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How can different CAT5/6 cables affect sound.

While is is beyond doubt that analog cables affect sound quality and SPDIF, TOSlink and AES/EBU can effect SQ, depending on the buffering and clocking of the DAC, I am at a loss to find an explanation for how different CAT5 cables can affect the sound.

The signals over cat5 are transmitted using the TCP protocol.  This protocol is error correcting, each packet contains a header with a checksum.  If the receiver gets the same checksum then it acknowledges the packet.  If no acknowledgement is received in the timeout interval the sender resends the packet.  Packets may be received out of order and the receiver must correctly sequence the packets.

Thus, unless the cable is hopeless (in which case nothing works) the receiver has an exact copy of the data sent from the sender, AND there is NO timing information associated with TCP. The receiver must then be dependent on its internal clock for timing. 

That is different with SPDIF, clocking data is included in the stream, that is why sources (e.g. high end Aurenders) have very accurate and low jitter OCXO clocks and can sound better then USB connections into DACs with less precise clocks.

Am I missing something as many people hear differences with different patch cords?

retiredaudioguy
retiredaudioguy OP
287 posts
 

I have been setting up my new T8 streamer.  I was playing a work streamed from Presto and needed to re-route the Cat-5 cable.  When I unplugged the cable from the T8 - nothing happened; the music continued to play for about 30 seconds.

Since the link between the switch and the streamer uses TCP/IP and so is error free, given a competently designed streamer, and the timing is generated by the streamer's clock, this suggests that an SQ changes with cable changes are not data related but are caused by, loosely speaking, noise, picked up by the cable.

This suggests an experiment for those who hear hear SQ differences.  Connect the streamer using the WORST cable that you have.  Start playing, noting the SQ deficit vs your best - and unplug the cable.  Do the problems go away?  

Since the issue is posited as isolation - using optical connections e.g. - no cable should be the ultimate isolation. 

 

audphile1's avatar
audphile1
7,882 posts
 

The data is buffered so unplugging the cable won’t affect what’s already been allocated to buffer. That 30 secs of music is in your streamer’s buffer. 
Aurender has an even better design with a very large SSD cache. When I had my N200 I unplugged the network cable and it went thru my entire playlist without stopping. I couldn’t control it from the app obviously because it wasn’t connected to the network but it will play until it runs out of cached music. 

westcoastaudiophile
819 posts
 

@audphile1 +1 "The data is buffered so unplugging the cable won’t affect what’s already been allocated to buffer"

it’s correct statement! there is a FIFO register (first in first out) employed in interface receiver, which does decouple any missing/corrupt/resent bits effect to actual transferred data, unless FIFO register is shorter than number of errors in the stream. properly designed interface will eliminate any sound effects, even if you receive data stream from Mars, sound quality will be the same! 

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