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Old 6th March 2003, 10:57 PM   #1
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Default BNC connectors a ggod alternate to RCA

I was wondering if anyone uses BNC connectors instead of RCA? I notice they are readily available in silver plate and are used in lab setups for measuring cell memebrane potentials and currents. Seems they would make a good alternative to RCAs.

Anyone see a reason not to use them? They can be made at home with various wire and the connect disconnect is very nice.
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Old 6th March 2003, 11:06 PM   #2
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Go for it, should make a nice, modern scientifico-industrial look to your setup (providing they are in view that is ).

Problem, of course being that nothing else uses them, so you'd have to make/buy a lot of connectors and adapters.

Don't forget to match impedance! There's nothing worse than 257Hz going through 50 ohm coax with a 4:1 VSWR!!! (If you don't know what I'm talking about, then the purpose of coax is lost on you. *No offence intended in that statement*)

Tim
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Old 6th March 2003, 11:29 PM   #3
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BNCs, and other RF types too, make excellent connectors, and are often available in quality construction and materials that simply embarass audiophile masturbatory products for quality and price. And no matter how well you make an RCA, it's still a POS connector.

On previous single ended systems I've used BNCs exclusively, both because of the nice construction, and the fact that I usually got them from work for free. My system is balanced now so XLRs do fine.

The only problem is as Tim mentions, compatability with other "pre-made" cables, but as you're a diyer, make your own. They don't <i>need</i> to be coax either.

Quote:
Originally posted by Sch3mat1c
Don't forget to match impedance! There's nothing worse than 257Hz going through 50 ohm coax with a 4:1 VSWR!!! (If you don't know what I'm talking about, then the purpose of coax is lost on you. *No offence intended in that statement*)
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Old 6th March 2003, 11:37 PM   #4
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The males are a bitch to attach to cable. But the reliability and sonics are impeccable. I wish the audio industry had standardized on BNCs.

Sch3: I don't understand what SWR has to do with anything, since the wavelengths involved are enormously larger than the length of any reasonable cable. Let's see, 16 meters is about 20 MHz, so the wavelength at 20kHz is going to be about 16,000 meters. That's a pretty hefty wire run. Impedance matching is an issue at RF, not audio.

Trivia: Anyone know what "BNC" stands for?
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Old 6th March 2003, 11:49 PM   #5
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Quote:
Originally posted by SY
Trivia: Anyone know what &quot;BNC&quot; stands for?
Bloody Nice Connector

Actually British Naval Connector, although one engineer once tried to convince me it was Bayo - Net Connector.
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Old 7th March 2003, 12:13 AM   #6
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SY: you are obviously forgetting just how high the audiophile's golden ear extends to. (Why would anyone bother mentioning their amp does DC to 10MHz anyway?)

I seem to remember Bayonet Naval Connector from an old Electronics Now Q&A. They also mentioned that nobody seems to know just what it is...

Oh yeah. If RCA is crappy, why is it used on TV hookups - look inside, between modulators and such. Some monitors too, old ones at least.

Tim (suprised nobody's yet used 300 ohm parallel wire for interconnects: ** lowest capacitance cabling known to Man ** )
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Old 7th March 2003, 12:42 AM   #7
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Default also consider lemo!

hi

if you are considering alternatives to the ubiquitous RCA in audio, don't forget lemo connectors! (BNC=ancient technology!)

especially appropriate for small signal transfers - we use them in the lab all the time for propagating mV level signals at a few MHz over ~10meter runs.

some advantages of LEMO - airtight, i.e. no possibility of long-term oxidation of the exposed conductor, come in the right sizes for direct adaptation to various co-ax recipes (belden 89259 and friends).

disadvantages are high cost (unless you get some from work , need access to special crimper tool to get them to crimp right: don't even think about buying a crimping tool (the last one we bought cost $450!)

cheers-
pradeep

ps: AFAIK, all the megabucks equipment sold by mark levinson and krell uses LEMO interconnects.
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Old 7th March 2003, 12:42 AM   #8
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Quote:
Originally posted by Sch3mat1c
Oh yeah. If RCA is crappy, why is it used on TV hookups - look inside, between modulators and such. Some monitors too, old ones at least.
Because it's far cheaper to roll two pieces of flat metal to form the connectors than it is to use a BNC. The actual measured performance of many of the modulators in a TV is poor, and they are built to absolutely minimum cost. If it "works", they use whatever is cheapest. Look inside a Broadcast facility and you won't find too many RCAs.

Quote:
Tim (suprised nobody's yet used 300 ohm parallel wire for interconnects: ** lowest capacitance cabling known to Man ** )
I prefer single stand to stranded cables, so it's easiest (and cheaper too) to make something similar. Roll out a length of packing tape on a flat surface, and lay two runs of magnet wire as wide apart as is practical for you. Add another strip over the top and press together. You need two people to do it, but it's easy, simple and cheap, and (if such is your wont) you can even set the characteristic impedance of the cable over a range.

I've used cables like this for audio before and it works fine. Having a balanced system I now use a simple loose triplet braid of magnet wire or tefzel. I live in a rural area so RFI is definitely not an issue.
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Old 7th March 2003, 12:52 AM   #9
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I can tell you're a young guy, Tim. 300 ohm as interconnect was a big fashion tweak about 10-15 years ago.
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Old 7th March 2003, 12:56 AM   #10
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Default Re: also consider lemo!

Quote:
Originally posted by psarin
if you are considering alternatives to the ubiquitous RCA in audio, don't forget lemo connectors! (BNC=ancient technology!)

especially appropriate for small signal transfers - we use them in the lab all the time for propagating mV level signals at a few MHz over ~10meter runs.

some advantages of LEMO - airtight, i.e. no possibility of long-term oxidation of the exposed conductor, come in the right sizes for direct adaptation to various co-ax recipes (belden 89259 and friends).

disadvantages are high cost (unless you get some from work , need access to special crimper tool to get them to crimp right: don't even think about buying a crimping tool (the last one we bought cost $450!)

cheers-
pradeep

ps: AFAIK, all the megabucks equipment sold by mark levinson and krell uses LEMO interconnects.
Hi Pradeep,

I'd like to use LEMOs, but the objections you raise re cost and the crimper have put me off in the past. However RS have solder bucket versions at about 5x the cost of Neutrik XLRs (expensive, but not too bad, cheaper than Cardas RCAs) so I may add some (5 pole 2B's) into the chassis of my new preamp for the phono inputs. Line level can stay XLR.

I know ML used to use them, but I don't think so any more. Not sure about Krell

Cheers
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