Changed bass response swapping from 'audio' to 'coax' interconnect

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d0dja

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So this has me a bit mystified. Being a bit new at this I'd hooked up my CD/DVD player to my AV receiver with reg'lar moderate quality audio interconnects powering crap old speakers. I then connected the coax S/PDIF out to the AV receiver, and got a marginally better result. So far, so good.

I got better speakers as part of a DIY building job (sigh, crossover design still in progress) and decided to get a better interconnect, went to the shops, did some reading, and discovered that I was being a doos - that standard audio cables are basically twisted pair, sometimes sort-of-shielded, but not made to any spec, whereas a coax interconnect MUST be 75ohm shielded, etc. Swapped the cable over and was boggled how much better it was - not high end, the bass response. Huge change below 100Hz (roughly).

Swapped back to the audio line interconnects, and was still dramatically better than using an audio cable for the S/PDIF connection.

Swapping back and forth between coax and line, and coax was clearly better (although not radically... the improvement starts to move from blindingly obvious to subtle).

Right. So now to the question ... why would a coax cable give a MUCH better low-freq response than a regular audio cable plugged into the S/PDIF socket?

From what I understand, S/PDIF is an uncorrected data flow of (effectively) packetised audio samples with some bits to indicate channel, etc, running at about 1.5MHz, data rate of 2.6Mbps (line rate of 5.8 'cause its Manchester).

So if I have a crappy cable that can't provide enough bandwidth, or lots of reflections, I would get a problem either with clock recovery, or bit corruption, which would either result in the receiving end not being able to decode (ie not work at all) or get noise/pops, etc. Or increased jitter artefacts, maybe (although I really doubt if these would be hearable). 

Why would it give me less low-end fidelity?  ???










 
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