Q. Do your QED XLR cables support balanced audio?
Answer:
Yes, we can confirm that both our
analogue and
digital XLR cables are designed to support
a balanced output device on one end and a balanced input on the other. Using our unique Tri-Conductor
™ technology, utilising a
third conductor which is integrally twisted alongside the signal pair to
carry the ground return currents.
Normally, a balanced XLR contains hot, cold and screen, where the screen forms an electromagnetic shield which protects from external high current noise signals (such as mains hum) only. The common mode rejection of the cable is quite good, as long as hot and cold both have the same impedance to ground, but there is not such effective protection from external high voltage spikes afforded by the screen. This is because it is connected at both ends, and the capacitance of the hot and cold w.r.t. ground is not identical.
The Reference XLR 40 contains hot, cold, ground and screen, with the screen connected at the sending end only. This provides the advantage of reducing signal to ground capacitance to vanishingly low levels, thus affording the cable improved common mode rejection of mains hum pickup over ordinary "hot and cold screen" cables. In addition, the screen then acts as an electrostatic shield screening the cable from external high voltage noise with the integrally twisted ground conductor providing improved electromagnetic screening due to the improved common mode rejection afforded by the balanced capacitance to ground.