DIY balanced audio cable?

Wes -


I've been doing some research on balanced cables and I haven't had a whole lot of luck finding what I've been told is a true balanced cable.


You're probably asking what I mean by "true balanced cable." Here's what I've been told. Some systems have an active differential circuit that, for the circuit to work correctly, needs three conductors - Pos, Neg, and Neutral - in addition to the shielding. The circuit monitors the Neutral and adjusts the signal based on the feedback. The B&K equipment I'm purchasing has a Differential Balanced Circuit.


So far, I've only found one cable supplier, Audioquest, that has a 3 conductor balanced cable. I've found lots of options for a two conductor cable with XLR connectors. However, they use the shield as the neutral leg - which I've been told doesn't work as well.


Depending on your equipment - this may not even be an issue. If you find another, or other, supplier(s) that have a 3 conductor cable please let me know. I haven't purchased the Audioquest yet because they are expensive. However, I'm wondering if the old saying - "you get what you pay for" is true in this case.


Good luck.


Paul

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There is no neutral.


There also isn't any reason for a special cable to allow the device to monitor the level, since the signal originates inside the device, it can sample it there.

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It doesn't know because it doesn't 'adjust' the level. It would be kind of dumb to have your amp arbitrarily adjust audio levels wouldn't it? Thats what the volume control does.


I think you're confused about balanced outputs. A balanced outputs is 6dB higher in voltage then an unbalanced output.

techtv1-


How does it know how long the cable is?


According to B&K - It doesn't know how long the cable is, but it adjusts the signal based on the impedence in the circuit which is in part based on the length of the cable as well as quality of the conductors, etc.


Is the load impedance bridging or matching?


Matching.


Why doesn't any other balanced equipment do this?


If the equipment has an active differential circuit - it does. Otherwise, they simply have balanced connectors.


B&K said if you have any other questions they would be happy to answer them for you - 1-800-543-5252 - Ask for Gerry or George.

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Not for anything but Professional audio has been using balanced XLR's since the ages of dino's (not that long ago but I can tell you it has been a very long time)


for balanced cable


you can run THREE seperate wires (14awg) each and still have a good noise floor. That is the advantage of balanced inputs. If the signal is not in both A+ AND A- it is getting cancelled out. Shielding can be used as ground as has been used for the past 20+ years in the pro audio world


edit: Taking this right from Crown's Amplifier application guide.

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Figgie -


I think I'm going to chalk this one up to "there's more than one way to skin a cat." I've done a lot of reading tonight on the subject and found that the cable construction quoted by you and techtv1 is the prevalent way to build balanced cables. I've copied below the section from Audioquest's Cable guide that discusses their approach to balanced cables. It's certainly different.


Quote: "When a double balanced cable is used with balanced electronics, it usually has XLR connectors on both ends. One conductor is used for each of the two positive signals, and the shield is used for ground. To us, this is a step backwards: the reference ground is just as sensitive to distortion mechanisms as the positive signals and so deserves exactly the same respect. For this reason (and for better performance when used with RCA plugs) all cables from Coral and above are triple balanced.


An XLR plug can make four possible connections. AQ triple balanced cables use the three pins or sockets to connect the reference ground and the inverting and non-inverting positive signals. The case of the XLR is used to connect the shield to chassis ground."


Maybe it's a gimmick, or just maybe, both ways work and one is better than the other. It appears, most people don't subscribe to the theory or know about Audioquest's version of a balanced cable. I don't know how to resolve the issue other than to try cables built in both manners and see if I hear a difference. Although it may be extremely hard, if not impossible, to find cables with the same conductor material etc. with the only difference being the way the XLR's are terminated.


This has been an interesting journey. Not sure where I'm going to end up. If a two conductor cable, terminated in the manner that's been documented/suggested in the numerous articles I've read, works as well as Audioquest's "triple balanced" solution, I can save a lot of money.


Thanks to you and techtv1 for your thought provoking feedback.


Paul