I am going to be building a new home, in the spring. In my current theater, I have dedicated 20 amps lines. However, I still had ground loops as they did not share a common ground. For my new theater, I was thinking a using something like this http://www.exactpower.com/products/pcore/pcore.aspx . Comments?

You'd be better-off contacting Ground-One (Arthur Kelm) at the design phase of your home and have him spec a proper grounding system for the home- you'll see that it's worthwhile, much cheaper than a product like that, and probably all that's really necessary.

www.ground1.com

trust me, he's the man when it comes to power and grounding.

Dan

Wow, you'd think the guy with his credentials would have a better website than that!

I agree with Dan though, what exactpower doesn't mention is if you introduce a satellite or cablevision line that's grounded out at the telephone pole rather than in the house (almost all are a free floating line from the pole to the house), then your ground buzz will return, regardless of the size of isolation transformer installed on the AC side of things.

The system needs to be designed right, and right now you've got a clean sheet of paper. (I'm jealous!)

didnt have the same ground? do you have two completely independent load centers? not that it is not possible but highly uncommon.

Ground loops can be caused by having the current on two different legs. A real easy fix for this is to just change the position of one of the circuit breakers.

So how do you know if they are on the same leg? Assuming that you have a standard single phase 220~240v residential service, if the 2 circuit breakers are right next to each other either vertically or horizontally then they are on opposite legs. Move one breaker so that it is adjacent vertically or skip a breaker horizontally.

if they are apart from each other count the spaces, in the same column they should have an even number of spaces, if it is in the other column they should have an odd number between them.

If they are in 2 separate boxes have them rewired if you cant handle it yourself following the above guide lines.

Basically you want to address this from the source and not try to cover it up afterwards (power core).

Also are you sure that the hum is coming from the power source? Since you have an existing system in place, I would do some basic troubleshooting to see if i could eliminate the problem before even starting a new design.

First read:

"The TRUTH" from ExactPower of Middle Atlantic Products
http://www.exactpower.com/elite/wpapers.aspx

or a long version of the same paper

"Power White Paper" from Middle Atlantic.com
http://www.middleatlantic.com/power.htm

Have you tried just connecting the system to one outlet? I don't know your setup but I dont see why you couldnt connect the whole system on one line to check. just wait like 20sec between turning the amps.

A 20 amp line should accommodate your system at a low level

If I were to build a new room. I would use a over-sized 3 wire plus ground 240 volt run to a 6 (or less) breaker sub-panel as near to the A/V equipment location as possible. I would put half the big audio amplifiers on one phase and the remainder on the other phase. This will reduce the AC voltage drop to the amplifiers and more importantly reduce the AC neutral current. Everything will be on a common neutral and a common safety ground. which have a large impact on ground-loop reduction.

You'd be better-off contacting Ground-One (Arthur Kelm) at the design phase of your home and have him spec a proper grounding system for the home- you'll see that it's worthwhile, much cheaper than a product like that, and probably all that's really necessary.

www.ground1.com (http://www.ground1.com)

trust me, he's the man when it comes to power and grounding.

Dan

Great advise!!!@@@

So how do you know if they are on the same leg? Assuming that you have a standard single phase 220~240v residential service, if the 2 circuit breakers are right next to each other either vertically or horizontally then they are on opposite legs. Move one breaker so that it is adjacent vertically or skip a breaker horizontally.

if they are apart from each other count the spaces, in the same column they should have an even number of spaces, if it is in the other column they should have an odd number between them.Actually, with most (all?) modern 120/240V residential load centers, breakers directly across from each other (same row, different columns) share the same tab, so they are on the same leg. The adjacent slot above or below is the opposite leg. To have several circuits on the same leg you want them in the same row, or with an odd number of rows between them no matter which column they are in.

The slots are arranged inside the panel with legs "A" and "B" like this:

A - A
B - B
A - A
B - B
etc.

If you have a local Lowes or Home Depot and look at the displays in the electrical department, you can see how the two bus connections are arranged.

What gets more confusing is that sometimes "tandem" breakers are installed - these are two half-width breakers in a single unit that takes a single slot. If you have these, you want to count slots, not handles.

Just grab a voltmeter and measure between breaker outputs. 0 volts = same phase. 220 volts = not on the same phase. :)

You'd be better-off contacting Ground-One (Arthur Kelm) at the design phase of your home and have him spec a proper grounding system for the home- you'll see that it's worthwhile, much cheaper than a product like that, and probably all that's really necessary.

www.ground1.com

trust me, he's the man when it comes to power and grounding.

Dan

Thanks Dan. I will contact him.

Have you tried just connecting the system to one outlet? I don't know your setup but I dont see why you couldnt connect the whole system on one line to check. just wait like 20sec between turning the amps.

A 20 amp line should accommodate your system at a low level
Do not remember the things I tried. No longer concerned about things in my current home other than selling it. I used Hum-X products with great success in my present home. It was a cheap and safe solution that worked well. Clean slate here, so I am going to do it right the first time.

Ground loops can be caused by having the current on two different legs. A real easy fix for this is to just change the position of one of the circuit breakers.


Sorry but that's AVS folklore. The phase of the AC has nothing to do with ground loops. I have been designing television broadcast, mastering and lately DI theater facilities for over 25 years. In commercial environments we have three phase power, and we never worry about which phase we are using. In fact we re-distribute the phase assignments for the sole purpose of balancing the load, not for hum and noise issues. We do practice standard good engineering parctices to avoid ground loops.

The reason so many HT system users believe the "same phase" idea is they often move an offending conponent to the same phase the hum goes away. But the phase was not the problem. Moving to a different circuit broke a ground loop and that's really what fixed the problem.

Mr. Art Kelm at Ground1 definitely understands the problems with AC power wiring. His work is a little pricey for individuals though. A better link to his main site:

www.ground1.com/news.htm