Grounded Plugs: Pulling out the third prong

Mohoyoho

I have been told by a well respected member of this forum that every musician should pull out the ground prong on their AC plugs. At first I felt that wouldn't be right, but as I thought more and more about it, I think he is correct. After all, my Waldorf Q doesn't have one. And then there's all those wall wart adapters that aren't grounded to the outlet. I have a ground lifter on my laptop.

Should I do the same for my mixer?

Is it dangerous not to be grounded? What's everyone's opinion?

kkissinger · Posted: Sat Apr 28, 2007 6:57 pm Post subject:

My opinion is not to disable the ground plug since the ground plug is a safety feature.

To use devices such as the Ebtech Hum Eliminator has worked for me when I've had ground-loop issues.

Mohoyoho · Posted: Sat Apr 28, 2007 7:01 pm Post subject:

What exactly are the safety issues? Are those people who use Nord G2s and Waldorf Qs at risk? I'm confused. You hear about rockers with guitars getting zapped touching a microphone. Can that happen with synths?

kkissinger · Posted: Sat Apr 28, 2007 7:20 pm Post subject:

Well, I'm not an electrical engineer thus I am sufficiently intimidated by the manufacturer's warnings not to cut off the ground plug.

I have been told that the reason for the ground plug is in case a situation develops (a short, perhaps) that inadvertantly diverts line current to a device's case. The current would pass to ground rather than passing through a person who touches a conductive case part.

I heard of a guitarist (years ago) that was electrocuted when reaching for a mike -- however, I have no idea how the equipment was configured or whether a faulty ground was the culprit.

Mohoyoho · Posted: Sat Apr 28, 2007 7:46 pm Post subject:

Certainly high amperage equipment should be grounded: 1200 watt pa amps, DJ lighting, etc. But what about the small aperage stuff like synths? I could see grounding for household appliances like water heaters, stoves, refridgerators. But you never see them for clock radios, CD players, etc. I'm no expert: just curious.

jksuperstar · Posted: Sat Apr 28, 2007 8:09 pm Post subject:

I don't know if the real potential for using ground as a safety feature is truly built in to all devices. Yes, it is there to divert current from the case of the unit to ground. But, if that work as well as it should, we do we now have ground-fault protection devices to stop the current? (BTW - without a ground, the ground-fault protection is useless). But will you ever mix in the rain while standing in a puddle? You're shoes, and the plastic knobs also serve as protection.

by the way, there is less & less gear I own that has a ground. In fact, I have 1 device left (a Lexicon MPX-1) that has the standard IEC 3-prong plug.

Mohoyoho · Posted: Sat Apr 28, 2007 8:53 pm Post subject:

My Mackie mixer, Voyager, and Phatty are the only gear that have 3 prong grounded plugs.

modulator_esp · Posted: Sun Apr 29, 2007 4:35 am Post subject:

Everything I own with an internal power supply has a ground connection

Quite a lot of stuff with an external power supply also has a ground

When the ground worked loose in my Mono/Poly all sorts of weird things happened, noisy outputs, distortion etc

blue hell · Posted: Sun Apr 29, 2007 7:41 am Post subject:

Safety grounding is a safety measure used on equipment where a potential risk is present for externally touchable parts to come into contact with the mains voltage.

Such a problem could occur as a result of a fault in the equipment where a mains wire loosens for some reason and touches some metal part that can be touched by the user as well (this could be the signal ground for instance). The problem can also occur when the device gets wet, like when being on an outdoor stage in the rain.

So it doesn't really matter if it's "power" equipment or not, the criterium actually is that whatever single fault occurs in the equipment the the user should not be connected to the mains voltage. Again a possible fault condition could be water running into the equipment.

Another way to achieve safety is by means of double isolation. Even equipment in a metal housing can be double isolated when special care is used in the construction. For instance my G2 engines use a two prong power connector but they are in a metal housing.

However double isolation will not protect very well in a wet environment and that is why equipment to be used in wet environments usually has a safety ground - sometimes even two.

