I have heard hum when XLR cables were used and the solution was to switch to unbalanced cables with RCA plugs and the pieces of equipment being connected were from the same company- they had been used at another place and the problem was caused by an electrician who neither knew why I had asked for the outlets to be wired in a particular way, nor did he care. For consumer equipment, which isn't always true balanced low impedance, it's a waste and totally unnecessary.
There's a way to eliminate noise by using cabling that's often referred to as 'quasi-balanced', which is a twisted pair of wires in the center, surrounded by insulation/dielectric and some kind of shielded. It's also called 'Shielded, Twisted Pair'. The reason it works is covered in the Rane papers under 'common mode noise rejection'.
It's not just a matter of converting the plugs or using an RCA on one end and wiring an XLR at the other- the input/output impedance and signal levels are different for unbalanced high impedance or balanced low impedance circuits and they don't work as planned when one of each is on the ends of the signal chain.
Using the mathematical concept of IFF- IF balanced, low impedance gear is used in the signal chain, it can work well and then, only if the grounding is correct. If the electrical service has grounding issues, it's sometimes possible to lift the ground connection at Pin 1, but this should only be done if the equipment has been designed to handle it. Lifting that connection can sometimes create a lethal problem.
Read these-
Since the Audio Engineering Society has adopted the "pin 2 is hot" standard, what is the correct use for pin 1?
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Balanced vs Unbalanced interconnects and cables, what is the difference? This article discusses both cable types and gives you the pros and cons of each. Use balanced cables whenever you can.
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