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.
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.
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