[macrojack]

My son has a MacBook Pro. He runs a cable out of the headphone jack into a passive preamp where it goes to an NHT S-oo sub and then to a pair of M-oo monitors. When the MacBook is the source, there is a cyclical rotating sort of sound coming out of the speakers. If he pulls the plug out of the laptop and plugs it into his IPod Touch, the sound is not there anymore. Can anyone suggest anything about the cause and/or cure of this?

[jtwrace]

Probably the switching power supply.  If he just disconnect the power and runs off the battery is it still there?

[macrojack]

Yes. That was my first thought when wondering why it happens on laptop but not IPod. Battery vs. house current seemed like a probable explanation but the laptop does the same either way.

[Atlplasma]

Is the sound present all the time or only when running iTunes? Also, if using iTunes, how is your music encoded?

[bunnyma357]

If you listen to the MBP with headphones is the sound there, or only when going to speakers?


Jim C

[macrojack]

Is the sound present all the time or only when running iTunes? Also, if using iTunes, how is your music encoded?

He's in Durango until tomorrow night and the laptop is with him. I think it is only with speakers.

[macrojack]

Is the sound present all the time or only when running iTunes? Also, if using iTunes, how is your music encoded?

I'm not sure of the answer to this question. I'll put him on line tomorrow to tell you.

[macrojack]

Dewey's back and we have discovered that the noise is only present when the printer cable is plugged into the MBP. Don't know why that's a problem but we know how to avoid it even if we can't figure out a fix. Thanks for trying to help. And if anyone can suggest why the printer cable should matter, we're all ears.

[skunark]

Dewey's back and we have discovered that the noise is only present when the printer cable is plugged into the MBP. Don't know why that's a problem but we know how to avoid it even if we can't figure out a fix. Thanks for trying to help. And if anyone can suggest why the printer cable should matter, we're all ears.

Sounds like a good excuse to pick up a wireless print server (i.e. airport express) and call it good.   

[macrojack]

He's in touch with my wireless monochrome laser but for some reason he plugs his old inkjet in anyway. Maybe this discovery will break that habit.