Strange Radio signal from my speakers using Line Out on Mac Pro

I'm not sure why this would happen on a PC and not a Mac (better shielded hardware?) but I've scene the radio station thing happen on a number of devices. I've had headphones pick up a spanish-language station, and my roommate had a guitar amp that did the same.

I once asked someone why this happened. His explanation (no idea if its accurate) was that sometimes poorly shielded audio cables also have the unfortunate circumstance of also being the length or evenly divisible of the length of your typical AM radio wave length, making them perfect antennas. His suggestion was to add or subtract length from the cable. I never tested this, so I can't vouch for it as a solution.

I would also try putting the cable somewhere where radio waves are not likely to penetrate. Wrap it in aluminum foil, maybe?

I am having the same problem, and we are not alone. In fact, there is a whole thread on this (read down past the Airtunes stuff) on MacOSXhints:

http://forums.macosxhints.com/showthread.php?p=381194

To summarize, I am also getting an unwanted radio signal when I hook up speakers to the Line-Out output.

And it is most certainly coming from my Mac for the following reasons:

- When I plug another device (say my iPod) into the same line to the speakers, there is no problem (i.e. signal is not coming from my audio gear)

- When I isolate the Mac (disconnect all networking and internet connection) the problem persists

- I even bought a Stage 2 "Clean Power" Monster Power supply to filter any unwanted RF out of the power supply and that did not fix it

- the problem does not occur on the headphone out, only the line out.

Clearly something in the Line-Out configuration in the Mac Pro is not properly shielded and picks up radio signals. Anyone who has more info please contribute. I wonder if Apple is aware of this.

You probably have a radio station near you with a signal strong enough to cause "impact excitation". This is a term that an old radio buff used to describe what was happening to our stereos in the neighborhood. By using the Monster Power unit, you filtered the EMI and RF out of the AC line, but did not affect the RF in the air for your surroundings. When we do a forensic analysis of a cell phone, it is usually placed in a Faraday bag that eliminates any radio signals reaching the phone. You may be able to reduce the effect of the RF by placing your MP in an area of your office/home that is naturally sheilding the MP by wall construction contents, etc. We had a radio station about 4 blocks from our house that caused us fits. By your post, it appears that the signal is coming in through your speaker cable(s). Radio Shack or another company may have a filter assembly to fit between the jack and the MP. High-end audio shops may also sell this type of things

Michael

Just to throw fuel on the fire here, it has happened to me with a G4 with external speakers and also via a radio in my kitchen.
It doesn't happen all the time, but it sounds like morse code in a static-y version. Someone suggested it was caused by bluetooth, but not on my older G4 tower as it had no bluetooth.
Current Mac Pro has same problem with same speakers as old G4 did.
We have some heavy duty radio sources nearby and the problem occurs typically when they blast in our direction. I believe they also have a microwave device.

Thanks for the suggestions.

No, Forrest, it is not my speaker cables. If you read my original post I only have this problem when audio originates at the Mac line output ... any other device (or even the Mac headphone output for that matter) does not cause the signal to be picked up, so clearly it is not coming from my speaker cables, or the signal would be present all the time.

But I will see what I can do to better shield the Mac.

It could be Bill asking you to come back.

smile

The answer is simple get speakers with a better shielded cable.