How can I eliminate "line noise" or "hum" from my home audio system? I have a G4 and a DVD player plugged in.

Question

The Mac G4 is connected to the amplifier via a USB audio device that converts to RCA output, then runs into the CD input of the amp. The DVD/VCR combo unit connects to the VCR input on the amp. I have a single RCA line running the video signal from the "monitor" output of the amp into the TV. I get the hum sound on the CD channel, as well as a series of moving vertical lines in the TV picture itself while playing a DVD. If I disconnect the USB device, the noise disappears. Likewise while playing music off of the Mac G4, if I disconnect the RCA line into the TV, the noise disappears. But when they are both connected, I've got the noise. What is going on here?

Answer 1

Another source of hum noise is ground loops in your wiring. There are several things you can do to help avoid this. One is to get better cables, as the other poster suggested, but specifically get cables with better shielding. Most RCA cables are poorly shielded; better shielding may result in less hum.

Another is to check the wiring of your house. By this I mean make sure that all the outlets that things are plugged into are three prong grounded outlets. Also make sure that the ground pin (the round hole in the outlet) has a good electrical connection to ground. You can do this with a voltmeter and ohmmeter:

1. Measure voltages on your outlet: use the voltmeter to measure the voltage between the two slotted holes and between each slotted hole and the round hole.

2.Figure out which slotted hole is at the same voltage (0 volts) as the round ground pin. This is what is usually connected to the white wire inside the wall.

3.Turn the meter to resistance/ohmmeter mode. Measure the resistance between the ground pin and the slotted hole you found above. This resistance should be near zero.

4.If you have some alligator clip wires, use them to extend the reach of your ohmmeter and measure the resistance between the ground pins of the different outlets you are using.

Another thing that can help is if you are using power strips is to put closely connected devices on the same power strip. i.e. plut the G4 and the USB device into the same power strip, and the CD player too if possible.

Above all, if you have anything with a 3-pin plug which you are adapting to a two-pin power plug, remove the adapter and use a true three pin outlet.

Answer 2

sounds to me you have a bad cord probably one of thre ones that effects the hum when unplugged. TRy a new or better cord. Also you can try moving the amp away from the computer, some times the em fields produced by the amp will effect the power running thru the cables. You can also check the amp to see if it puts out a 2 ohm signal or a 4ohm signal. Useing the proper corisponding cable will help, ie 2ohm cable for a 2 ohm output. Or maybe check to see if you can ground the amp some how, some amps have a ground connection on them somewhere or thr using a 3 prong grounded cord on the amp cpmputer and dvd player. Electronic have a mind of there own sometimes hope these tips help. Also try moving sound cables away from power cables.

Answer 3

One that’s in serious need of a face-lift. Actually it isn’t all that bad. I have a surround sound system in my basement that’s hooked up throughout the house. Also got a Sonicbridge so I can play Internet radio through my amp. It’s just a pain in the *** having to always go downstairs to change a station or disc (terminal laziness). Therefore, my main music refuge has been the iPod and the automobile. And since the computer has emerged as my premier listening outlet between satellite radio, Internet radio and iTunes, I need to get some new computer speakers like yesterday.

Answer 4

I had a similar problem and I fixed it by going out a USB2 to Creative Systems Soundblaster and then back into the amp via a digital cable.

Answer 5

trying to operate too many electronic devices at once,,interfering with each other,,if possible put some distance between components and plug into different outlets,this includes speakers too close togeather..hope ive been some help..good luck..