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SPDIF Cable Length Critical?

I have decided to buy a Qsonix Music Server and want to place the unit in an adjacent room to my listening room. I will be using the SPDIF digital input to my Resolution Audio Opus 21 CD player for the DAC. The CD player is located next to the preamp and its output is connected using a 1 meter analog interconnect.

This arrangement would require a SPDIF digital cable with a length of about 25 feet to reach the DAC. I realize that it is important to keep analog interconnects and speaker wires reasonably short, but what about a digital connection? Is length critical in that application? Would I sacrifice performance by running a 25 foot long digital interconnect?

I suppose an option would be to buy a separate DAC with multiple types on digital inputs, such as a Benchmark. This would give me more connection and cabling options. Would using a different type of digital cable be better for a 25 foot run?
128x128seasoned
3 responses Add your response
sidssp
1,077 posts
 
For Toslink optical cable, if it is made of quartz glass, you can go as long as
10M (33 feet); if it is made of plastic fiber, you will need a signal booster to
go longer than 5M.

For non-optical connection, I would suggest you use AES/EBU balanced
connection for long run because if its higher signal level (3 to 10V) and
superior noise cancellation ability.
tobias
1,534 posts
 
The only critical point concerning S/PDIF cable length AFAIK is that it should not be shorter than 1.5 meters so that internal reflections are not timed to confuse the DAC's clock. Your longer length should be OK, although Sidssp's point about noise is certainly pertinent.
kijanki's avatar
kijanki
4,428 posts
 
Seasoned - Everything depends on the DAC that you'll use. With jitter rejecting upsampling DAC (like Benchmark) quality of cable is not important at all (as well as transport) and you can use 1000' - doesn't matter. Optical might even help you to break ground loops. On the other hand if you use DAC that doesn't reject jitter then better get good transport and quality digital cable (it is better than toslink). 1.5m is probably optimal to avoid first reflection back on the edge around logic threshold. I'm not sure what is the best solution for going 25' - it sounds a little extreme to me. I would probably choose toslink over digital cable.
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