I know this is a little OT, but I've given up trying to get help in the 'normal' forums, so I trying here! My iMac 2011 audio goes via the optical cable to a receiver. After 30 seconds of no audio, I can hear a click/pop as the audio shuts down. Then, any sounds miss the first second or so when the audio is waking up, so that means in the case of system sounds I miss them completely. Very annoying. I've tried various apps like KeepSoundAwake (doesn't work on Intel), AntiPop (seems to lock the audio after a while) and another that I can't remember. I've seen lots of older posts on this especially to do with MacBooks, but no solutions. Only happens on the digital output as if I disconnect the optical cable, the problem doesn't occur through the internal speakers. Any ideas appreciated.