iMac i7 Audio Issue

[Alan64]

This is the only acceptable solution I've come up with. It's worked for me for over a year now.

I don't have a sound problem on my iMac, but this device looks perfect for use with my electric guitar amp. Thanks for the heads-up.

 

[hashilli]

That high pitched sound you hear when moving your mouse around is a ground loop issue. And has nothing to do specifically with your iMac. My old PC tower did this as well. You need to ground your power amp or powered monitors with something like the HumX. you can get it from sweetwater.com.

I put that between my power amp's power cord and my wall socket, and the noises went away forever. I haven't had the problem in years since I got the HumX.

I am wondering why you put that noise gate adapter on your power amp's power cord and not the power cord on the PC. In my case, it is specifically the iMac that is the source. Any other device that I connect up, either USB to DAC to Monitors or 1/8" out to monitors, does not result in the same noise.

Maybe I am not understanding something, but I did not think it was the iMac sending noise out the power cord, through the strip or outlets and then into the monitor power cords into the monitors. I thought the iMac was incorrectly grounded internally and hence the noise coming across USB or 1/8" outs.

 

[slicecom]

I am wondering why you put that noise gate adapter on your power amp's power cord and not the power cord on the PC. In my case, it is specifically the iMac that is the source. Any other device that I connect up, either USB to DAC to Monitors or 1/8" out to monitors, does not result in the same noise.

Maybe I am not understanding something, but I did not think it was the iMac sending noise out the power cord, through the strip or outlets and then into the monitor power cords into the monitors. I thought the iMac was incorrectly grounded internally and hence the noise coming across USB or 1/8" outs.

My experience is the same. The iMac introduces all sorts of noise into the ground. Thus the iMac is the one that I isolate from the rest, and it works beautifully.

 

[jgullickson]

solution to your problem.

So here is the answer you are looking for....there is nothing wrong with your iMac. You are simply picking up interference from your speaker wires....if you are using a simple speaker (not self powered) and you are sending sound to it from some sort of amplifier you can use basic speaker wire...the signal out of the amplifier is strong enough that it will get to your speakers just fine. However if you are sending audio to a powered speaker this is called a line signal, and it gets amplified once it gets to the speaker. any wire is essentially an antenna, it will pick up interference from any number of sources...the longer the wire the more likely you will have issues. then once it reaches the powered speaker, any interference it has picked up will be amplified. The solution is simple, you need to use a properly shielded cable to block interference from getting mixed with your signal. If you want to learn more about this check out this article http://www.rane.com/note110.html . if you just want to get rid of your humming problem then use the proper cable (as shown in the above link) to connect an unbalanced output (your 3.5mm jack on your computer) to a balanced input on your speaker (XLR or TRS probably). You can make this sort of cable yourself with a little soldering, or go to any decent music store and buy a pre made one...something like this: http://www.custom-lynx.co.uk/3-5mm-stereo-2mxlr.html

Hope this helps, I experienced the same problem, however I work with audio gear professionally, so I knew how to fix it, I thought I would share the solution since I haven't really seen the answer posted anywhere yet....hope it helps.

 

[Shikasta]

Work around for external audio interference on iMac

G'day all, just joined MacRumors this minute so I can post my findings with this issue.

I'm running paired mono-powered speakers (Swan T200B) through a subwoofer (Swan H10). They are all connected to iMac via my trusty little Mieir Corda 3Move portable DAC running via 12 volts power.

Have increasingly noticed the 'static' and Magic Mouse movement sounds when I've had the sound system plugged in via iMac's USB port. Tried wrapping cable around ferrous donut...no change.

About an hour ago, after reading all that I could find about this issue, including here, I disconnected the USB cable and plugged a 3.5-3.5mm jack plug cable into the DAC's front input socket. BINGO...sound problems gone!!

BUT...I'm waiting for a new DAC, a John Kenny DAC32 which only has a USB input. We'll see/hear whether this little magic box manages to tame the iMac's USB gremlins.

For the time being I'm sticking with the 3.5-3.5mm connection. Great to hear the silence between the music again!

It's not a full solution but at least I'm enjoying the music again.

 

[Shikasta]

Playing with ferrous baluns

Update on last post.

I prefer the sound of my external speakers through the USB socket, they sound cleaner and bass sounds better defined.

So, after looking at radio interference solutions yesterday via Google, I woke up early this morning with the idea of using some ferrite baluns around the iMac's power cable. If you don't know what a ferrite balun is just Google it. You may even have some cables on your home theatre that have baluns already on.

So far I have attached one balun at each end. I've looped the power cable around one of the baluns just before the power strip. There is a noticeable reduction in static and Magic Mouse interference.

The last thing I did was to use another largish ferrite balun on the USB cable, looping around the balun 6 times. (That's as many turns would fit inside the balun!) Difficult to clip the balun together after but managed with some fiddling. The whole thing dangles at the back of my desk out of sight.

After listening close to speakers with no music playing there is still a very slight static/crackling sound but MUCH reduced from before using the ferrous baluns. Music comes across much cleaner and sound preferable to using 3.5mm headphone socket connection. I'm sure using a mini-optical connection would work well too but I don't have that option with my current setup.

It's certainly safer than cutting off the earth pin on the power cable!! 😱

Hope this is helpful to some others still looking for solutions to issue.

 

[casiel1969]

Problem fixed with $1 used Griffin iMic

I've had this hissing in my external speakers since getting my iMac. Tried everything. Figured it was a grounding problem. Just plugged in the Griffin iMic I had laying around and put the speakers into that. Problem fixed. No more hissing! Jesus wept... So there's a definite issue with the iMac and how it's handling audio out through it's mini plug.