as above. pros/cons of connecting/not connecting?
I seemed to recall (many many years ago) some cable manufacturer sells RCA cables where the ground pin is only connected on source side.
thanks!
I seemed to recall (many many years ago) some cable manufacturer sells RCA cables where the ground pin is only connected on source side.
thanks!
Yes, see the AES48 standard. The standard is quite expensive, but you can find drafts and earlier versions for free, like https://www.aes.org/standards/comments/drafts/aes48-xxxx-190121-cfc.pdf
A] Some experts suggest not connecting the shield at the receive end of an XLR line level interconnect. But this will degrade high frequency RF interference. So they use a hybrid connection at the receive end. This is a small RF capacitor.
b] All microphone cables need the shield connected at both ends.
So the complicates things for a pro. They would need one box of interconnect cables and another box of mic cables.
b] All microphone cables need the shield connected at both ends.
So the complicates things for a pro. They would need one box of interconnect cables and another box of mic cables.
Without the connection from Pin 1 to Pin 1 you risk blowing the differential input as the common-mode voltage may exceed the limits of the receiver.
As pointed out above, the recommendation is to connect Pin 1 to Pin 1 through the shield. Connect Pin 2 to Pin 2 and Pin 3 to Pin 3 using the signal pair (or star quad if you want to be fancy).
Some fancier RCA cables run a twisted pair inside of a shielded cable. The pair is used to connect signal and ground. The shield is then unterminated at one end. That's a misguided way of pretending to avoid a ground loop. A differential link 'moves' the ground loop (which is unavoidable) outside the signal path so any ground current won't impact the signal quality. That along with the rejection of common-mode signals/interference are the main points of a differential link.
Tom
As pointed out above, the recommendation is to connect Pin 1 to Pin 1 through the shield. Connect Pin 2 to Pin 2 and Pin 3 to Pin 3 using the signal pair (or star quad if you want to be fancy).
Some fancier RCA cables run a twisted pair inside of a shielded cable. The pair is used to connect signal and ground. The shield is then unterminated at one end. That's a misguided way of pretending to avoid a ground loop. A differential link 'moves' the ground loop (which is unavoidable) outside the signal path so any ground current won't impact the signal quality. That along with the rejection of common-mode signals/interference are the main points of a differential link.
Tom
In my (not so) humble opinion, this should be handled in the equipment, not in the cable.
Tom
AES48 compliant equipment is by design meant to be used in installations with lots of ground loops, so you can just connect the shield on both sides, which is indeed best for RF shielding.
For equipment that is not AES48 compliant, it indeed makes sense to just decouple the shield on the receiving side, if the grounds are already connected by some other path (protective earth, for example). You can either use a small-size 100 nF or so capacitor or a capacitor in parallel with a 220 ohm resistor. The latter option has the advantage that it keeps working when the other ground connection is removed.
Unbalanced equipment with protective earth is even worse, but fortunately that's off topic.
Edit: if the construction of the equipment allows it, you can of course modify equipment that is not AES48 compliant to become AES48 compliant.
For equipment that is not AES48 compliant, it indeed makes sense to just decouple the shield on the receiving side, if the grounds are already connected by some other path (protective earth, for example). You can either use a small-size 100 nF or so capacitor or a capacitor in parallel with a 220 ohm resistor. The latter option has the advantage that it keeps working when the other ground connection is removed.
Unbalanced equipment with protective earth is even worse, but fortunately that's off topic.
Edit: if the construction of the equipment allows it, you can of course modify equipment that is not AES48 compliant to become AES48 compliant.
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thinking a use for the canare star-quad cable I was going to use for DIYing USB cables 😀
Bill Whitlock, retired Jensen Transformers has a very different viewpoint in many of his papers and seminars.
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In pro audio, sometimes un-shielded bonded-pair CAT cable is used for line level XLR interconnects.
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Jim Brown retired Audio Engineering Society EMI/RFI committee has a very different viewpoint in many of his papers and seminars.
They can have whatever opinions they want. AES48 is pretty clear...
Tom
Tom
Building (well more thinking how to build it) a source device with balanced/XLR outputs and I want it to be AES48 compliant but just thought about the color code of pin 1 wiring. The AES48 papers do not say anything about color codes do they?
Stupid question maybe but I am curious.
Stupid question maybe but I am curious.