Imac 27 inch audio

Question

Level 1

0 points

Imac 27 inch audio

I have a problem with my imac 27 inch. when connected to an external audio device i hear the mouse scrolling in the speakers. Even if I mute the audio out. There is like an annoying static sound coming out of the speakers even when the computer is on idle. Does anyone have this problem, and how can it be resolved? Hope someone can help me out.

imac 27 inch, Mac OS X (10.6.6)

Posted on Jan 12, 2011 9:23 AM

Reply

Answer 1

MandiM

Level 1

0 points

Jan 15, 2011 7:43 PM in response to FCC123

I bought my husband a 27 inch iMac for Christmas, and we are having static issues with the speakers too. We don't have anything plugged into it -- just running it as it came out of the box, but there is still static coming from the left speaker. It isn't loud (it has nothing to do with the volume as it sounds the same whether the volume is on mute or up all the way). It's just really annoying for something this expensive.

Reply

Answer 2

FCC123 Author

Level 1

0 points

Jan 18, 2011 4:08 AM in response to MandiM

I tried plugging in the optic cable and it seemed to have stopped the static. you can still hear if you put your ear close to the speakers but it's barely audible. the bad thing about the optic cable is that you have no volume control from the computer itself. the think the static we hear is that the audio is picking up the sound that the hard drive makes. I'm gonna try to call apple care and see what they say. Im they are going to say there is nothing they can do about it, but it's worth a try. I doubt they're gonna exchange my computer. I'll put up another post and let you know what they say I should do.

Reply

Answer 3

Feb 1, 2011 3:48 AM in response to FCC123

I'm getting the same problem from my new iMac 27" which is incredibly noisy through an amp and speakers. Let us know if you find a solution...

Reply

Answer 4

Gator00

Level 1

4 points

Mar 19, 2011 4:40 PM in response to FCC123

Apple support told me this is the first they had heard of this problem, and lo and behold there are indeed others. I have been conversing with them for over three months, they replaced the main board and are now considering replacing the power supply. One tech told me I needed to purchase a UPS to solve the problem, it didn't.
The Setup:
iMac 27" headphone jack via mini din (1/8" plug) to Audio rack (mixer, EQ's, compressor, power amps, near field speakers, Digirack 002 with Protools 8 and M-Audio octane hooked back to iMac via firewire) all equipment (printer, modem included) powered by two Furman PL-8C power conditioners into the same wall outlet (the same 120v breaker)
The Symptoms:
White noise that changes characteristics (pitch, intensity) with what is displayed on the screen or what the iMac is doing such as using the cursor to dispay and hide the dock, a web page with flash and then minimize the window and the noise goes back to the original sound or a external HHD being accessed. It is almost as if the video card is emitting too much electro magnetic whatever's on the sound module thing-a-ma-jig. You know what I mean.
The troubleshoot:
Suspected a ground loop issue, hence the Furman's as they are suppose to arrest that. Ran and extension cord from the bathroom GFC plug with only the power amp and iMac, swapped out all cables, power amp, and my G4 powerbook which by the way did NOT exhibit any symptoms.
Possible Solutions that I (not Apple) came up with:
Lift the ground on the iMac (not a good idea), switch over to digital optics (if only Apple would supply input/output specifications so that I don't have to try to become an expert in protocols PMC DVD yada yada...), or use a ground loop isolator adaptor (which will reduce the noise floor but not remove the problem) or wait for Apple to find a solution, which I really hope they do as I set up my system how I like it and would prefer not to have to spend more money to change it. Any one interested in buying a slighty used UPS?

Reply

Answer 5

Mar 19, 2011 10:05 PM in response to Gator00

I had this problem with my brand new iMac and I called apple, they acted like they've never heard of it. Of course. Didn't happen with my old iMac.

I bought a cheap 5$ power strip and bent the ground plug on it, plugged my rokit8's into that and magically all the ground static was gone....

