5 Replies Latest reply: Aug 19, 2010 8:08 PM by DilJaey
robpmit Level 1 Level 1 (0 points)
I am trying to figure out the best way to connect my iMac to a stereo receiver. Which option will result in superior sound on my home stereo: (1) running a TOSLINK cable from the iMac's optical digital audio out port to the receiver's optical input or (2) connecting the iMac to the receiver using a USB DAC?

Thanks for your help.

iMac 21.5-inch 3.06 GHz Intel Core 2 Duo, Mac OS X (10.6.3)
  • R C-R Level 6 Level 6 (16,515 points)
    That will depend greatly on the relative quality of the DAC & associated circuitry in whatever USB audio interface you might use vs. the quality of what is in the receiver.

    In general, a high end external audio interface, especially one aimed at the audiophile or professional markets, will outperform the converter in a typical receiver, but beyond that any more specific advice is impossible without knowing more about your home stereo & which USB devices you are considering using.
  • robpmit Level 1 Level 1 (0 points)
    Thank you. Someone told me that if I were to go with option 1 (TOSLINK), I would be using the headphone amp (not good) to send the single to my stereo. In other words, I would essentially be listening to headphones on my speakers (electronically speaking). Do you agree?
  • R C-R Level 6 Level 6 (16,515 points)
    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.
  • robpmit Level 1 Level 1 (0 points)
    Thanks again. Your response was very helpful.
  • DilJaey Level 1 Level 1 (0 points)
    I am currently sending an analog signal from My (Late 2006 model) iMac to a Pinoeer receiver. Headphone jack to RCA (LR). The sound out of the receiver switches to a single speaker after a few minutes and then just flickers back to two speakers intermittently. Any other device connected to that receiver (even via the same headphone jack) does not seem to have that issue. Should I be using a specific cable or invest in a new receiver?