iMac optical digital audio output not working

[ThundaDan]

Hi everybody,
been hanging around here for some time, but this is my first post. Here goes : i bought a 24inch iMac 2 days ago and i'm quite happy about it, except the optical digital audio output isn't working.
The sound is just fine when I use the iMac built-in speakers, and also when I plug in standard headphones. I AM using a toslink cable and a toslink-to-1\8 adapter, and I'm sure the problem isn't there because I also own a MBP, and the sound is just fine when I use the same cable-adapter-amplifier with it.
With the iMac, there is absolutely no sound, no whitenoise, no nothing coming out of the speaker. Also, when the cable is connected to the iMac and i go to preference-sound-output, it does say optical out !

Any help would be greatly appreciated, as it sucks to be unable to use 5.1 surround sound with this otherwise perfect iMac

Dan

 

[Cave Man]

Dan,

Try launching DVD Player app *but without a DVD in the drive*. In the preferences, is it set to output digital?

 

[ThundaDan]

No, it says : system sound output. But there is a scroll down menu and i could select digital out

 

[Leon Kowalski]

How long is the Toslink cable? Some iMacs seem to have seriously wimpy
optical outputs. There have been several reports of them failing to work
with Toslink cables as short as 10 feet.

If that's the problem, you might have better luck with a mini-toslink to
toslink cable -- straight thru, with no 1/8 inch plug adapter. Eliminating
the adapter will reduce light loss to an absolute minimum.

http://www.monoprice.com/products/s...udio+Cables+-+Optical+Toslink&keyword=toslink

LK

 

[Cave Man]

No, it says : system sound output. But there is a scroll down menu and i could select digital out

What is your source file of the 5.1 and is it Dolby Digital?

 

[ThundaDan]

1) my toslink cable is only 6ft long, however, I might try your solution if everything else fails (3$ ain't too bad)
2) My sources are DVDs, and they do have 5.1 and dolby digital

By the way, thanks for taking the time to help me guys

Dan

 

[Cave Man]

No, it says : system sound output. But there is a scroll down menu and i could select digital out

My sources are DVDs, and they do have 5.1 and dolby digital.

OK, eject any DVD that's in your computer and launch DVD Player app. Under its Preferences, select the Disc Setup option and choose Optical output. Close the preferences panel.

Turn on your receiver and make sure its input is set to optical (I have to manually set this with my Onkyo receivers). Go to the System Preferences and choose the Sound panel. Does it say optical out? If so, then your Mac is sending an optical signal out the optical port and you should be getting Dolby Digital. Your receiver should switch to the DD emblem.

 

[Leon Kowalski]

1) my toslink cable is only 6ft long, however, I might try your solution if everything else fails (3$ ain't too bad)

Also check that you can see red light at the receiver end of the Toslink cable.
It should be visible whenever "System Preferences > Sound > Output" shows
"Digital Output" -- regardless of whether any sound is playing.

If the light's not visible, it's almost certainly a hardware problem unrelated
to the Toslink cable.

good luck,

LK

 

[freddyaudiophil]

i have a set of Harman/Kardon speakers that plug into the speaker port with a 1/8" microphone jack. The sound comes through loud and clear on these speakers (I've had them for years).

However, I notice that they emit a scratching noise when you touch the plug on the back of the mac. Is this normal? Or should I get a toslink to 1/8 cable instead (as the port on the back of the mac does both)?

Don't get me wrong... 99% of the time it works fine... good bass and treble response. It's only when you accidentally tap the cords or whatever.

freddy

 

[jywv8]

i have a set of Harman/Kardon speakers that plug into the speaker port with a 1/8" microphone jack. The sound comes through loud and clear on these speakers (I've had them for years).

However, I notice that they emit a scratching noise when you touch the plug on the back of the mac. Is this normal? Or should I get a toslink to 1/8 cable instead (as the port on the back of the mac does both)?

Don't get me wrong... 99% of the time it works fine... good bass and treble response. It's only when you accidentally tap the cords or whatever.

freddy

Same thing happens to me with my Creature speakers.

 

[rfanch3r]

i have a set of Harman/Kardon speakers that plug into the speaker port with a 1/8" microphone jack. The sound comes through loud and clear on these speakers (I've had them for years).

However, I notice that they emit a scratching noise when you touch the plug on the back of the mac. Is this normal? Or should I get a toslink to 1/8 cable instead (as the port on the back of the mac does both)?

Don't get me wrong... 99% of the time it works fine... good bass and treble response. It's only when you accidentally tap the cords or whatever.

freddy

Same problem here, I was just about to post the same thing asking for a solution.

 

[ThundaDan]

I did as you said Cave Man and it didn't change anything, there was no sound. Everything was like you said (i set the ouput to optical in my dvd player preferences, and then checked under preference-sound, where it did say digital optical out) but there still was no sound.
Leon : I can see the red light at the receiver's end of the toslink cable.

Any other ideas, or explanation to my problem ?

 

[Cave Man]

Well, that is strange. Your iMac thinks it's sending out optical audio and your receiver decodes DD from your MBP...

Try opening Audio Midi Setup in your Utilities folder and set the DigOut frequency to 48khz as below. Does that change anything?

 

[Leon Kowalski]

Try opening Audio Midi Setup in your Utilities folder and set the DigOut frequency to 48khz as below.

Here's something similar to Cave Man's suggestion, but using the most
universally-supported digital audio format: Pop a commercial audio CD
into the Superdrive and use Audio Midi Setup to set the output format
to 44100.0 Hz, 2-channel, 16-bit. That's the world-standard format for
ordinary audio CDs. Don't waste your time troubleshooting anything
more exotic until you can get that to work. Use iTunes to play the CD.

LK

 

[ThundaDan]

Just tried what both of you suggested, and nothing worked !
By the way, it's great to know there are some people out there willing to give a little of their time to help a fellow mac user. Thanks for trying to solve this issue with me : you guys are trying at least. I called apple care service, explained the problem, and all the guy told me was "ahhh, well, you know, maybe it's just like its kinda not compatible, you know." Yeah right, thanks genius, that was really helpful...
Anyway, if you have any other ideas, just keep them coming. In the meantime, I did order the cable you suggested from monoprice, for 3$ its worth a try.

Dan