Device: iMac 27" late 2010

Here's one..When I plug in an optical cable to my iMac with an adapter it worked fine for a while now the red light on the optical cable is very faded. But only on the iMac, it works fine on the other pc's and things in my house. When I plug it into the iMac, it recognises it but there is no sound.. I seen this problem on a lot of forums but never any answers. No worries if you don't know.

When you plug the optical mini-jack into the Mac, it should detect that an optical connection is present. To verify, go to the Apple menu > System Preferences > Sound > Output. It will probably list optical as the output or show it as a selectable option if this is not the case. The device you are using may require optical to be manually selected as the input source. In some cases the device may also require the sample rate and/or the clock source to be selected as well. If that’s the case, set the sample rate to be the same as your audio file/source that you will playing from the Mac. Set the device's clock source to optical (digital input) if necessary. Checking the device's manual is the best safeguard so don't hesitate to do so.

Arguments can lean one way or the other so far as the technological advantages of Firewire vs optical vs USB. In any case, it’s best to keep the distance of the digital run from the Mac to the audio device as short as possible and use quality components (cable, adapter). Using the Mac’s output connector mutes the speaker playback on many, if not all, models. Since a mini-jack is a fairly fragile connection compared more robust options, it may be more susceptible to breaking or wear from constant plugging in and out to hear the speakers. If you are the type who switches to the speaker playback sparingly, this may not be a concern.