Connecting Imac to Cambridge Audio Azur

Question

Hi everybody, this may be a little off topic, but i´ve found people here to be the most knowledgeable.
I´m planning on getting The CA Azur 540R Receiver. From what i´ve read my Imac has a "Headphone/optical digital audio output (minijack)". Is there a cable for connecting directly my Imac to the optical audio input on the receiver? what type of cable should i get? Will i be able to get true 5.1 DD sound from say: a dvd movie playing through the dvd player on the Imac?? Thanks everybody for your time.
Imac Core 2 duo 20" 1GB Ram   Mac OS X (10.4.9)  

Answer 1

I do not agree. The headphone amp outputs a conventional two channel analog signal on the multi-purpose 3.5 mm audio output jack on all Intel iMacs. But that same jack outputs a digital optical signal if the iMac senses a mini-Toslink adaptor plug has been inserted instead of an analog stereo TRS (tip ring sleeve) plug.
IOW, the same jack furnishes two entirely different kinds of output (analog or digital) depending on what is plugged into it. The digital output encodes the audio (which could consist of multiple channels of audio) on a single beam of digitally modulated light. The analog output is two separate signals, each on its own electrical conductor, derived from the internal DAC in the iMac & amplified by the amp to provide enough power to drive headphones.
It is possible that the amp does double duty to also drive the light source for the digital output, but that is in no way is comparable to using it to drive headphones -- for the digital output all it would have to do is switch the light level between the digital high & low states.
My guess is that whoever told you about the headphone amp either did not know about the dual function of the jack or thought you were talking about an analog connection to your stereo.