SPDIF Audio Cable

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Running a length (20') of RG-6/U cable from PC to receiver. Added RCA adapters to both ends. Most "experts" say that RCA ends are not 75 ohm compliant. Why does everything use them then. What effects am I going to experience with my setup. Should I mod receiver input and motherboard output to something else (BNC).
 
I wouldn't worry about it. The impedance mismatch is too small, at the frequencies we are working at, to be of significance. Besides, there's also some impedance mismatches in the boxes' internal wiring around the receive and transmit SPDIF circuits. And as SPDIF is a 75 ohm impedance system, any decent video cable will work fine.

Anyway, with digital signals, if it works reasonably well it works quite well. Another way to say this is that a bad cable will fail quite obviously.
 
trunkmonkey said:
Running a length (20') of RG-6/U cable from PC to receiver. Added RCA adapters to both ends. Most "experts" say that RCA ends are not 75 ohm compliant. Why does everything use them then. What effects am I going to experience with my setup. Should I mod receiver input and motherboard output to something else (BNC).

The difference will be similar to comparing original CD to its CDR copy: you may notice it, but not neccessarily.
 
You could extend that to any cable that makes your D/A box sound different indictes it needs fixin'. Or at least some serious tweaking.

When you get all the reflections down to almost zilch (and that means on both ends), you should not be able to detect a difference.

As for "sophisticated reclocking", I assume you are refering to an ASRC or a secondary PLL.

The less reflections, the less hard the PLL will have to work. (Mind you, an ASRC acts as a digitally implemented secondary PLL. Some like them, some hate them. Another story for another time.)

So, let us take the secondary PLL for the sake of discussion. Hard for an average DIYer to design. Easy to buy and install if you get one from one of our resisdent clockmongers. They just cost $$$$$$$$.

Compare the cost of it to BNCs, a linear input stage, and a decent driver. Not hard to design or build. And much less expensive. You are going to have to build those anyway, regardless if they are done properly or not.

Yep, some added expense if you mod your gear. This is DIY........kvetching about minor added costs is verbotten.

OK, but back to your question:

Yes, when you implement one of those, and one could make a strong case for doing so, the differences are hard to pick out.

In either case, there is little excuse for not doing it the right way. Phred will insist he can make an RCA connector scheme that compensates for those anomalies, but that is Phred. Without a TDR, your chances of doing so are damn near zero.

Again, I have written about this more times than I can remember. Not only here, but on 2 other forums. The search engine is your friend...........

Jocko
 
Jocko
What would you suggest be built as per original post. I imagine there are a lot of people now storing AV on their PC and connecting to amps/receivers. PC's are probably nowhere close to the audio gear.

Again, I have written about this more times than I can remember. Not only here, but on 2 other forums. The search engine is your friend...........

I have done a lot of searches - just looking for a plain jane answer

Also searched and found this Canare plug
 

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Its unlikely the RCA socket or the PCB tracks are 75ohm.

The likes of the canare 75ohm RCA are just there to give people the warm fuzzy feeling that everything is perfect and to add cost to premade cables. (me? cynical? never!)

You will never see an RCA used for video or digital signals on pro or broadcast equipment, its pretty much all BNC. Certainly we use RCAs for audio and nothing else.
 
Thank you Jocko
I probably will experiment much in next half year with transmission media, both electical and optical, some with high signal-induced-jitter.
I plan to use a cascade of PLLs and a FIFO in style of SDH/SONET systems reclockers to destroy the jitter.
My question is what PLL would you suggest? and what loop filter frequencies in cascade of two or three PLLs.
I guess 74HC40(something..?) isn't a best choice here.

best regards
Adam
 
Sorry. Can't help myself.

"Transparent Reference 75 Ohm Digital Link

The large, polished OFHC center conductor is surrounded by proprietary air/spiral teflon insulation to reduce noise and increase propagation speed. Superior shielding results in a cable that is free from interference. This hefty cable may be precision terminated with custom designed coaxial RCAs or instrument grade BNCs."

:rolleyes:
 
phn said:
Sorry. Can't help myself.

"Transparent Reference 75 Ohm Digital Link

The large, polished OFHC center conductor is surrounded by proprietary air/spiral teflon insulation to reduce noise and increase propagation speed. Superior shielding results in a cable that is free from interference. This hefty cable may be precision terminated with custom designed coaxial RCAs or instrument grade BNCs."

:rolleyes:

Spot on!
 
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