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Discussion Starter #1 (Edited)
When I plug in my subwoofer with the ground connected, I hear a humm - at volume equal to what I hear in movies. It's quite bad.

My computer has been restarting when I touch the outside of the case, often with a spark, some times even visible.

..So, my brother in law and I re-did the ground wiring in the house, to these outlets. The ground wires were not actually.... connected. They were wrapped around each other a few times, and let go. Then, they came apart.

We wrapped them better and put nuts on them.

...

Now, the issue still exists. I'm in an apartment that has it's own breaker box, which comes off of a box in the house.

The wiring in the house has the negative and ground wires mixed together. I was told this creates the noise I hear on my sub, that's ruining the ground.
I buy this theory, as my my sub issue almost completely disappears when I disconnect ground.

Is that correct?

My thought is to get two new ground rods and run my apartment wiring to them, instead of the ground rod the house uses.

Will this work? Will it work well enough? .. Can I improve further?

I ask, for two reasons:
I was told that mixing negative and ground can put some noise on the negative line, too. Is this true? It may explain why there's a *small* amount of noise from my sub, even with ground off?
And, I'm a PC tech. I have many electronics, and will have customer's PCs in. The electric must be good.

Advice appreciated. Thanks.
 

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retired elect/hvac/plumb
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:eek:
 

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retired elect/hvac/plumb
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Made my head hurt thinking about it! :laughing:
 

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Discussion Starter #5
Mine too. If only you knew how much time I put into diagnosing my PC before learning it was an electrical issue.

Now, I need to get this fixed correctly. Hopefully someone can tell me what to do. :)
 

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retired elect/hvac/plumb
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Are the house and apartment fed from same panel?
If there is only 1 main service panel for both the neutrals and grounds get connected to same buss in panel which is also bonded to the panel itself.
If you have a seperate sub panel for your apartment the neutrals and grounds get landed on seperate buss bars in that panel.
Im not really sure how all this plays into static on your speakers,Ill wait for some techno type to answer that part for ya :)
 

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retired elect/hvac/plumb
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Yes then you have a sub panel,neutrals and grounds should be seperated in that panel then,but like I said I know nothing about speakers :)
 

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Discussion Starter #9
Yes, I believe they are separated in the apartment's panel. They weren't, but I believe my brother in law corrected it.

They are still mixed in the house panel, which feeds these.

Thanks for the replies, mate. Hopefully this helps someone figure it out.

Yes then you have a sub panel,neutrals and grounds should be seperated in that panel then,but like I said I know nothing about speakers :)
 

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retired elect/hvac/plumb
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They dont need to be seperated in the main panel feeding your panel,only in yours :)
 

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retired elect/hvac/plumb
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Yes :)
 

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Let's take a step back and see if we can work out some of the basics:

Now, the issue still exists. I'm in an apartment that has it's own breaker box, which comes off of a box in the house.
1) Is the apartment part of the house, or is it a separate building? Are you the only apartment in the building?
2) How many wires run from the main panel on the house to the sub panel for the apartment? (I'm guessing 4)
3) Does the apartment have its own meter?
4) Is the lot zoned for an apartment, or is this an under the table apartment? (affects whether you are required to bring in a licensed electrician).


The wiring in the house has the negative and ground wires mixed together.
5) Where are the grounds and neutrals tied together?
- At the main service panel for the house?
- At the sub panel for the apartment?
- At outlets and receptacles in the house and/or apartment?
- Elsewhere?

The wiring in the house has the negative and ground wires mixed together. I was told this creates the noise I hear on my sub, that's ruining the ground. I buy this theory, as my my sub issue almost completely disappears when I disconnect ground.

Is that correct?
When the grounds and neutral are tied together, the ground wire will start to carry a voltage. Thus the subwoofer will see less voltage between ground and hot/neutral than it's expecting. I'm not sure what this will due to a sub, but I could see it leading to the humming you mentioned. The voltage on the ground line would also explain the arcing when you touch your computer case.

My thought is to get two new ground rods and run my apartment wiring to them, instead of the ground rod the house uses.

