Basic question: I have both SPDIF and Optical output from my CD player to be the input to my DAC. I probably can't hear any difference between them. But assuming I can't hear a hum (ground loop), is one likely to be better than the other?
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Tell me again: Should I use the Optical or SPDIF interconnect?
- Thread starter MediumRare
- Start date
Optical is spdif... Should be the same...
Optical or coax are the two different digital output connector types. Both use S/PDIF as the content transfer format to send up to 5.1 multi-channel audio. Whether one can hear a difference between them is debatable. Coax cables are subject to interference if not well constructed and plugs subject to corrosion but can run longer distances than optical without active repeaters. Optical are less susceptible to corrosion and interference with people claiming less signal loss over distance with glass fibers instead of plastic. But these are all in that nitpicking golden ears range. Good cables of either in the short runs of an audio stack should do fine.
restorer-john
Grand Contributor
Use optical. It's way cooler to have your audio transferred between one box and another using pulses of light. 
somebodyelse
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Emphasis on 'should' - sometimes a design screwup means one will perform better than the other, but it would need testing to find out.
OP
- Thread Starter
- #7
Let me rephrase: Optical or RCA?
Last edited:
restorer-john
Grand Contributor
OP
- Thread Starter
- #9
No, you need an RCA on each end for it to work...
Tom C
Major Contributor
I thought some devices limit the bandwidth on optical vs digital coax. For example, during playback of a Blu-ray disk with a lossless audio format, 192/24 audio is only available from the hdmi connection. Digital coax is less than that, and on some systems optical is less than digital coax.
OP
- Thread Starter
- #12
The DAC sits on top of the CD player and yes.
Use copper coax if you don't want to be waiting around all day for the light to propagate through the fiber and the music to start.
Electrical signal via copper - about 300,000,000 m/s.
Light via fiber - about 204,190,477 m/s.
Electrical signal via copper - about 300,000,000 m/s.
Light via fiber - about 204,190,477 m/s.
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solderdude
Grand Contributor
RCA allows for higher bitrates. Optical (the plastic light-sewer TOSLINK crap) is limited to 96/24 but sometimes still works with 192/24.
Real fiber optics (MM and SM) are not limited but there won't be many (if any) modern DACs have that.
Also one should take into account the implementation in the DAC itself and how jitter reduction is handled.
So... when you have > 192/24 RCA, below that what's most convenient and works well with the gear in question.
To avoid or break groundloops from PC's Optical is the way to go.
Real fiber optics (MM and SM) are not limited but there won't be many (if any) modern DACs have that.
Also one should take into account the implementation in the DAC itself and how jitter reduction is handled.
So... when you have > 192/24 RCA, below that what's most convenient and works well with the gear in question.
To avoid or break groundloops from PC's Optical is the way to go.
Last edited:
Eirikur
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BluRay restricts the quality artificially - they can "control" the use of the digital content over HDMI using HDCP, but not over coax/optical S/PDIF.
This means that only HDMI will give you the full hires content, while both S/PDIF connections will be sampled down to max. 48kHz/16.
S/PDIF can carry a copy-protection bit, but this is easily defeated by simply not looking at it or filtering it out of the bit stream.
solderdude
Grand Contributor
I know, was just throwing in some background info on when to choose which method.
In his case: what's most convenient and works well with the gear in question.
In his case: what's most convenient and works well with the gear in question.
Electrical signal propagation velocity in typical cables is about 200e6 m/s, roughly the same as your figure for light in plastic fibre. That should be no surprise since electrical signals are actually electromagnetic waves (light) travelling in the cable dielectric (plastic).
Well, I figured I had plagiarized a bad reference (how else would I know), but the first link checked today:
https://www.everythingrf.com/community/what-is-propagation-velocity-in-a-cable
(assuming they plagiarized good data)
Via copper - 65.9% up to 90% SOL - 197,568,200 to 269,820,000 m/s
Thank you for pointing out my factual error.
https://www.everythingrf.com/community/what-is-propagation-velocity-in-a-cable
(assuming they plagiarized good data)
Via copper - 65.9% up to 90% SOL - 197,568,200 to 269,820,000 m/s
Thank you for pointing out my factual error.
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