Originally Posted By: XenonMan
If the cable runs are longer than 12 foot or they will be subject to RFI the XLR connectors have an advantage. Other than that they are not needed. However another big advantage is that the connector is mechanically more secure.


Xenon's pretty much right-on here, but there is a wrinkle in all of this that's getting lost...

If the RCA cables are subject to hum from AC mains (RFI is a serious issue to be certain), and you have tried all that you can to reduce the hum (physically separating the RCA cable(s) from the AC cables / mains, having the RCA(s) traverse the (known) AC cables at right angles, and so forth), then the balanced cable is the way to go...with one huge caveat: unless the balanced line is connected to a differential (XLR or TRS) input, then there is no benefit at all to using the XLR (i.e. balanced) approach. All of the noise rejection in a balanced / differential system depends upon a balanced output being fed to a differential input.

So, what I am saying is...if you have hum or RFI issue with an RCA cable (perhaps one going to a subwoofer for example) and the device to which you want to provide a signal does not have a differential input (i.e. it has RCA inputs only), then unless you couple the balanced signal on the XLR cable to either a matching transformer (or an active balanced to single-ended device) and connect that single-ended RCA output to the RCA input of the subwoofer (or whatever), then there is no point in using the balanced approach.

This is why in professional audio gear, most outputs are balanced, and most inputs are differential - either a transformer, or an active (op-amp differential amplifier), and it's why all professional grade microphones have balanced outputs - especially important when you think about the magnitude of a typical dynamic microphone's output, which could otherwise be swamped by induced RFI or hum from adjacent AC mains.


Edited by old_school_2 (05/05/12 04:09 PM)
_________________________
old_school_2 ... the user formerly known as "old_school"
www.immersifi.com
skype: mark.a.jay
email: mark@immersifi.com
linkedin: http://www.linkedin.com/pub/mark-jay/5/82a/237