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Instrument Cable testing / measuring

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  • #1

    Instrument Cable testing / measuring

    I noticed that some of my old road-worn guitar cables colour the sound when played with a guitar.
    • A budget 7.5 metre one branded LIVE WIRE noticeably attenuates the signal, and knocks off a bit of treble.
    • Three van-damme Classic add some crackle distortion on top of plucked low notes like a E, A or D open string.


    I wondered what approaches exist to test, or rather measure the performance of, cables other than just by ear?

    Any thoughts and ideas?
    Tags: cable
  • #2
    Usually the treble loss is caused by the capacitance of the cable. It would be spec'd as pF per foot. Some folks find the low capacitance cables too bright, others like them. Because it is pF per foot, the length makes a big difference.
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


    ​

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    • #3
      Originally posted by mikeydee77 View Post
      I noticed that some of my old road-worn guitar cables colour the sound when played with a guitar.
      • A budget 7.5 metre one branded LIVE WIRE noticeably attenuates the signal, and knocks off a bit of treble.
      • Three van-damme Classic add some crackle distortion on top of plucked low notes like a E, A or D open string.


      I wondered what approaches exist to test, or rather measure the performance of, cables other than just by ear?

      Any thoughts and ideas?
      If the cable has high resistance from a bad connection, then that can form a high cut filter with the cable capacitance. What is the issue? If the cable is bad, throw it away.

      Comment

      • #4
        Rolling chairs is usually the big cable killer.
        Like Mike said?
        Measure the cable, if just bad at the ends, cut off a few inches and re-solder.
        I do it all the time, also heat shrink over the end is a big time cable saver!
        T
        "If Hitler invaded Hell, I would make at least a favourable reference of the Devil in the House of Commons." Winston Churchill
        Terry

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        • #5
          It's worth a shot (if you have the time) to feel and visually inspect every inch of a suspect cable. 90% of the time I can find a really bad kink, hole punched in insulation, etc. Just by rolling it slowly in my fingers. Also, gently flex it while plugged in and turned on every inch or so, any crackles or noises tell you where the bad spot is.

          And, who can forget that black conductive layer they put under all the shields now? Damn it to Hell! If so much as a smidgen of that crap touches as much as a single strand of signal wore, you're in for a world of hurt. I can't really efficiently explain how to avoid it online, but just know - the black wrap stuff is very flexible, stretchy, and melts very easily. Trying to dodge it adds many long minutes to a cable repair. Meter your cable from tip to sleeve - anything less than wide open circuit is trouble. I've gotten everything from dead shorts to 10Megs; both cause the same problem, to varying degrees.

          Justin
          "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
          "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
          "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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          • #6
            Thanks for the ideas - by the way I wasn't planning on keeping these cables particularly but I am going to investigate further just to learn something.

            I have tested these cables with a meter tip to sleeve and I got 200K, 15K (both 3m leads) and 1.5K (on the really bad 5m one). For comparison a lead that I consider good reads as 2M ohm which is a Klotx AC110 cable.

            As suggested I usually salvage old leads by chopping off 6 inches to a foot on the basis that is where the strain is but given the comments about the conductive shield and cable crushing which I am definitely responsible for I will have to rethink that approach.

            I also found somewhere someone claiming that they have been making their leads more robust by filling the void between the solder tags with hot melt and quickly sliding over heatshrink whilst still setting thus creating a DIY molded plug.

            I have just bought some new leads in case anyone is coming to my next gig and was worried about suffering crackly bass lines!

            Mike

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            • #7
              Long ago I discovered that bad solder work can add a ton of tone-sucking capacitance so nowadays I always check cable capacitance (tip to sleeve) with an LCR meter.

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              • #8
                Originally posted by mikeydee77 View Post
                I have tested these cables with a meter tip to sleeve and I got 200K, 15K (both 3m leads) and 1.5K (on the really bad 5m one). For comparison a lead that I consider good reads as 2M ohm which is a Klotx AC110 cable.
                They all look bad to me. The two 4m cables I made twenty years ago (Neutrik plugs Van Damme cable) measure open circuit tip to sleeve on the 200M meter scale. Capacitance measures 500p. Sleeve to Sleeve and tip to tip measure 0.2 ohms and 0.3 ohms.

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                • #9
                  One thing to be careful of when testing anything on high resistance scales is to make sure that your fingers are not touching the probes. Your body will actually have some resistance and capacitance skewing the results.
                  "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

                  Comment

                  • #10
                    Originally posted by The Dude View Post
                    Your body will actually have some resistance and capacitance skewing the results.
                    I measured around 2M for 'me' yesterday when I was measuring the cables. Perhaps that is where the the 2M of the 'good' cable came from in post #6?

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