Canare L-4E6S Star-Quad Audio Cable

Discussion in 'Amateur Radio Equipment Reviews' started by W2WDX, Jun 17, 2018.

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  1. W2WDX

    W2WDX Ham Member QRZ Page

    Hi all,

    Having a background in professional audio one product that is a standard in my toolbox is good cabling. Now I'm not talking about audiophoolery here like you find in the high-end audio world or any voodoo magic you find there. I'm talking about engineered systems for broadcasting, recording studio, and live sound applications. With "audio chains" being so popular these days in Amateur Radio, I thought I would review a secret weapon I use to fight RFI and noise issues in my audio chains. While not an Amateur Radio specific product, it is highly advantageous to be using it in our hobby and so I thought a review would be useful to some.

    In my professional work, particularly in live sound concert audio, in the early days we began noticing a significant increase in noise and interference in the miles of audio cable (both microphone and line level) we used at a typical concert. The use of dozens of VHF/UHF wireless microphones, proximity of high-power radio stations near some venues, the rise of cell phones, and even the SCR devices used in stage lighting dimmers were all sources of EMI and noise. We began using better cable to combat this increasing problem. (Nowadays with the rise of digital audio this is less of a problem). So began my use of Canare L-4E6S Star-Quad Audio Cable.

    Canare Star Quad obtains its name from the 4-conductor style construction that minimizes the “loop area” between twists of the conductors. This “double balanced” pairing, reduces susceptibility to electromagnetically induced noise. The improvement in noise rejection is so noticeable that even SCR dimmer noise (stage lighting consoles) is reduced to less than 1/10 the level found in other 2-conductor microphone cables. The signal generated by a microphone during quiet periods can be very low in level, -70dB to -120dB (0.3 millivolts to 1 microvolt). The cable that must carry this signal to the mixer or mic input is very sensitive to Electromagnetic Interference (EMI), Radio Frequency Interference (RFI) and electrostatic coupling of hum and noise.

    This cable is designed for use with microphones but is also excellent for all line-level signals (e.g. mixer to power amps, audio chain to transmitter, etc.). The 4-conductor Star Quad arrangement cancels electromagnetically induced noise from lighting dimmers, fluorescent lighting ballasts and AC power transformers, hash noise from routers & computers, and RF in the shack. Handling noise is prevented by use of cotton filler material. Excellent frequency response is maintained due to special irradiated polyethylene insulation which provides a low capacitance dielectric.

    This cable is for use on balanced audio lines. The wiring to standard "pin 2 hot" applications is critical for this cable to do its magic. Below is a typical wiring diagram for this cable to standard XLR audio connector:

    starquadwiring.jpg

    For our uses in Amateur Radio, the use of "better" cables is a heated debate (frankly I never got that). However, the old "I've been using xyz for 42 years and I never had a problem" mentality is one I have never prescribed to; especially when it comes to audio applications. And now with the broad use of audio devices by amateurs, many of which not designed with proximity to high-level RF fields in mind, the issue of cabling is important; and often overlooked or down played. How many times have you heard on the air, "I'm getting RF in my audio ...". Well ... there ya go. Many times it's poor cabling. So out come the ferrites and we have messy cables with big loops in toroids and we think we have solved the issue. No ... we have not cured the root causes; and in this case using cables less susceptible to EMI/RFI is treating one root cause.

    This cable is not prohibitively expensive and is relatively easy to acquire. One of my favorite sources here in the Northeast U.S. is Markertek. They sell it by the foot @ .99/ft with free shipping (as of this writing).

    For my stations (and in my pro-audio facilities) I use this cable. In my stations I do clip on a ferrite before a piece of equipment that does not have any RF specific filtering on its input, just to act as a common-mode choke for the shield. But never have I had to use big ferrite toroids with feet of cable wrapped up inside it.

    Now you could use this cable as a multi-wire microphone cable carrying PTT and other data. But that's not what we are referring to here. Using it that way does not afford any EMI suppression. It just becomes any standard multi-wire cable. This application is specific to balanced audio, whether we are talking using it for a microphone to a mic pre-amp, or a line level signal between two processors, or from the processor to the audio input of a transmitter. Of course it could be used for line-out audio to an audio amplifier for receive use as well. Anywhere low-level balanced audio needs to be routed, use of this cable helps reduce noise and acts to choke off EMI/RFI interference.

    If you really want to go full-on technical, here's a white paper (in pdf) on the subject prepared for the pro-audio world. It's sort of the seminal paper on the subject in those circles.

    A Technical Paper - Evaluating Microphone Cable Performance and Specifications


    I hope some of you find this useful. Cheers!

    73

    John, W2WDX
     
    Last edited: Jun 17, 2018

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