We have received a number of inquiries as of late about a strange phenomenon; “Hey, what is going on if I am connected to a monitor system and I get a shock through the connector on my earpiece?”

Well, it is a bit of a lengthy explanation, to get the full scope. The quick and dirty is; There is a grounding problem in your sound system.

The full explanation is like this. First off, this will never happen with a wireless monitor system. You will only experience this when hardwired to a system like an Aviom or a hardwired beltpack like the ones from Shure. The reason being is that there is no ungrounded voltage potential in a wireless system. The only voltage that your earpieces should see in a properly grounded hardwire system is the voltage present in at the very most a 1 watt audio signal from a headphone amp.This voltage will vary from manufacturer to manufacturer based on the amperage of the system, but can be calculated like this: (Watts / Amps = Volts)

The hardwire systems, even the ones that use CAT5e (ethernet) cabling still have voltage that could potentially be looking for a ground if there is a faulted ground in the system. These voltages can be high enough that if they make it down the system to your earpieces, could create a small electric charge that could be released onto your outer ear via the cabling. In most cases this will discharge to you (using you as a conductor) and to the ground harmlessly. However, in very rare occasions this charge may build up if you happen to be ground isolated and may cause your earpieces to become warm or even hot. Again, this is harmless to you, but, over time, this may cause irreversible damage to your earpieces.

If you experience these small shocks, or the heating of the earpieces, you should immediately discontinue use of your earpieces, and look for the faulted ground in the sound system. This could be a lengthy hunt depending on the complexity of the sound system in question. That is because the problem may not be in the monitor system at all. It could be in ANY system that shares AC power or a linked audio line that is not ground or transformer isolated from the monitor system. For example:

Let’s just say that you are in rehearsals at a church. You experience the “Shock” indicated above and start to hunt for the problem. You check all of the power plugs on the monitor system and all of them have a proper ground via a 3 prong Edison wall connection. We then should move on to FOH, where we find a reverb in the FOH effects rack that has a ground lift (cheater) plug on it. This unit, all the way at FOH can be the cause of your issues. This piece of gear is looking for a proper ground, which it can’t find via it’s normal path (the 3rd prong of the Edison outlet). It then allows that voltage that is looking for ground to travel down the shield (pin 1) of the XLR connector of the output that it is sending to the FOH console. That voltage then travels though the ground chain of the console which includes it’s access to pin 1 of the other channels in the snake. The shields of the snake lines carry that voltage back to the stage where it travels into the monitor console and out to the monitor mixes and to your earpieces, thus finding the easiest way to ground…YOU.

This may sound a little far fetched, but this very scenario was discovered by one of our clients when I notified him of why he was having this issue. It took him and the engineer at the church a couple days to find the problem, but once they removed the cheater from the reverb unit, the shocking problem was gone.

So, if you get a shock, and aren’t sure why. Please have a look at your sound system. It could be something as far away as a Video playback system that sends audio to the PA that has a problem. Remember ANYTHING ELECTRICAL that is connected to your sound system can be the culprit.