Does digital optical audio output "sleep"?

Can anybody shed some light on this? It is very annoying since, as mentioned above, my audio system will produce static noise when there is no source present.

Strangely, this does not happen when I'm using Windows under Boot Camp...

I have a very similar problem, it does appear that on the MacMini at least the optical output goes to 'sleep'. Can anyone suggest a way to disable this 'feature'?

I've also been having this problem with my Mac mini (2009 version). Static/crackle sound over digital connection when the audio has been idle for a short while.

It reminded me of an old problem that some PowerBook G4 users had several years ago, where the audio hardware would go to sleep to save power and there would be a delay while it woke up. I remembered that there were a coupe of utilities created to remedy this problem by playing silent noises at short regular intervals.

I tracked down these utilities - KeepSoundAwake and SoundOn. Someone mentioned that SoundOn used a whopping 1% of CPU and showed a Dock icon, while KSA usage was usually 0% and had no Dock icon. So I decided to try KeepSoundAwake.

Here is a link:
http://mrfeinberg.com/KeepSoundAwake/

So far so good. I've been crackle-free for the last several minutes since starting up the program. This is a pretty ancient application (last update was a fix for 10.3 compatibility), so there are a few things to be aware of. I now have this one non-intel-native app running constantly, which is sort of a bummer - but with 4GB, I'm not too concerned. The PrefPane that comes with it will not run at all since it is not intel-native, but the default settings are fine so that's not really a concern either. You do need to make the app a startup item so it will be running all the time.

If I encounter any problems with using KSA with my setup, which includes running some multi-channel audio through Plex, I'll report back here.

I do wish Apple would officially address this issue so we wouldn't need to use a 7-year-old hack!

Well now the crackling/static sound is back, so I guess this didn't work. I may try SoundOn later, if I do and it works I'll post here with that info.

Yes, the Mini's optical output shuts off when inactive, the way it was designed to. Any digital input is supposed to mute when it loses carrier sync, so there ought not to be a problem. What kind of amplifier are you using? Is it working right?

A possible solution would be to run some sound application like Audacity or Audio Test and have it continuously play a very quiet very low frequency inaudible tone, like 20 Hz at -50 dB. That would keep the output awake. Hopefully it wouldn't confuse a Dolby or other multichannel decoder. My Sony preamp mutes properly, but I have Audio Test putting out 20 Hz at -70 dB while iTunes is playing, and it seems to be working. However when the Mini goes to sleep, the output of course goes off. There may not be a 100% solution.

I'm using a Denon 3805, and it's working fine with all other devices. My Motorola HD cable box, PS3, X360, PS2 and a couple of different DVD players have never exhibited this problem.

I know what you mean with the receiver turning off the sound when it loses sync. When my DVD player changes titles on a disc, or when the PS3 leaves the system menu and boots a game, the receiver display indicates it's no longer receiving/decoding anything and mutes. This does not happen with the Mac mini.

It seems like the Mac quits giving the output any signal/sound, but does not actually turn it off.

Why are you outputting that constant low-freq tone?

The constant low frequency tone is inaudible but it keeps the Mac's output active, putting out a signal. It is a substitute for those other "keep alive" apps. Just an idea you could try.

My Sony indicates no input signal when the Mini's output goes off. Mine is behaving differently than yours, it seems. No audio app running, no carrier, no light on the Sony's panel. Start playing something in iTunes, and the 44.1 or 48 KHz light comes on, and the Sony un-mutes. Then if i pause iTunes, after 15 seconds, the Mini shuts off the optical transmitter, the Sony mutes, and the red light in the fiber optic cable goes out.

I'm running OS 10.5.7 with the latest updates on a new (early 2009) Mini upgraded to 4GB RAM and 500GB HD.

Could it be that you have some strange app running in the background making noises? When your Mini is supposed to be quiet, does the Denon indicate it's still getting a signal? Weird.