Star quad cable

Opposite points of the star are connected together at each end of the cable to form each leg of the balanced circuit.

Interference picked up by the cable arrives as a virtually perfect common mode signal, which is easily removed by a coupling transformer or differential amplifier.

The combined benefits of twisting, differential signalling, and quadrupole pattern give outstanding noise immunity, especially advantageous for low-signal-level applications such as long microphone cables, even when installed very close to a power cable.

It is particularly beneficial compared to twisted pair when AC magnetic field sources are in close proximity, for example a stage cable that can lie against an inline power transformer.

[7] The disadvantage is that star quad, in combining two conductors, typically has more capacitance than similar two-conductor twisted and shielded audio cable.

With a 150 Ohm source impedance and 1200 pF load capacitance, the frequency response of this RC circuit is -0.02 dB at 20 kHz.

The star-quad geometry partially cancels the magnetic fields that are produced by the two pairs of conductors.

Because the conductors are always the same distance from each other, crosstalk is reduced relative to cables with two separate twisted pairs.

Star-quad cable intended for use with a single two-wire circuit or two two-wire circuits. It is often used with microphone signals in professional audio .
Star-quad cable cross-section
Star-quad exploded view showing the geometric centers of the dual-conductors used for each leg of the balanced line.
To achieve magnetic immunity, geometric centers of both dual-conductors must be aligned to a common point.