RCA to speaker wire?

Question

I have a receiver with RCA sub out and a powered sub with RCA in. I already have speaker wire in my wall so I spliced RCA ends to the speaker wire. It works but I get a slight hum from the sub when not in use. Any suggestions?

Answer 1

What you're describing is EMI (Electro-magnetic Interference)

The best way to do it is to ground the wire. That should eliminate the hum.

If you've ever seen Car Audio RCA wires, there's a little third wire that is attached to it. This actually grounds the power wire. RCA cables automatically ground when you plug them in, but you now have an incomplete ground since you cut the ends off one side.

The only way to fix this is to complete that ground. on the ends  that you cut, attach a small piece of wire to the braided shield and ground it to anything that's metal that would go to the floor.

Answer 2

Well.. You dont use speaker wire for line-level signals.

Look - if it comes from an RCA jack - the signal are line-level.  You must use an RCA cable made from Coax.  This means:

- Center wire that carries the signal surrounded by white dielectric.

- Outer shield of foil/mesh/both.  This is tied to your 0.00 volt ground.  This protects the center wire from stray electrical noise.

These line-level signals on the center wire carry no power. They are weak and if you dont shield them - any stray electrical signal will clobber them.  This is why you use RCA/coaxial cables.

Slapping RCA plugs on speaker wire will let it pick up all kinds of electrical noise - and the most common is 60 hz which is what you have.  And your subwoofer is amplifying it.

Go get some CATV coax with "F" connectors attached and two "F-to-RCA-Male" adaptors from Radio Shack.  Use this to make a long sub cable and hook the sub up this way to see if the hum goes away. If so, use the CATV coax or get a long RCA cable.

Answer 3

It is a noise issue. The solution is to replace with the correct cable.