# Digital Optical Audio input

**URL:** <https://boards.straightdope.com/t/digital-optical-audio-input/570353>\
**Category:** Factual Questions\
**Created:** [February 6, 2011, 2:32am UTC](https://boards.straightdope.com/t/digital-optical-audio-input/570353 "2011-02-06T02:32:21Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\
**Post date:** [February 6, 2011, 2:32am UTC](https://boards.straightdope.com/t/digital-optical-audio-input/570353/1 "2011-02-06T02:32:21Z")

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I have several devices that can accept digital optical audio input. The hookup instructions usually show that the optical cable it to be hooked up in parallel to the HDMI connection. Sometimes I hook up the optical cable in parallel to the HDMI and sometimes don’t. I can’t tell the difference with or without, and my Onkyo Dolby 7.1 receiver can’t seem to either. Is the optical cable supposed to be carrying something that the HDMI cable isn’t? What am I missing?

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**Author:** ![Anthony\_N](https://avatars.discourse-cdn.com/v4/letter/a/858c86/32.png) [@Anthony\_N](https://boards.straightdope.com/u/Anthony_N)\
**Post date:** [February 6, 2011, 2:43am UTC](https://boards.straightdope.com/t/digital-optical-audio-input/570353/2 "2011-02-06T02:43:22Z")

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HDMI carries the digital audio signal. Some equipment cannot receive the 5.1 audio over HDMI so in those cases the optical link would be superior. If your receiver seems to be seeing the full surround sound audio signal, you can use either method.