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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > Sound In/Out on an iMac + Connection to Stereo Receiver

Sound In/Out on an iMac + Connection to Stereo Receiver
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gwebby
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Dec 6, 1999, 04:13 PM
 
I would like to use the line in/out mini jacks on the side of my rev C iMac to connect to my Onkyo stereo. However, when I hook them together I get a low frequency humming noise from stereo when accepting input from the iMac and the same noise from the iMac when getting sound from the stereo. I have been advised that this is possibly due to the audio pre amps in both pieces of equipment, i.e. the hum is the result of an already amplified signal being amplified again. The iMac sound capture works fine if I directly plug in my CD player but this is entirely too limited. Any suggestions?
     
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Dec 6, 1999, 05:24 PM
 
I've had this problem with my iMac DV and have yet to find a solution. The problem just seems to clear itself up after a while (anywhere from a couple minutes to an hour) if the device stays plugged into the iMac.

Also, make sure that the cable that you're using is a quality one... that could be contributing to the noise. If the cable is very long, make sure it has extra shielding.
     
MacPhan
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Dec 6, 1999, 10:04 PM
 
Misha may be right... but my iMac DVSE has a mic input, not a line input. The difference is great because, as you said, the line input is much higher impedence. You should be able to by a cable at Radio Shack and elsewhere that would "pad" the signal, reducing the line level output of your stereo to a mic level. Let us know if that works.

HTH,
Rick
     
qvilorio
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Dec 9, 1999, 12:07 PM
 
Where can I get this special cable online?
     
gwebby
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Dec 12, 1999, 11:56 PM
 
Well folks, I solved the problem. Turns out that the hum was caused by a grounding problem between the imac and the stereo. All I had to do was gound both pieces of equipment to the same "sorce" - in this case the screw on the respective power outlets and the hum disappeared. I got the idea while paging through the manual for the stereo and, looking at an old Apple TIL for a fellow that had a similar problem on an old PM7100. A light clicked and I went "I wonder if..." and it worked!
     
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Dec 13, 1999, 06:05 PM
 
How exactly are you grounding both systems?

Also, I noticed that when I plug the stereo mini plug into the iMac DV's sound out port that I get the line noise, but if I plug it into the microphone port I don't.

Ideally I'd like to be able to plug it into the stereo out port with no line noise (that way the sleek appearance of the iMac isn't ruined by the black stereo mini jack), but for me, it's always function over form...
     
gwebby
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Dec 14, 1999, 12:17 AM
 
To ground the stereo I ran a wire from the grounding post on the back of it o the screw on the electrical outlet wallplate. For the iMac I bought one of those 3 prong to 2 prong power adapters that gave me a grounging connection for the third prong and then wire that to the wall plate.
     
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Join Date: Dec 1999
Location: Perth, WA, Australia
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Dec 14, 1999, 11:33 PM
 
Mind you guys don't go and electrocute yourselves doing this. It's times like this its good to live "downunder" where almost all electrical equipment (such as computers) have a grounding wire as part of the plug. Saves all that "screwing" around. (Bad joke I know)
     
Ron
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Dec 15, 1999, 09:07 PM
 
I avoid wires all together. I use a small FM transmitter to feed the audio signal from my iMac to my FM stereo. You can find these at electronic hardware stores for around $15.
I'm always replacing AA batteries, but the sound is really great!
     
   
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