Imac 27 inch audio
imac 27 inch, Mac OS X (10.6.6)
imac 27 inch, Mac OS X (10.6.6)
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
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.
^^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.
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.
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
Imac 27 inch audio