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jumpenpro's avatar

How can I get rid of humming from AUX cable?

Asked by jumpenpro (16points) May 21st, 2011

I have a realy long AUX cable that i use to connect my PC or my Ipod to my hi-fi system and i keep getting interference from it. I constantly hear a loud humming or rippig sound and sometimes i even hear people talking faintly:) Is there something that i could build for the cable that get’s rid of the interference. I still have a bunch of diodes and capacitors and stuff like that from a physics class if someone knows there way around that stuff. What could i do to fix this?

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6 Answers

gasman's avatar

You’re picking up some combo of 60 Hz AC hum and RFI (radio frequency interference) making its way into the amplifier electronics. Try some of the following:

(1) reduce the cable length. Shorter cables are less prone to interference.

(2) re-route the cable. Especially eliminate any runs parallel to other cables—better to have them cross at right angles. Sometimes just re-orienting one section can make a difference. The cable is acting as an antenna—may be sensitive to position and orientation.

(3) Make sure the cable is shielded (coaxial, not just a pair of parallel wires) and grounded. The shield should make a metal-to-metal connection in back of your equipment.

(4) They make snap-on ferrite chokes that are like little iron donuts that go around the cable. These can sometimes reduce RFI.

(5) If you can actually hear talking then it’s either a radio station or something like a CB or walkie-talkie in the vicinity. If you can determine WHO is broadcasting—and if they are a local source, not some distant station—then they might be in violation of FCC rules & you can nail them (by making the government shut them down) once you identify them.

In theory you could fashion your own filters from resistors, capacitors, and inductors but in practice it wouldn’t be easy and most likely would worsen rather than improve the situation. Diodes are probably not going to work either, & might make things much worse. Hope any of this helps.

LuckyGuy's avatar

GA from @gasman
Make sure the shield is attached to ground at one end only. You don’t want to form a current loop.

YoBob's avatar

You can try wrapping it through a circular magnet a couple of times (one of those disk shaped jobs with a hole in the center).

jumpenpro's avatar

I tried moving the cable and that worked but I have to keep readjusting it. I’m gonna try some of the other things you guys suggested and if that doesn’t work then i’ll just switch to a shorter cable. Thank’s for the great answers guys:)

gasman's avatar

@worriedguy Yes, ground loops are a source of induced ac hum, especially if the two ends of cable are far apart electrically.

@jumpenpro Another thing I thought of is a bad connection at one or both ends of the cable—you didn’t say what kind of cable it is. If the connectors are oxidized / tarnished or mechanically loose, then a bad connection translates into high impedance, which makes the whole thing more susceptible to noise & interference.

Try plugging / unplugging each end a few times, or twisting the connectors together if it’s of a type where that’s possible. Use fine sandpaper, emery board, or wire brush to make the exposed metal parts, where contact is made, as bright & shiny as possible. You shouldn’t have to do this more than once every few years unless you live near the ocean.

A broken wire could give similar symptoms, where it suddenly gets better or worse when you wiggle the wire a little, usually near one end.

wezdemez's avatar

Re routing my aux cable away from my laptop charger fixed my buzzing! Was so annoying having that constant buzz but not having my cords touch each other worked. Maybe an issue with the mix of ac and dc power, or just power in general.

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