Reply

Answer 6

Gator00

Level 1

4 points

Mar 19, 2011 11:12 PM in response to FCC123

BNun, sounds like you lifted the ground, a safety feature, I'm not sure I want to do that.

Reply

Answer 7

Mar 20, 2011 12:23 AM in response to Gator00

I'm not saying anybody has to do it, but I did, and it worked.

I am not terribly afraid of getting electrocuted by my krk's "stray voltage" anyway...

If a fault occurs in the electrical device there is a possibility it could energize metal parts of the device that a person could touch. That would result in a potentially lethal shock to the person touching the device. With the "EGC" (ground) connection any fault current is immediately drained off, under normal conditions, before it can become a danger to people.

Reply

Answer 8

Jun 18, 2011 9:01 PM in response to twistatech

Hi All,

I've had this problem since I got my iMac. I've been searching all around to find a solution to this problem because it is very frustrating, especially when watching quiet films where the noise is easily heard in the background.

This is the exact noise I was getting

http://www.youtube.com/watch?v=VTucTycgtnk

To me it always sounded like HDD noise somehow transferring through the soundcard and on to the amp. However, I recently installed an app that shows HDD use. Interestingly the noise and the HDD do not appear to be directly associated with each other. For example, scrolling through a website made little HDD usage but the noise was loud. Transferring a file from USB to HDD had great usage but the noise was quiet.

Now. . . .I used to use a Laptop through a DJ system and I had a similar noise when using that. The solution was to unplug the laptop from the mains. This proved the issue to be a problem with the ground connections from the mix/amp and the laptop. Technically it's called a ground loop.

THE SOLUTION

Whilst disconnecting the ground cable from the iMac is a solution it's far from perfect or even safe.

This issue has been around for many many years, just not with apple products. I believe a new / cheaper power pack in the new iMacs has caused this problem as it does not reduce effectively ground looping.

In a few hours I am going to purchase a ground loop isolator. It sounds expensive and complicated but it really isn't. It costs around £15 from the shops and as little as £5 online. It simply plugs inline into the phono connections between your mac and amp.

http://lmgtfy.com/?q=ground+loop+isolator

It should work, i'll report back if it does.

Nick

Reply

Answer 9

Jun 19, 2011 1:26 AM in response to FCC123

Running a mini jack to double RCA lead => amp, you're running an unbalanced cable. There is no shield wire to isolate the cable from electrical interference which is transmitted via induction. The digital optical out is much cleaner because it operates via an optical interconnect and doesn't suffer the same inductive effects as the unbalanced audio circuit.

A ground loop isolator should clean up your signal as mentioned.

Reply

Answer 10

Jun 19, 2011 2:48 AM in response to Leddy Mountbatten

^^This is a fair point^^ However, I have just swapped my 27Inch i5 around with my older iMac duo and there is no problem - no buzzing, no cracking - nothing. This proves that there isn't a problem with my setup, amp or cables. The problem truely does lie with something in the 27inch that is causing a nasty ground loop.

Reply

Answer 11

Jun 19, 2011 3:04 AM in response to NickElsby

Agreed Nick. It's possible Apple have made some engineering decisions that have adversely affected the audio performance of the new iMacs.

I have a similar problem on my MacBook Pro 17" which is the model before the latest one. A $3000 AUS Pro machine that is not properly shielded. A little disappointing to say the least. My iMac 21" Core 2 Duo had the same problem.

Best Wishes.

Reply

Answer 12

Jun 19, 2011 5:03 AM in response to Leddy Mountbatten

Okay, I've fitted an isolator. The absolute tiniest of noise still remains, but it's only audible when my 50W amp is turned up to full, previously the noise at that volume level was huge. There may be a small of reduction in bass quality to the signal but it's not what I would call noticeable. I spent £15 on the isolator, high end DJ ones are available for a little more. However £15 to fix a problem that was causing me a headache is pretty good.

Apple, I do feel that you should be fixing this problem for us.

Hope this helps guys.

Nick

Reply