For closed systems with no external metal parts the safety requirements are pretty easy to implement without applying a safety ground. For audio equipment it's a bit less easy as it is nearly always the case that there are externally touchable metal parts (i.e. the signal ground). When to be used in wet environments I'd appreciate a safety ground to be present, even when such will mean that ground loops are present. for a dry environment I would just ground lift everything, with one possible exception - the PC.

What is often seen on PC power supplies is an input filter on the mains input that effectively connects the case to half the mains voltage. This can lead to unpleasant sensations when touching such a PC and something connected to earth at the same time (like a central heating pipe, f.i.). When that PC is connected to the audio chain as well (through normal audio jacks, non-optical I mean) the whole audio chain will be at half the mains voltage. It is not that a lot of current will flow when you touch it, be it can be enough to feel unpleasant. In such a situation I want a safety ground on that PC.

In modern electrical installations there are devices that can detect fault situations like current flowing where it shouldn't. There are two types of devices for that, the earth leakage current detector and the residual current device (got the names from : http://en.wikipedia.org/wiki/Residual-current_device ).

The first type needs the safety earth to be present as it measures the actual current flowing through that wire (and that should be near zero). The 2nd type however will also work when no safety ground is present as it measures the difference between the current flowing into and out of the appliance - that difference should be near zero. In all modern electrical installations the 2nd type would be used with a possible exception for stuff like washing machines.

So .. is it safe to cut the 3rd wire ? Well it depends Very Happy

In a normal "household" situation like a studio I see no real problem especially not when a modern electrical installation with ground leakage protection is present. For indoor podia I'd reason likewise. On an outdoor stage with possible rain the situation is completely different, I guess I'd refuse to work in such a situation without proper safety grounding. Especially as in that situation there will most probably no external protection installed - it would trip all the time I guess.

Depending on te quality of the actual electical insatllation you could be somewhat more or less careful I guess - in my home I have no earth leakage detection which makes me act more careful (had some nasty shocks in the past).

Sorry for the lengthy reaction, hope it helps.

blue hell · Posted: Sun Apr 29, 2007 7:50 am Post subject:

Oh I forgot about the wall wart stuff ...

It is beyond me why a laptop would need to have a safety ground connected through the power supply to the laptop's signal ground. I can imagine that it would be OK to have protection on the power supply itself, but there should be no need to connect it through to the laptop.

The same holds for my Behringer mixer with external power supply.

Stuff like this is nearly useless IMO for protection and it always adds a ground loop which especially for the laptop is nearly always troublsome as well.

I power lift such devices, and would not operate those in a wet enveronment (as apparently the power supplies used are not safe for such situations, otherwise the protective ground would not be needed at all).

Mohoyoho · Posted: Sun Apr 29, 2007 8:06 am Post subject:

Jan, thanks for your explanations.

Let's say one is on a stage where there is a ground loop problem. If all your equipt. is going into one outlet and you were using a multi outlet power strip, could you merely lift the ground at the power strip; that is, put a ground lifter on the strip's plug and then into the wall outlet?

blue hell · Posted: Sun Apr 29, 2007 8:17 am Post subject:

elektro80 · Posted: Mon Apr 30, 2007 4:44 am Post subject:

elektro80 · Posted: Mon Apr 30, 2007 5:05 am Post subject:

elektro80 · Posted: Mon Apr 30, 2007 6:21 am Post subject:

As for DI boxes, this is a huge field. Basically there are passive and active designs, but what they atually do can vary a bit. It is always smart to have several types in the gear closet, but active ones with a good line driver with a switch for several output levels is a good first choice.

Kassen · Posted: Mon Apr 30, 2007 8:03 am Post subject:

elektro80 · Posted: Mon Apr 30, 2007 8:13 am Post subject:

Agreed.
Also: Keep in mind that there are certain shielding/grounding issues internally in a laptop that does not have anything to do with the audio path.

The absolute best way to handle laptop audio is to use pro/semipro audio interfaces and a balanced audio path. Use DI/active line drivers when connecting non balanced gear to the laptop.