Proper Ground for Computer and speakers, is it really un-safe or is it all hype?

Aloha all,

Before you jump all over me and tell me its unsafe, take a listen.....

Everything in my office is connected to 2 different 1500 WATT UPS (with proper ground)


In my office i have powered studio monitors (mackie) . These speakers have a standard PSU power cable 3 prong. When connected into my UPS, they buzz, very light buzz but you can hear it. When you switch the cords (with cut off ground) the buzz is gone, cant even tell if they are on.

Why is this unsafe or it is safe because Its not directly plunged into the AC outlet?

I am not an electrician, but using normal judgment I feel its safe because of if there was a power spike or my house got hit by lighting it would stop at the UPS....

The Computer is grounded, just un-grounded the Studio monitors....

Again, why is this unsafe or is it all hype?

I also wanted to say that I have a my speakers connected to a Monster Home Theatre Reference Power Center HTS3600

http://www.monstercable.com/productdisplay.asp?pin=3259

I have everything i need to make the line clean, and it still buzzes.. for a year i though it was because of the computer (RCA) , however using a ungrounded power cord, problem gone..

I spent a ton of money on the monster power thing that didnt help at all.....

I know the problem is with the electric in the house, but really, how do you fix that ?

I agree with all of this, but however everything I have is connected to the Power Center and that has a proper ground.

Most likely, the outlet you have the equipment plugged into is not a dedicated ground isolated outlet, and the noise your hearing is from other equipment plugged into the same circuit radiating through the ground line, or from having each equipment on different circuits (PC is on one circuit, your speakers are on a different circuit).

Sensitive electronics should have a dedicated outlet with the ground wire of a 2 wire cable (Hot, Neutral & Ground) wired with the ground wire only to the ground of the outlet and directly to the ground bus bar in the circuit breaker panel and nothing else in between. And all interconnected equipment should be on a single circuit to prevent any ground faults/loops.

The ground is mainly used to protect people from possible faults in the circuit, such as the Hot wire making contact with a appliance case. Without the ground, the case would be energized and anyone who touches the case, would get electrocuted because they would complete the circuit. With the case grounded, if the Hot wire made contact with the case, it would complete the circuit and flow to ground instead, and trip the circuit breaker.

Mpegger said:

The ground is mainly used to protect people from possible faults in the circuit, such as the Hot wire making contact with a appliance case. Without the ground, the case would be energized and anyone who touches the case, would get electrocuted because they would complete the circuit. With the case grounded, if the Hot wire made contact with the case, it would complete the circuit and flow to ground instead, and trip the circuit breaker.

Click to expand...

That's it alright.

If everything works correctly it's safe to be ungrounded, but if something fails even a little bit it is very, very dangerous.
Do not run without a ground.

how are you connecting the speakers?
if you have a ground loop type occurance, why not use a ground loop isolator? they are $15 at your local radio shack. for analog stereo connection type stuff.

for digital a simple optical isolation should fix the issues?

or is it ONLY because your connected to the UPS and some modified sine wave stuff (or some such issue) is inducing noise into them?

i woundt call it unsafe, been shocked many times from doing Stupid stuff with AC depends, are there any other humans there you can kill with it , liability and neglagence can be a bigger pain than an AC shock
yes i have been frazzled , tingled, and blasted by mixes of power connections and improper grounding, but i am still alive and kicking even after getting the back of a CRT discharged into me. yup can happen , it is there for a reason. What would kill me is spending 2-4 years in Court , for an incident that i cause to another human.

also try the exact same "resistance" between the AC connected devices , that will keep a voltage differential from existing between the devices. AKA try the exact same length and type of extention cord , even if you have to move the UPS to the middle between the 2 items. (which also would mean test without the monster thing)

.

I'd suppliment Psycogeec's "How are you connecting the Mackie's" with "Are you using balanced XLR or TRS inputs on them, or unbalanced RCA's"

If you are using balanced conections from a "Pro" soundcard or DAC, then it is safer to lift the shield (pin 1 on XLR or the "Sleeve" on a 1/4" TRS) as this will also break the ground loop while keeping the AC Mains ground intact for safety.

I'd probably avoid cheap isolation transformers in an unbalanced scenario as they will color the sound (good isolation transformers that are on-par with your $,$$$ monitors are not cheap)

Do the speakers buzz w/o the inputs connected? And are these the HR series or the MR series?

They are the Mackie MR8's I have three of them. I have balanced XLR going to them. With the XLR un-plugged, they still buzz. Its very light buzz, but its there.. If you un-ground them, then no more buzz at all, you cant even tell they are on.

The mackie's are connected to the Moster Cable Power station witch is made to help prevent noise and stuff....

What if you bypass the Monster thingy? If the speakers themselves are humming w/o any inputs connected - that tells me the Monster Conditioner is noisy (a real possibility), your AC Mains are just that contaminated (just your ground apparently) or your MR8's are defective or simply noisy "as-is" (but the fact that lifting the ground silences them rules that out)

I know my "Old School" HR824's and HR626 (USA Versions) actually use 2-prong IEC AC Power connectors (no ground on any of them) - where as my Dynaudio AIR-15's and AIR-BASE-2's al have the 3rd ground pin (and are completely silent).

I'm sure the HR824's and 626's were "Designed" to work w/o a true ground - so maybe your MR8's would be alright w/o one?

Proceed with caution like Psycogeec mentioned as evenrything can be 100% fine - but if the amps short out and you touch the rear panel you could be in for a nasty jolt!

You have a ground loop problem. This usually happens when the electrical potential at the grounds of various audio components are different. You can get isolation transformers that will help, however if the Mackies are buzzing even with nothing connected I would try jacking them directly into the wall outlet. UPS's aren't designed with powered pro audio monitors in mind anyway.

Lifting the ground via pulling the ground pin works, as you have discovered, but it's not really the safest thing in the world (says the guy running an 1800W QSC pro amp in the home theater with a lifted ground).

But he gets the HUM even w/o any INPUTS connected to the speakers! (Just the grounded AC power - no chance of a "Loop" w/o an input connected ). Yanking the AC Ground eliminates the hum. Something is fishy with the AC Ground (likely VERY contaminated with noise, etc).

ya see what i mean The hum goes away if i use a different plug in the house, but we talking moving it to the other end of the house to correct the problem...

It could be as simple as a loose or oxidized ground connection on that outlet or at the breaker box (be VERY CAREFUL if you go poking around your junction box for a loose ground bus bar connection!!!), or it could simply be other induced noise on that same circuit. What else shares that "noisy" circuit with that particular outlet (what else turns off if you flip the breaker that feeds that outlet)?

And did removing the Monster Conditioner from the equation increase or decrese the ground noise on the noisy circuit?

It's fairly odd that you're expereincing this, but I have heard of weird things like this even when ground loops aren't a contributing factor (as in: having your inputs un-hooked but still getting the noise from the AC Ground).

Wizzard005 said:

ya see what i mean The hum goes away if i use a different plug in the house, but we talking moving it to the other end of the house to correct the problem...

Click to expand...

It is slightly possible that the PLUG that your plugging into might be wired incorrectally.
if another plug item at the same location doesnt have the issue, and OTHER items that are on those same curcuits are turned off to test that theory. But then mabey that curcuit also runs the refrigerator or something?

if the plug is not wired proper, and your testing shows (tiny) AC going across the ground inproperly, then you gotta wonder what is happening in other devices that just dont "say" anything about what is happening
.