Why so few BNC's used on digital gear?

[kchap]

Doesn't the center pin on the 50 ohm version have a diameter that is different from that of the 75 ohm one such that plugging the thicker pinned one into the thinner pinned receptacle can permanently deform the receptacle?

Most definitely. It caused a lot grief in my younger days. Once you push a 50Ω connector into a 75Ω female socket you spread the metal leaves so it no longer works properly with 75Ω connectors.

 

[sergeauckland]

Most definitely. It caused a lot grief in my younger days. Once you push a 50Ω connector into a 75Ω female socket you spread the metal leaves so it no longer works properly with 75Ω connectors.

When I worked for a broadcast TV equipment manufacturer, bringing a 50 ohm BNC onto the premises was grounds for dismissal. Did horrible things to the return loss when trying to calibrate a vision mixer or PAL encoder.

S.

 

[DonH56]

There you have your answer! Average home equipment are not as heavy as lab equipment and perhaps it will be difficult to perform this operation without holding the device with your other hand. I don't see the average person connecting the RCA on the back of the TV pushing an turning... wait a second, that's another thing, RCA plugs can be very close together. I guess this is another important factor in consumer electronics.

Maybe... I have seen and owned plenty of gear that required a hand to hold it in place to push on (or remove) an RCA, even with "normal" RCAs and not these new versions that need vise grips to get on and off.

That must be because I've never been in a lab outside academic circles: college, some research institutes, etc.

Students are not always the best caretakers of lab gear IME... But wires everywhere to supplies, test gear, and the device under test (DUT) inevitably causes some mistakes, whether fresh out of college or 40+ years later (don't ask how I know this).

 

[Gibsonian]

Wish they were all BNC. But they are not and not going this way. In the end don't know if I could ever hear or detect a difference in analog or digital connections comparing the two.

 

[earlevel]

It's an ongoing amazement to me how many manufacturers use RCA's for their SPDIF interfaces. The inadequacies of RCA's has been repeatedly demonstrated even if 75 ohm cable is used. Is this really to just save a couple bucks? Lower end McIntosh stuff has RCA's as does most Japanese gear regardless of price. It's not like BNC's are really so exotic, and 75 ohm cables are readily available. In fact, the general lack of inputs is an annoyance. AES/SBU seems to have become and exotic feature. And not everybody wants to use USB or Toslink. Rant over. Thanks for reading.

I get that this is a rant—and a good one. I'm just commenting to the board, you probably realize this...

To the first sentence, it's basically self-fulfilling. S/PDIF is basically AES3 made so cheap that manufacturers could include it, even when most buyers were unlikely to use it, with almost no impact on cost. If this were not the case, S/PDIF would have never gained significant manufacturing support. (I have at least three devices around me that support it, I've never used it in my life.)

Not only are RCA jacks literally stamped out of thin metal, they don't take up much panel space or depth. They work out well to gang a bunch on a molded plastic base that takes just a few screws to secure to back panel, which is already being done to support 20+ analog ins and outs for a receiver or preamp. And, significantly, the manufacturer can throw in a molded cable with plugs—no moving parts—at slight cost.

BNC is not expensive, per se, but it's a step up from almost nothing—impact to the panel, more expensive connectors and cables with tighter tolerances. So, it a nice upgrade, but when everything else has RCA, that upgrade would need to be RCA + BNC...yet TOSLINK has more utility with its noise/hum immunity, so a BNC-supporting manufacturer needs all three, or disappoint more consumers than they will please.

RCA is wretched, but at the cheapest it still works—for consumer gear that is rarely reconfigured—and allows lots of ins and outs at minimal cost.

Pro audio is a different story, but even then BNC for me is limited to digital clocks and MADI support. But my converters only have ADAT and MADI optical, so it's MADI optical. But that does highlight the, er, "beauty" of S/PDIF—at one extreme you have digital interfaces that are expensive enough that they are often implemented as an extra cost module (MADI, Dante...), despite the added cost of modularity, while S/PDIF is just there if you need it, because it's so cheap. Firewire failed at a time when it was the only good choice for things like video cameras, because it added $1 in licensing fees.

 

[Neddy]

The BNC, in my opinion, is the most glorious connector ever invented for electronics.

Perfect connection everytime, no issues with accidental disconnection, positive speedy coupling and decoupling. It gives me joy everytime I have to quickly make up combinations of adaptors, Ts and 50R terminators.

If you took away my BNCs, I'd hang up my soldering iron, put all my test gear out on the street and have to take up lawn bowls, gardening, or bass fishing (again). And I wasn't very good at bass fishing. All the gear and no idea.

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Total agree, except I'd (did) go with Lemo conns' and RG178 (~1/8" dia) cables. Performance differences w the larger diameter are only applicable at very long distances (1000s of feet).
The smaller diameter cables and conns are so much easier to deal with, less tangling, less 'drag on gear' and much lighter too.
BNC used where instrumention 'quality' data was required, labs, experiments, etc. or 75 or 50ohm balanced/transmission lines were required for mininal reflections (again,data quality vs. noise).
See

https://www.amazon.com/Reduction-Error-Analysis-Physical-Sciences/dp/0072472278

Home audio, not so much, but a very nice to have (tho there again, if I was going to spec it, I'd much more prefer Lemo's for their Much Easier disconnect - esp on gear you can't see well!)
Having said that, I often had to revert to BNC-RCA adapters. I think I may also have some RCA-Lemo.
Advantage of lemos is their quick Pull sleeve to Disconnect feature - simply pull to release.
Yes, pricey.
A few samples from my collection:

Good questions, as usual!!

 

[xaviescacs]

I have seen and owned plenty of gear that required a hand to hold it in place to push on (or remove) an RCA, even with "normal" RCAs and not these new versions that need vise grips to get on and off.

It's true that RCA cables have a wide range of required force to be plugged and unplugged. That seems strange from a connection standardization perspective. I have a sommer cable with hicon connectors that could be used to walk a dog with an RCA termination on its back. I've have accidentally disassembled them more than once when trying to unplug them by means of rotation.

Perhaps BNC is a better choice after all... but it looks so techie...