Want to highlight a helpful answer? Upvote!

Did someone help you, or did an answer or User Tip resolve your issue? Upvote by selecting the upvote arrow. Your feedback helps others! Learn more about when to upvote >

Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

Optical audio output for IMAC

My new IMAC 2.66gh 24" is coming. Just wondering if the IMAC can output true bit stream audio signal through the toslink cable. I have a Logitec 5400 THX 5.1 Speaker system support THX, Dolby Digital, DTS hard decode. What I heard from other website saying is IMAC can only output 2.1 channel audio sound through optical. If that is true then my 5.1 speaker system is useless.

IMAC, Mac OS X (10.5.7)

Posted on Jun 17, 2009 6:57 PM

Reply
4 replies

Jun 17, 2009 10:18 PM in response to rkaufmann87

Certainly it will output any compressed 5.1 audio through the TOSlink. Perhap I should clarify my question, will the IMAC output "Bit Stream" (uncompress audio signal) to my speaker and decoded it through the hardware decoder in the speaker amplify? In other word my speaker would display DTS decoding when I play a DVD movie that has DST sound. Sorry for the confusion.

Jun 17, 2009 10:48 PM in response to kl2999

Hi Kl2999

Welcome to Apple Discussions

Have a look at the > [iMac Audio System Audio Developer Notes|http://developer.apple.com/documentation/Hardware/Conceptual/HWTech Audio/Articles/Audio_implementation.html#//apple_ref/doc/uid/TP40003978-SW281200331167]

+*S/PDIF Optical Digital Output*+
+The S/PDIF optical digital output is automatically selected when an S/PDIF optical digital output device is detected on the external combo audio port. The S/PDIF optical digital output supports PCM and AC-3 audio formats with the following stereo data stream characteristics:+

+PCM: 16, 20, or 24 bits per sample at sample rates of 44.1 kHz, 48 kHz, or 96 kHz+
+AC-3: 16 bits per sample at sample rates of 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, or 192 kHz+
+The S/PDIF optical output channel status conforms to IEC 60958-3 consumer mode digital audio.+

+During playback of a 1 kHz sine wave (S/PDIF output format at 0 dBFS output level, 44.1 kHz sample rate, 24-bit sample depth, unless otherwise specified) the digital audio output has the following nominal specifications:+

+Jack type: 3.5 mm (1/8”) stereo combo+
+Digital audio signal-to-noise ratio (SNR): > 130 dB+
+Digital audio total harmonic distortion + noise (THD+N): < -130 dB (0.00003%)+

Dennis

Jun 17, 2009 11:08 PM in response to kl2999

The specifications don't mention DTS, I am familiar with that format however it doesn't look like it is supported on the iMac. Please read over the specifications as Dennis noted. Most recording that have DTS also have DD 5.1 so if you are playing something recorded in DTS chances are excellent it will also have a DD 5.1 soundtrack as well.

Regards,

Roger

Optical audio output for IMAC

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple ID.