Are there many people using BNC out there? or RG6 Quad Shield? - diyAudio
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Old 2nd December 2012, 10:54 AM   #1
freax is offline freax  Australia
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Default Are there many people using BNC out there? or RG6 Quad Shield?

I just finished making a pair of BNC quad shield cables and I was wondering if there were many people out there rocking with BNC and Quad Shield Coax for Line Level applications?

Benefits of BNC over RCA:
#1 They are certianly a lot cheaper than most high end RCA cables and have a much more rugged connection than RCA having the center conductor protected.
#2 There is also a great deal less variation in quality compared to RCA which has been remade ad-infinitum to the point that no one can standardize properly.
#3 BNC connects the shield first before the tip, another benefit.
#4 BNC to RCA adaptors and vice versa are widely available and cheap.
#5 Higher bandwidth, lower ingress of noise.
#6 At frequencies below 10 MHz the impedance mismatch between a 50 ohm connector or cable and a 75 ohm one has negligible effects. (http://en.wikipedia.org/wiki/BNC_con...#Compatibility)
#7 A beautiful pure copper 18 AWG center conductor with 4 shields, 2 braided and 2 foil.
#8 Much lower impedance connection vs RCA = lower noise floor.

These cables are going inbetween my DAC and my soon-to-arrive KT88 SE kit amplifier, They measure on my multimeter as 000.3 ohms (or 000.0 ohms, unregisterable) for 3 meters of coax or shield. without any inter conductor short, I'm old hat at terminating quad shield to F connectors so this was a cinch.

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Last edited by freax; 5th December 2012 at 09:29 AM.
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Old 3rd December 2012, 07:27 AM   #2
qusp is offline qusp  Australia
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they dont have heatshrink where you live? =)

people have been using BNC in place of RCA for EONs, in fact Erno Borbely has recommended their use for years.

on the other hand, the 'much lower impedance' is unlikely to make any difference to audio performance, particularly with a tube amp
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Old 3rd December 2012, 07:44 AM   #3
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Quote:
Originally Posted by freax View Post
I was wondering if there were many people out there rocking with BNC and Quad Shield Coax for Line Level applications?

Probably not so many. If you are doing this in order to optimise perceived sound quality i see some issues. Unless you forgo using rca-terminated equipment you will be forced to use either horrible or very expensive conversion kits. And there goes your "low-impedance".

Not all of us are convinced in the sonic superiority of screened cable for line level use. And especially if the screen is used to carry signal.

Not too sure about the superiority of friction connection to between the screen and the connector either. Even less sure about the outer connector metal composition.

If you hate RCAs, why don't you go for XLRs? Much better for audio methinks.
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Old 3rd December 2012, 08:17 AM   #4
freax is offline freax  Australia
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I'm not using BNC for any perceived sound quality improvements, I'm doing it because I think its finally time to put RCA out to pasture on my equipment and I need a replacement for unbalanced inputs and outputs on all of my devices.

I hate XLR too, but it has its place, I have a desk mike here that is XLR, but drilling a small bnc hole is much easier than a big xlr socket, less metal cut out.

I can make really small projects and use bnc whereas xlr wouldnt fit, even if the coax moves the amplifier or preamp off the table, at least its getting a big bit of 18 awg copper to it that is heavily shielded.

quad shield when bought from the right place is high quality and cheap and very very easy for me to terminate, aswell as being able to find it in almost any hardware store so if in an emergency i need to replace a cable i can.

I'm not sure how well xlr will stand up to shielding against radio transmissions, If i ever want to get into ham radio then I don't want my precious audio equipment being damaged by a coax transmission line that has an RF leak, or my tube amplifier amplifying at RF frequencies and taking out one of my tweeters, at least with coax I can reduce the chance of this occuring at the most sensitive and susceptible areas of a circuit.

I listen into shortwave, what happens when that xlr cable which is carrying digital from my heavily RFI shielded computer is layed down near-to my shortwave radio antenna coax?
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Last edited by freax; 3rd December 2012 at 08:25 AM.
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Old 3rd December 2012, 08:24 AM   #5
qusp is offline qusp  Australia
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it would handle it better than your BNC, provided you arew actually using balanced gear that is. because it has CMRR as well as having a completely separate shield. with RCA and BNC when used in its place, shield and ground are the same thing, what point is your quad shield when its directly connected to your signal ground?
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Old 3rd December 2012, 08:32 AM   #6
PMA is offline PMA  Europe
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I wish BNC'c were used instead of RCA CINCH in audio ...

Not only for much better shielding, but also for defined geometry and they 1st connect ground and then live. This is extremely important!!
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Old 3rd December 2012, 08:36 AM   #7
freax is offline freax  Australia
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an interesting viewpoint, though I have no balanced equipment and I don't know of anyone else who does either, not in the home anyway, good luck finding well shielded cable for xlr too.

I don't believe in using heatshrink unless its necessary, like for example in very high voltage circuits, one tube of heatshrink might be $2 and for low voltages I've found that a simple layer of duct tape does just as good and enables me to rip it up and do a repair and reuse the tape again or simply put new tape down, and duct tape is much cheaper in the long run to simply have the duct tape handy.

For making test leads for example though I would use heatshrink.

I also forget to put the heatshrink on the wire first far more often than I remember to do it before I start stripping. haha. I'm too eager I guess.

This thread is also about replacing RCA with something thats slightly more modern for unbalanced equipment.

I've also had rca center conductors snap off before, its rare but it can happen.

The only downside I can see so far with going with bnc is that its not colour coded.

the most common setup is to connect pin 1 to the signal ground which is the wrong way to do it according to this website: Sound System Interconnection

so whats the best method? with bnc it connects the signal ground to the same chassis ground, and if you have problems with this then its fairly easy to find a washer and put it behind the bnc socket to shield it from the chassis inorder to float the shielding.

with bnc this is a lot easier, strip the coax, put the coax in, crimp it, done.
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Last edited by freax; 3rd December 2012 at 09:02 AM.
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Old 3rd December 2012, 08:45 AM   #8
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Buy insulated BNC, there are hundreds of them.
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Old 3rd December 2012, 09:01 AM   #9
freax is offline freax  Australia
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ah yes, there are those too if it becomes necessary.

a few good responses from this thread, didn't see it when I searched: Using digital interconnect as analog interconnect
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Last edited by freax; 3rd December 2012 at 09:28 AM.
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Old 3rd December 2012, 02:21 PM   #10
GM is offline GM  United States
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I use BNC on Mcintosh tubes and quad shielded for antenna feeds to OTA digital TV converter boxes to TVs and been very pleased with its 480i up converted, so recently made 15 ft component video cables with it in an attempt to improve PQ and couldn't believe the difference on DVD, and especially 1080i BD, Vs shorter 9 ft consumer 'high def' cables from 2002. I know I'm in a very high electronic noise area, but had no clue it affected consumer interconnects this much.

Obviously, they need a lot of room to route them compared to consumer cables, but as time permits I'll be converting all my interconnects with it.

Note that this is through a 65" RPTV viewed at THX reference distance, so smaller screens and/or further away the difference will diminish to zero for most folks at around three screen width's distance, so not a worthwhile tweak for everyone.

Hopefully it will improve audio at least as much, but it will be awhile before I have time/$$$ to rebuild my audio system.

GM
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