HDMI vs. toslink audio quality question

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Level 1

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HDMI vs. toslink audio quality question

I'm trying to figure out the best way to play/preserve my lossless music stored on my iTunes. Unfortunately, I have three devices with a toslink (digital optical) output (apple TV, blu-ray, HDTV), and only one toslink input on my stereo. However, I do have both the apple TV and blu-ray connected to the tv via HDMI, and the TV has the toslink output.

Is there an audio quality loss, degradation or difference if I play my music through the iMac>airplay>ATV>HDMI>TV>toslink>stereo, or do I really need to play my music through the iMac>airplay>ATV>toslink>stereo and bypass the TV?

Better yet, is there a difference in the audio signal processed by the ATV's HDMI, or is it identical to the signal coming from the toslink?

Message was edited by: mightyprops

Mac OS X (10.5.8)

Posted on Jan 10, 2011 2:46 PM

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Answer 1

sinfonye

Level 1

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Apr 5, 2011 2:45 AM in response to mightyprops

You may be asking this question in the wrong place. You may get a better answer
at AV forum ( http://www.avforums.com) or AVS forum ( http://www.avsforum.com).

To answer your question as best I can. Including the TV in a TOSLink setup will add an extra decode/encode
stage. This will affect the timing of the audio signal, perhaps degrading the quality of
the signal (there is no timing synchronisation over TOSLink, though receivers/DACs
can compensate). For similar reasons, keep your runs of optical fiber short: 1-2m if possible,
6m as an absolute theoretical maximum.

TOSLink has much higher audio bandwidth than HDMI: 125Mb/s versus 36.86Mb/s. This may
be more significant for multi-channel audio, though, since even 320Kbps should cover your needs.
TOSLink is also completely immune to electrical interference, so you don't need to worry about where
you run the cables.

HDMI will synchronise audio to video, which is better if you're watching movies/TV,
but the audio is not clocked (so you can get "jitter" here too).
Again, keep to short cable runs to avoid video/audio distortion, and minimise the number of
devices in the chain for the best audio experience.

So it's not clear cut. For audio, your best solution is probably TOSLink direct to the DAC/stereo amp, but the other
routes may be completely acceptable (you need to listen to them to see whether you can hear any
effects). For video+audio, use HDMI.

If you want really good sound quality (and can afford it), add a separate DAC. I have my AppleTV 1G
connected through a Cambridge Audio DACMagic to my old stereo amp, and it's great, but this
is audiophile territory! Most people will be happy with a simple TOSLink to amp connection.

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Answer 2

JKStraw

Level 1

0 points

Jun 19, 2011 2:00 PM in response to sinfonye

What software are you using to connect to your ATV? Are you only streaming Apple lossless? I wish I were able to stream FLAC files but in any terms streaming downgrades all files to 44.1 kHz and 16 bit depth are they not?

The sample rates for optical are max 48kHz where if you can run coaxial you can achieve 192 kHz 24bit. So, if you can run HDMI video and coax for audio you will be far better off.

I currently run for audio: either macbook pro USB to Benchmark DAC1 HDR out via balanced to either Rotel or parasound JC2 Preamp or stream to AE then out optical. I dont seem to hear too much difference except for high end recording and then wow the FLAC files and DAC really deepen the bass and have very tight control on the mids.

If you want true Audiophile, download FLAC only or rip your cd's to FLAC and run them to your DAC and see how it compares.

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Answer 3

JKStraw

Level 1

0 points

Jun 19, 2011 2:05 PM in response to mightyprops

You best bet is running coax to your DAC for all audio. Try running coax from your blu-ray if possible or coax off the tv to your DAC and see if you hear any difference.

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