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Quad Star Microphone Cable

Or Star Quad Microphone Cable, depending on who is making it.

Star Quad Microphone Cable diagram

Star Quad Microphone Cable diagram

This has been around for quite a while, but many studio/broadcast engineers don’t understand it or don’t use it for some reason. Microphones and mic pickups produce relatively low signals when compared to line level audio.  Most microphone preamps have a gain of +50 dB, which means any noise gets amplified and even small things can become major problems quickly.

Gepco MP1201 Quadstar Microphone Cable

Gepco MP1201 Quadstar Microphone Cable

Under general conditions, most balanced shield twisted pair (STP) audio cable such as the standard Belden 8450 is adequate for stationary microphone cable for short runs.  When cable is not permanently fixed in place, as in hand held microphones, microphones mounted on booms, or other non fixed microphone applications, then flexible cable must be used.  Star Quad cable has better noise specifications than standard flexible microphone cable.

The advantages of Star Quad cable for low impedance microphones (150 ohms) is that the parallel twisted pairs significantly reduces inductive reactance.  In AC circuits, inductive reactance acts as a low pass filter, gradually rolling off as the frequency is increased.  This effect is cumulative, the longer the cable run, the more inductive reactance is added to the circuit.  The result is microphone audio can have smeared or ill defined high frequency audio.

parallel inductance formula

parallel inductance formula

Using two parallel twisted pairs is similar to parallel resistors when it dealing with inductive reactance, it halves the value.

In addition to reducing inductive reactance, the tighter twist found in Star Quad cables reduces the CMRR by about 20 dB.  The Star Quad configuration keeps the conductors in the same relative position to each other as the cable is flexed and moved around.  All of this makes it superior to standard STP microphone cable.

Several companies manufacture Quad Star cables:

  • Belden: 1192A
  • Canare: L-4E6S
  • Gepco: MP1201
  • Mogami W2534
  • Cardas 4X24

The price of Star Quad cables runs about 40-60 cents per foot (more for the Belden, much more for Cardas) if purchased in bulk.  That is about the same range for two conductor mic cables.

As good as this cable is, I don’t think they had this in mind when they made it:

I wonder what the centripetal force on that cable is when the microphone is in full motion. Also, I’d bet that SM58 was none the worse for were after it’s crowd surfing moment.

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