[ooheadsoo]

True, I just threw in F because it's a very common A/V connection.

 

[Rick]

*BUMP*

Isnt the Yellow Video RCA in composite connectors 75ohms?

 

[FallenAngel]

Quote:

Originally Posted by fsma /img/forum/go_quote.gif *BUMP* Isnt the Yellow Video RCA in composite connectors 75ohms?

Should be, but very likely not. It's not hard to make a 75 ohm cable, get some 75 ohm coax wire and throw on some BNC connectors (better to crimp but if you solder it, it'll minimize the damage). RCA is not 75 ohm by design.

 

[Rick]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif Should be, but very likely not. It's not hard to make a 75 ohm cable, get some 75 ohm coax wire and throw on some BNC connectors (better to crimp but if you solder it, it'll minimize the damage). RCA is not 75 ohm by design.

naturally, however I read somewhere that the yellow video composite ones usually are.

 

[Rick]

and outta curiosity, my onboard ALC885 or something sound card, claims its digital out is SPDIF....but its optical its not coaxial....am I missing something? is there a coax connection somewhere or am I limited to optical?

 

[FallenAngel]

1) Like I said, it should be 75 Ohm, but most cables I've seen were not and RCA cannot be 75 ohms.

2) S/PDIF can be sent via coax cable or optical.

 

[FallenAngel]

Quote:

Originally Posted by syllabus /img/forum/go_quote.gif My coaxial cable made of pure silver and not even 75 ohm in impedance, terminated with RCAs on both ends and connected to my CDP through a RCA->BNC adapter, has a superior sound to a Blue Jeans Belden 1694A terminated with BNC to RCA (so without any adapter on the CD player side). Superior as in more detailed, with stronger and more firm bass.

Whatever you say, if you think so, but I'd place a wager that you're losing some detail over a proper coax cable, even a cheap one from BlueJeansCable (which has nice cables by the way).

 

[rds]

Remember that the 75 ohm standard was developed for analog video signal where impedance matching is crucial. For digital audio the argument becomes much more tenuous. Ideally you want the maximum power transfer by impedance matching, but if your cable is 68ohm or 81 ohm I really doubt it'll make any difference at all.
It makes sense to use 75 ohm cable. All you have to do is get a regular old school tv cable and put some rcas on it. In my opinion that is more than adequate for spdif. But then again I've just be learning about this recently.
In regards to a digital cable having better bass, I'd like to hear what mechanism could be at work there.

 

[FallenAngel]

Quote:

Originally Posted by syllabus /img/forum/go_quote.gif LOL, I thought I said that the non-75ohm silver coaxial has more detail and more bass than the Blue Jeans BNC->RCA made with Belden 1694A. My idea is: silver is a superior conductor for digital signals, at least to the copper that is in the Belden cable.

Nope, the non-75Ohm will likely have less detail (the most noticeable effect of jitter).

How is silver a "superior conductor for digital signals"? Considering the length of cable and the extremely tight signal timing requirements of the S/PDIF standard, I don't see this to be true at all. The main reason you want a cable that is perfectly 75 ohm throughout, terminated in 75 ohm connectors and also around 15 feet in length is because the S/PDIF signal is sent at exact intervals and the clock is reconstructed from the signal at the receiver. Copper/Silver or most other metals for that matter shouldn't matter much as long as it meets the signal requirements for passing the digital signal and having as close to zero timing difference between conductors and conversions (which is why coax will always beat optical because the conversion to/from optical will never be as perfectly timed), then the cable should work perfectly.

With digital cables the important thing is perfect timing, impedance matching, master clock, conversions, they all play a part.

 

[rds]

It seems that almost any quality modern DAC will re-clock the signal. Afaik, the data is stored in a buffer which is fed out by the DAC's own clock. Do I have that right?

 

[FallenAngel]

Quote:

Originally Posted by rds /img/forum/go_quote.gif It seems that almost any quality modern DAC will re-clock the signal. Afaik, the data is stored in a buffer which is fed out by the DAC's own clock. Do I have that right?

I don't think most DACs reclock and the "buffer" that some use is embarrassingly small to the point of practically useless in terms of behaving as an actual "buffer" Otherwise, you'd get a delay in your music from the source and that's not very likely.

Remember, S/PDIF is an ongoing signal, as it gets to the DAC, it gets converted and that's it.

 

[LostOne.TR]

I can see how his comments might seem kind of strong, but he did say Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif Nope, the non-75Ohm will likely have less detail (the most noticeable effect of jitter).

I don't remember exact # for the recommended length, but everything he's said is pretty much true-- in regards to there being an optimal length, for the reasons he stated, and the BNC connections being the best method. True 75 ohms there, even though many places advertise "true 75 ohm RCA connector" or whatever, in most cases it still isn't.

looking at the BJC page... they say the "Belden 1694A" is a true 75ohm coax cable (cable itself).
The "Canare RCAP" (rca plugs) are described as "designed for the best possible impedance match with 75 ohm video coax." The only time BJC actually implies it to be a true 75ohm cable throughout is with the BNC connectors "Canare BNC plugs--true 75 ohm plugs ..."

FA has only stated reasons for why he would likely believe the silver cable to have less detail, and why he thinks the silver vs copper comparison doesn't have as much sway here. He's not actually at any point flat out denied your findings, just has written why he would disagree with them.

Interesting though that neither of the cables used are true 75ohm in this case. RCA -> RCAtoBNC, then a RCA->BNC cable. Maybe the closer match of the rca to rca offers a more optimal path than the RCA->BNC?

 

[rds]

I think onboard reclocking is the most sensible solution.
The Sabre 8 has that built in and it's a feature that can be easily added (during design) to DAC chips that don't have it integrated. For example, the Opus and Metronome combination.
After all the reason to use digital is to overcome the lossy problems associated with analog. If you have to treat your digital interconnects as if they were analog then I think something has gone wrong. Of course there is a point where an interconnect is so poor that 1s could become 0s, but I think that's pretty extreme.

Quote:

The fact that I found a non-75 ohm silver coaxial to sound better than a 75 ohm Belden coaxial, instead, is tangible fact.

Yeah, but I think the argument is that your findings might just be in your mind. God knows I've never tried to hear differences between wires. I doubt that I could.

 

[LostOne.TR]

Quote:

Originally Posted by syllabus /img/forum/go_quote.gif Never said "hidden", just abstract, theoretical. The fact that I found a non-75 ohm silver coaxial to sound better than a 75 ohm Belden coaxial, instead, is tangible fact.

Yeh sorry about that. I mistyped, and had been editing my post while you relied to it.

 

[FallenAngel]

Yep, applied theory. I have used some crappy non-75 ohm cables and they sounded quite muddy compared to the Belden 1694A. I can't tell the difference between Mogami coax and the Belden coax.

I don't deny that you like your silver cable more, I just don't believe it sounds as "accurate". Of course if you want to send it over, I'd gladly audition it and get back to you with what I think.