Simple in concept, important to understand. Knowing exactly what to look for when using a cable tester can make all the difference when the time comes; Whether that's in the lot before a performance or taking inventory at the end of the season. Not all cable testers are made equal, though. Some have more connector types than others, meaning you could be caught off-guard if your tester isn't compatible with every type of cable you use in your audio system. But no matter the make or model, if you deploy an audio system with your ensemble, this handy tool is one of the most valuable assets to have in your audio toolkit.
In this article, we'll go through a few thoughts that will help you become a cable testing pro.
Know Thy Connector Types
As mentioned above, not all cable testers are the same, particularly when it comes to the number of connector types they're able to test. Some cable testers are smaller in build and are only able to test the most essential connector types. The Behringer CT100, for example, is able to test XLR, 1/4" TRS, 1/8" TRS, TT TRS, RCA, and MIDI cables; Only two of which (XLR and 1/4" TRS) are of major significance to us in the marching arts.
The Hosa CBT-500, on the other hand, is able to test just about every major type of cable/connector seen in use within the marching arts. The ability to test SpeakOn (both NL4 and NL8) and Ethernet is particularly useful.
What The Lights Mean
The job of a cable tester is to tell us whether or not signal is being successfully transmitted from one end of a cable to the other. It accomplishes this by sending an electrical signal through each of a cable's internal wires and indicating the status with some type of LED light.
Sweepable Knob
Some testers utilize a sweepable knob in which the internal cable wires are tested one at a time. The Hosa CBT-500 is a great example of this. Since this tester has the ability to test ethernet cables, it has eight pairs of LED status lights. The first three sets of lights will likely be used more than the others, but we still have to check each pair one at a time.
And indicate possible issues. (The exception here being unbalanced 1/4" TS cables, see below.)
All At Once
Others, such as the Behringer CT100, are designed to only test three wires and indicate the status of those wires all at once, making the task of checking XLR and 1/4" TRS cables much faster.
Testing Unbalanced 1/4"
A strange thing happens when testing unbalanced (TS) 1/4" cables. Cable testers are largely designed to test balanced cables, meaning that when we plug an unbalanced cable into the tester, two of the testers' internal connection points touch the one sleeve on the cables' connector. As a reminder, these are the 1/4" cables with a single ring on the connecter, giving them a tip and sleeve (TS). As a result, the status indicator LEDs might look wrong at first glance.
Pictured above: Testing an unbalanced 1/4" TS instrument cable
Adapter Cables
It is possible to test an adapter cable, such as a 1/4" to XLR cable, with most cable testers. The connectors of a tester are often interconnected inside the chassis, which is what allows us to test a cable with different connectors on each end. The key here is to make sure that the cable has balanced connectors on each end. The status indicator LEDs might show some strange configurations if not.
Cable "Sniffers"
Made by SoundTools, cable sniffers are a different type of tester that's comprised of two halves. Each half of the tester connects to each end of an XLR cable and uses the familiar LED lights to indicate the cable status. The great thing about this type of tester is that it allows us to very easily test cables that are zip-tied or velcro-strapped to marimbas and vibraphones without removing them. However, it's only designed to test XLR cables and another "normal" cable tester
would still be recommended for testing your other cable types.
Use A "Control" Cable
For those without a cable sniffer, fear not, for testing marimba and vibraphone cables is also possible with the use of a regular tester and 'control' cable. But what is a control cable? It's simply an extra cable you have on hand that you know is in working condition. The idea here is to connect the control cable to either end of the keyboard cable, thereby extending its length enough to plug both ends into the cable tester. I carry a control cable for testing with me as a part of my audio toolkit and it's come in handy more times than I can count.
Final Thoughts
At the end of the day, cables testers are hopefully not something that are used everyday by educators. But this perhaps highlights the importance of brushing up on how they're used, what they can do and being comfortable putting them to use.
Be sure to get in touch with us to order a cable tester for your program if you're just starting to build your audio toolkit and to order new cables to replace the ones your cable tester has deemed out-of-order. Microphonic Designs is proud to offer audio products in addition to our services and would love to help you acquire the sound gear you need.