For line-level unbalanced audio you need shielded cable, over 25 feet you will need a better quality low-capacitence shielded cable to not lose high frequencies. Some single conductor microphone cable is a good choice, Belden is a good brand. Or just buy some long interconnects cable with RCA jacks.

Even with sielded cable you may get hum if the devices being connected are at different ground potentials. Even 2 devices plugged into the same branch circuit in different rooms (almost always) have varying impedance to ground (by a few microvolts). This difference will cause a small AC current to flow in the shield itself, (electricity flowing from the higher impedance weaker grounded device to the strong grounded device). That 60Hz AC current in the shield, being only a few microvolts is then magnetically "induced" into the center conductor if the interconnect cable and becomes the hum you hear amplified by your audio equipment.

First go to Radio Shack or order a shielded audio interconnect cable of the length you need with RCA connectors. Try that. If it still hums, then you will have to "lift the ground" on one end or the other of the cable, (so the shield is only grounded at one end). This will still leave you with a fully grounded/shielded interconnect but just one that has no opportunity for stray AC to flow and so no hum.

You can create a ground lift cable by cutting off one of the plugs and replacing it with a new plug, but DONT solder or connect the shield on the new plug, just the center conductor. Leave the other plug alone. Connecting the 2 audio devices with this modified cable should alleviate the hum.

HTH Rick