DIY audio cable tester - Page 1
Forum section: electronics / projects

author: labjr
author_rank: Frequent Contributor
timestamp: December 16, 2018, 05:27:25 pm
content: I've started helping a local band with their sound system and running into a few technical problems with running dozens of cables. Does anyone know if there's a circuit for a DIY audio cable tester? I've seen some simple continuity testers, but I want to be able to check balanced XLR cables for shorts and phase reversal too. Looking for a simple but innovative design with a few LEDs which doesn't require switches and fancy circuitry. Thanks.

author: Mark Hennessy
author_rank: Frequent Contributor
timestamp: December 16, 2018, 05:38:38 pm
content: I've done a few DIY things like this in the past, including cat5 and speakON cables, but it's really hard to justify doing a DIY project when you can buy something like this:https://www.amazon.co.uk/Behringer-6-In-1-CT100-Cable-Tester/dp/B000CCIVCAI doubt you could buy all the connectors you need for that. It's not normally as cheap as £15, but even at the regular price (more like £25 IIRC) it's still excellent VFM. I use them all the time.If you want to go down the DIY route, you just need an oscillator and a 4017 plus some LEDs. But no-doubt someone will suggest an Arduino and a colour TFT screen

author: cdev
author_rank: Super Contributor
timestamp: December 16, 2018, 05:50:25 pm
content: My audio problems often have turned out to be crappy electrical connections due to crappy connectors and analog cables which are commonly used on our increasingly miniaturized audio equipment. Having an audio cable tester is super useful and I agree, a nice tester is almost essential in sound work, but watch out for intermittent connections.Balanced cables have an inherent advantage. Unfortunately, grounding on equipment can still cause issues with balanced audio hookups although its much reduced.Most of my gear uses the unbalanced RCA and stereo miniplugs. These cables need cleaning with IPA and even something like 'Deoxit' from time to time.Also, often they would test okay but still have issues because the grounding is not so good, in other words, ground potentials of different pieces of equipment purportedly 'grounded' via the shield of the cheap audio cables, is not a good one, with several ohms being measured. One quick and dirty thing you can do is add an additional connection between your pieces of equipment in the form of a thick enough wire (to lower the resistance to the lowest practical levels- the thicker the wire the lower you can get it- with screw lugs well attached to both ends.This wire should not have any extra distance in it - as its purpose is to reduce the potential difference that causes 'ground loops' it should run right alongside and be exactly the same length as the audio cable - next to the audio cable, and on both ends with no additional loops, affix it to the hopefully metal case of both pieces of equipment with flat headed screws and lock washers. If either of your pieces of equipment lack cases, solder a connection to the PCB ground plane right near the audio input and use that. Verify that the resistance between the two cases is now very low.

author: labjr
author_rank: Frequent Contributor
timestamp: December 16, 2018, 06:00:33 pm
content: Quote from: Mark Hennessy on December 16, 2018, 05:38:38 pmThat's neat. However, I don't think it has to be overly complicated with microprocessors and oscillators etc. Just a well a thought out simple circuit which will satisfy all test conditions. Thus mostly simple logic done with a few LEDs and resistors.

author: Mark Hennessy
author_rank: Frequent Contributor
timestamp: December 16, 2018, 07:45:19 pm
content: It can be as simple as a rotary switch and some LEDs. I have one of those at work...If you don't want to manually turn the switch yourself, an oscillator and 4017 solution is really very simple. Here's an example:http://www.frankshospitalworkshop.com/electronics/diy-lan_cable_tester.htmlBTW, the Behringer has an intermittent detector. Press Reset and wiggle the cable - a momentary open will be latched for you to see. Quite useful, as it responds quicker than you can see with a simple LED.