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Author Topic: Computer noise in monitors  (Read 3565 times)

Julia123

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Computer noise in monitors
« on: May 03, 2011, 11:16:34 am »

I have some new monitors for my home recording studio that are "shielded for a/v use".  There is no ground hum but a sound that reminds me of how SMPTE time code used to sound.  It happens when files are loading on my iMac and they also pick up mouse movement and screen drags etc.  I've moved them a few feet away, no difference.  Volume down on computer, no difference.  Move around audio cables plugged into the speakers, no difference.  Wireless or non wireless mouse, no difference. Lift ground, no difference.  I've turned the volume control on the speakers themselves way down, which helps a lot but when I put the level where I truly want it, it is very noticeable. Is this normal?   Any ideas on how to fix this?  It is very background but enough to bother me.  Thank you for any suggestions! 
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Bubba--Kron

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Re: Computer noise in monitors
« Reply #1 on: May 03, 2011, 02:44:06 pm »

Just a wild guess, is there a cordless phone in the room?
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Julia123

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Re: Computer noise in monitors
« Reply #2 on: May 03, 2011, 04:21:27 pm »

No cordless phone.  It is definitely the sound of the computer activity.  When the mouse drags a window, the speakers buzz.  When a file is copying, it sounds like SMPTE time code.  If there was a cordless, would that cause this "amplification" in some way?  I live in a condo so maybe my neighbor has one.
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Dale A.

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Re: Computer noise in monitors
« Reply #3 on: May 03, 2011, 04:32:39 pm »

What are you using as your I/O?
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Julia123

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Re: Computer noise in monitors
« Reply #4 on: May 03, 2011, 05:06:32 pm »

It happens whether I use my Apogee One Stereo out or directly plug them into my computer output.  There is also a constant tiny bit of static when the computer is on at all.  When I shut it down, the speakers are nice and quiet.
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Gio

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Re: Computer noise in monitors
« Reply #5 on: May 03, 2011, 10:54:28 pm »

I get this too. Weird...
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Graham Duncan

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Re: Computer noise in monitors
« Reply #6 on: May 04, 2011, 12:07:15 pm »

Sounds like hash from the iMac power supply getting into the audio.  Things I'd try: 1 - ask Apogee re: the One.  2 - find an optical cable for the iMac output and run into a borrowed external converter to see if that stops the noise.

Good luck,

Graham
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jaykadis

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Re: Computer noise in monitors
« Reply #7 on: May 04, 2011, 02:17:17 pm »

I get that type of noise on my G5's analog outputs, but not through the Mini-Dac connected via lightpipe, so I would suspect a ground-related issue or power supply noise.

Dinogi

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Re: Computer noise in monitors
« Reply #8 on: May 10, 2011, 05:11:00 pm »

Had the exact same issue with an unbalanced soundcard from M audio in a HP computer. The mouse noises could be removed by moving things around. Never did get the weird computerized clockpulsey noises out of the signal until I switched to a balanced card. Also M audio. Is your Apogee interface balanced?
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Julia123

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Re: Computer noise in monitors
« Reply #9 on: May 12, 2011, 07:41:42 pm »

It happens when the Apogee is completely disconnected.  I am just using 1/4" to mini stereo though.  Should I try using balanced cables?  (I don't have any anymore).  I'm not sure about trying an optical out since my Apogee, which I want to use in the long run, connects by usb.
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Dinogi

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Re: Computer noise in monitors
« Reply #10 on: May 14, 2011, 07:40:58 am »

  Volume down on computer, no difference.

This makes me think theres something not right about the speakers. If the nasties are heard even with no output from the source, I'm thinking it must be an RF problem.
The balanced issue may not have anything to do with the computer or sound device. Here's my theory for what it's worth. If your speakers are designed for balanced +4 connection and your using two wire -10, there are two things happening. One, your gain has to be turned up to compensate for the lower level, which will bring up noise that would otherwise be too far down to hear, Second, The speakers being hooked up unbalanced may be turning the wires into an antenna and your speaker into a receiver. OK thats my best shot, but what do I know.  I'm just another home recording hack trying to keep his own stuff running.
old uncle dino
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boggy

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Re: Computer noise in monitors
« Reply #11 on: May 14, 2011, 11:10:28 am »

......Should I try using balanced cables?.......
Balanced outputs AND balanced cables are good idea.


Regards,
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Andrew Sweeney

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Re: Computer noise in monitors
« Reply #12 on: May 15, 2011, 07:18:34 am »

I had a similar problem which ended up being nothing to do with a ground loop but my intel i7 and ex58 motherboard. I cured it by disabling C1E and E1ST in the BIOS. It was to do with the processor speed-stepping. I am not sure if there is a similar solution with your iMac (does it use a new Intel processor?). Maybe this thread will help:

http://forums.anandtech.com/showthread.php?t=302995

Cheers,

Andrew
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