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[Tristan Ferguson]

I am picking up a reel of balanced line level signal cable and I am wondering (more for the sake of curiousness) if anyone thinks quad cable could ever offer a benefit or would ever be necessary for line level signals. I understand a line level signal is much higher than a microphones (+120 dbu?) but I'm mostly just curious.

Thanks!

[Jordan Wolf]

Well, as I understand it, professional line level is +4dBu or 1.23 Volts RMS.

Star-quad cable is good for shorter runs of cable and patching in racks.  I've always heard it is best to avoid long runs of it, though.

I don't know how line level is affected since the signal is MUCH stronger than mic level, but I'm sure a number of folks will pop in and share their knowledge.

[Geoff Doane]

Quad cable is better at rejecting external noise than an equivalent single pair cable.  

If the chance of external noise is low, quad cable may very well be "over kill".  But many people prefer to play it safe and use quad cable anyway, just in case they run into a situation where that noise could be a problem.  With the portable situations that most of us deal with, external noise is a variable that we have no control over, and quad cable becomes an "insurance" policy.

Quad cable may also be a little bit more robust than regular, and if one conductor does break for some reason, the cable will still work.

The downside is that quad cable has roughly twice the capacitance of equivalent single pair cable.  That means you can only run half the distance before the top end starts to roll off, but that distance will still be several hundred feet, even under worse case conditions.

Personally, I wouldn't use quad inside a rack, because the connections are more difficult, and the ratio of connections to cable length is rather high in this situation.  Foil shielded, single pair cable has always worked fine for me.  For my money, the cable from microphone to stage box, is the most effective use of quad cable.

GTD

[George Friedman-Jimenez]

The 15 foot quad mic cables I have, from EWI, don't handle or coil as well as regular mic cable, exactly what Mark told me when I bought them. I use them in a studio which is (electromagnetically) very noisy, but not on stage.

[Mike Kivett]

I've been buying some of the quad cable from EWI as well, and have had no trouble coiling or maintaining them.  

They are a bit more robust feeling, and are not (for lack of a better term) as "slinky" as normal cables.  They wrap up just fine with an over/under and a tie line.  

That said, one of the rigs I normally work with has a mic cable box that is totally full of those Rapco Hog cables, which are thick and heavy things.  After wrapping a trunk of these, the EWIs seem light and manageable.  

[Tristan Ferguson]

"Well, as I understand it, professional line level is +4dBu or 1.23 Volts RMS."

My mistake. What I meant by "+120 dbu" was "plus 120 dbu over mic line" which I believe is a -120 dbu signal. I could be wrong.

Being that my situation is with portable sound, I've heard that I should avoid the foil shielded cables because they are not as flexible and the foil shield can crack and break after too much bending.

That being the case, the only braided shielded 2 channel quad cable I can find (I NEED to keep the cables adjoined into stereo pairs for the sake of simplicity. I hate tangled cables) is Canare L-4E3-2P ( http://www.canare.com/files/Page%2038%20canare_catalog12_web .pdf) and it's effective gauge is 25 awg per pair of conductors. Is that too thin? I usually find most balanced signal and mic cable to be of 22-24 gauge. There is Canare L-4E4-2AT at 22 gauge per pair of conductors, but alas it has a foil shield.

Thanks for the help.

[Charlie Jeal]

Tristan,

Don't waste your money buying starquad cable unless you are working in an area with a very high level of electromagnetic noise then you don't need it at all. FWIW it was designed with TV outside broadcast use in mind. Just spend the extra bit on some high quality 2 pair cable such as Belden or Canare or even Mogami if you're feeling flush.

Line level in its strict definition is 0.77RMs and relates to the use of old style 600 Ohm telephone lines. I think you may be getting the +4dBu from the fact that on professional standard meters the OdB mark is equal to +4dBu unless you are dealing with a lot of digital gear in which case OdB can mean OdBFS which can be between +18 and +26 dB in relation to 0dB as +4dBu.

You dont actually say whether you are talking about balanced or unbalanced line leve either.

Charlie

[Geoff Doane]

Tristan Ferguson wrote on Thu, 09 April 2009 12:46

Being that my situation is with portable sound, I've heard that I should avoid the foil shielded cables because they are not as flexible and the foil shield can crack and break after too much bending. That being the case, the only braided shielded 2 channel quad cable I can find (I NEED to keep the cables adjoined into stereo pairs for the sake of simplicity. I hate tangled cables) is Canare L-4E3-2P and it's effective gauge is 25 awg per pair of conductors. Is that too thin? I usually find most balanced signal and mic cable to be of 22-24 gauge. There is Canare L-4E4-2AT at 22 gauge per pair of conductors, but alas it has a foil shield. Thanks for the help.

Foil shields are usually avoided for cables that will be routinely handled by performers on stage, but virtually all of us use them for "snake" cables (multiple pairs).  The other pairs (or quads) and the generally overall larger size of the cable seem to help prevent the foil shield from deteriorating too quickly.  The importance of the shield is also overrated.  An overall shield only helps prevent RFI (radio frequency interference).  It won't do a thing for lower frequency noise, or crosstalk, which is where a well twisted pair or quad will prove its worth.  Unshielded CAT 5 cable is actually used to carry audio in many broadcast facilities, and performs perfectly for this task.

Wire gauge is also not much of a factor in today's low source impedance, high load impedance environment.  For microphone or line level signals, capacitance of the cable is by far the dominant parameter affecting audio performance.

GTD