[Audio Jester]

I have been looking into spdif connections and noticed that most of the low-mid fi products that I have seen prefer RCA ports instead of BNC. It appears that on paper the BNC is superior, so why is it not the standard for spdif ports?

Edit: Actually, a lot the high-end stuff I have seen also does not have BNC. What gives?

 

[leeperry]

it's like I2S...it's starting to show up slowly.

manufacturers go for a quick buck, and except for audio nerds that praise the j..... gods, noone gives a damn about BNC for audio...why not DIN5? who needs RCA after all

 

[Audio Jester]

so, do you agree Leeperry that BNC is better than RCA or do you feel that it is overrated?

 

[leeperry]

I haven't compared both(and neither in many units, because an isolated test wouldn't have much meaning), and before someone shows some clear measurements differences...the doubt will still be there.

75Ω very much matter for video, because 50Ω is said to introduce ghosting...does it also matter for S/PDIF? I'd guess it does? do 75Ω RCA connectors exist at all? will your coax interface and DAC both work in plain vanilla 75Ω from start to end too? you're only as strong as your weakest link, as usual.

I personally think that there's far more things to worry about than 75Ω BNC connectors...but that's just me! some ppl w/ (self-proclaimed) platinum ears say that they can hear 1ps jitter, 75Ω BNC prolly means the world to them

 

[Audio Jester]

LOL.
I think that my current level of tinnitus has negated my "platinum" ears.
Thanks for your answers Leeperry.

 

[Currawong]

The discussion came up likely because when someone asked why Audio-gd DACs don't have AES connections, Kingwa said he measured the lowest jitter on BNC and RCA connections and the higher on optical and AES. To prevent signal reflections in as S/PDIF digital cable, ideally it should be 75 Ohms throughout. RCA plugs and sockets are technically incapable of this, though a couple of designs exist that overcome this limitation. I think the high-end audio market just switched to using RCAs for S/PDIF for the most part because it was easier to sell crazy cables without having to have different versions for digital. Anyway, that is, as far as I can see, where all this deal about BNC vs. RCA came up.

 

[Audio Jester]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif as far as I can see, where all this deal about BNC vs. RCA came up.

Actually Currawong, I was asking because Slim.a got BNC put on his DAC19 and he felt it was a superior input to the standard RCA (for spdif). I am about to get a DAC19 so I thought I might check it out, get some different perspectives... so this thread was born.

 

[Shark_Jump]

I asked about BNC contacts a while back as they have been used on scientific equipment, oscillascopes and the like, for years.

The answer I got was they are a more robust contact than an RCA and are easier to take on and off.
Considering just this they would be of marginal use on a Hi Fi system unless you kept fiddling around with the cables.

No-body mentioned BNC are a better contact in terms of SQ than an RCA. Would be interested to know if anyone has done studies into this.

Just off the top of my head I would have thought the contact quality would be determined by:
actual contact area
abscence of small gaps (to avoid sparking)

 

[stef50millbay]

RCA cables were engineerd for analog signal  while BNC was engineered for digital signal.

 

[JerryLove]

Since someone else resurrected it.
Quote:

I have been looking into spdif connections and noticed that most of the low-mid fi products that I have seen prefer RCA ports instead of BNC. It appears that on paper the BNC is superior, so why is it not the standard for spdif ports?

Convention. RCA became the standard long ago. Would you go buy a CD player with BNC connectors knowing that there was no AVR or DAC it would connect to? Neither would anyone else. Plus "when". Once you get into the 90s, you get optical which is superior to either: and now HDMI.
 
It may also be worth noting that BNC connectors are physically larger (the standard cables are also stiffer and with more problems related to kinking). If we were going to move to a different analog connector: why not XLR which is better still?
 
The fact is that RCA works and works well. There's far more bandwidth than the audio needs, and they can be made at reasonably long runs. The analog step-up is XLR, and after that we really should be speaking digital.

 

[Currawong]

I think you're confusing digital connections with analogue connections.  The reason BNC is superior for S/PDIF digital connections is that, if the correct plugs and cabling is used, is that it has the correct 75 Ohm characteristic impedance. If any part of the digital connection isn't 75 Ohm, then you get signal reflections which can interfere with the digital to analogue conversion and cause audible distortion.

 

[endless402]

you'll see BNC, AES, I2S on higher end stuff  (eg Bryston, PS Audio, Wyred 4 Sound, Berkley)
 
RCA on lower end stuff
 
 
As currawong said, bnc has the correct 75ohm. That's why you'll see stereovox and other cable manufacturers have bnc cables iwth rca adapters

 

[JerryLove]

Quote:

I think you're confusing digital connections with analogue connections.  The reason BNC is superior for S/PDIF digital connections is that, if the correct plugs and cabling is used, is that it has the correct 75 Ohm characteristic impedance. If any part of the digital connection isn't 75 Ohm, then you get signal reflections which can interfere with the digital to analogue conversion and cause audible distortion.

 
True catch... and BNC is certainly in use in digital (T1 lines for example).
 
The use of RCA for digital connection would, I'd bet, still go back to the presence of so much RCA hardware. Manufacturers were already building equipment with RCA connectors, and RCA cables were common and, obviously, do function.

 

[Furface]

BNC connections have both 50 & 75 ohms impedance. Why BNC less common is apparently on general consumer market devices. Whereas in pro-console/broadcast console level, most of their equipments have BNC connections. Reason for the locking as versus RCA. BNC connections also found in inductrial machines, scientific equipments as well, CCTV cameras, etc.

 

[JerryLove]

I'm still trying to figure out why BNC-style connectors were not used in cable television.