Will this work? Will it work well enough? .. Can I improve further?
Maybe but probably not. The main purpose of the grounding rod is to ensure that the main panel and your connection the power line's neutral are at a lower voltage potential than any other path (such as through you) when a short occurs. Electrical equipment also finds it to be a handy 0 reference.

As for rods required at detached buildings, I'm pretty sure that this is mainly to dissipate any induced current the ground line picks up during the run to the 2nd building.

And, I'm a PC tech. I have many electronics, and will have customer's PCs in. The electric must be good.
Just means you'll get more repeat customers. :jester:

6) Have you tried measuring the following voltages at an outlet in your apartment?
- Hot to Neutral
- Hot to Ground
- Neutral to Ground
 

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Discussion Starter #14
1: Part of the house. Mine is the only apartment.
2: I believe 4.
3: No.
4: Unsure. It wasn't my doing.
5: At the breaker box for the house.
6: No.. I have a DVOM, but it's really hard to make a connection. What should I use?

Let's take a step back and see if we can work out some of the basics:



1) Is the apartment part of the house, or is it a separate building? Are you the only apartment in the building?
2) How many wires run from the main panel on the house to the sub panel for the apartment? (I'm guessing 4)
3) Does the apartment have its own meter?
4) Is the lot zoned for an apartment, or is this an under the table apartment? (affects whether you are required to bring in a licensed electrician).




5) Where are the grounds and neutrals tied together?
- At the main service panel for the house?
- At the sub panel for the apartment?
- At outlets and receptacles in the house and/or apartment?
- Elsewhere?


When the grounds and neutral are tied together, the ground wire will start to carry a voltage. Thus the subwoofer will see less voltage between ground and hot/neutral than it's expecting. I'm not sure what this will due to a sub, but I could see it leading to the humming you mentioned. The voltage on the ground line would also explain the arcing when you touch your computer case.


Maybe but probably not. The main purpose of the grounding rod is to ensure that the main panel and your connection the power line's neutral are at a lower voltage potential than any other path (such as through you) when a short occurs. Electrical equipment also finds it to be a handy 0 reference.

As for rods required at detached buildings, I'm pretty sure that this is mainly to dissipate any induced current the ground line picks up during the run to the 2nd building.


Just means you'll get more repeat customers. :jester:

6) Have you tried measuring the following voltages at an outlet in your apartment?
- Hot to Neutral
- Hot to Ground
- Neutral to Ground
 

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UAW SKILLED TRADES
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You have ground loop noise. Any computer based audio system is subject to this problem. You need to break this loop between devices that provides for alternate paths to ground. I'd start by disconnecting devices and cables and other equipment one by one to determine which one is causing the loop to ground.
 

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Bonding all of the related pieces of equipment to one another usually solves this problem. You may do this by daisy chaining a length of (preferably green or bare 14 gauge) wire from one piece to the next, attaching the wire (you will have to fabricate the attachment means) to the exposed shell of an RCA jack (jack for input or output) or with a screw that penetrates to the metal chassis. Connect the far end of the wire to a known ground, which in some cases can be a radiator or a screw that holds the cover on a power receptacle.

Unplug the equipment during the time you are hitching up this ground wire.

Connecting the far end (splice on additional lengths of wire if needed) to the terminal strip in the breaker panel holding all the white wires (neutral bus) is the best; connecting to the metal panel itself is second best.

You don't need to bond the TV and amplifier and DVD player group in one room to the computer and printer and scanenr group in the next room if there are no audio or video cables going from one group to the other. However when you finish running separate ground wires for each group then the groups will be bonded to each other (no harm) using the rule: if A is bonded to B and B is bonded to C then A is bonded to C.

Sometimes reversing the plug in the receptacle helps. (Applies to two prong plugs both of whose prongs are equal in size.)

You are free to at any time to drive a ground rod (regulation size is 8 feet down and 5/8 inches in diameter) and connect a #6 copper wire from this to the neutral bus in the panel; this is unnecessary if there are already two such rods. Connecting your electronic equipment to a ground rod that is not so bonded to the panel will not solve the problem. (The ground rod with or without bonding to the panel will work fine for shortwave radio reception.)

Walking across a carpet and then touching a piece of equipment can produce a visible spark regardless of how well the equipment is grounded.
 
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