Ground Loop

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Ground Loop

Post by damon » Fri Dec 19, 2008 11:27 am

My LightStar Ref. 1 is currently in a config where I am having to fight a ground loop.

I have a new loadcenter with 20 Amp breakers, wiring & outlets where appropriate for Audio.

Plugged my Amp into a PS Audio 20 Amp Ultimate Outlet & immediately heard a hum. Amp btw, is being fed by a fairly long run which is unbalanced from my Arcam AV-8 Pre-Pro.

Took the Ultimate Outlet out of the equation & things got better but not tolerable. I am now trying an Ebtech Hum-X & things are much quieter but it very plainly states that it is for 15 Amp circuits. I guess I want to know all that I am having to give up with this in the electrical path from a performance perspective.

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Re: Ground Loop

Post by OBI56 » Fri Dec 19, 2008 1:13 pm

Anything much over 5 or 6 feet should be run with balanced cables to avoid hum pickup wherever possible. One other idea out of left field here, but I had a similar problem in my setup. Check that the outlet for your amp is in the same side of the electrical panel as the rest of your system. I had my new dedicated outlet wired with metal wrapped electrical wire to the same side of the panel as my existing outlets and now I don't have any more hum problems. I mentionned this to my locl McIntosh dealer who had a similar problem and he had his listenng rooms rewired at the panel by putting all the outlets in any 1 room to the same side of the panel and no more hum either.
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Re: Ground Loop

Post by TNRabbit » Sat Dec 20, 2008 12:23 am

Do you have any rheostat controlled lights or ceiling fans in the area? They are TERRIBLE for inducing hum.
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Re: Ground Loop

Post by OBI56 » Sat Dec 20, 2008 12:33 am

Correct TNRabbit, Dimmers are horrible for hum. I also just remembered another common source of hum; is by any change your TV or cable box hooked up to your stereo system (maybe through another common compenent)? Cable hookups are notorious for inducing ground loops and hum into systems as most of them are not even properly grounded. By searching you should find several references to ground busting devices made specifically for cable hookups.
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Re: Ground Loop

Post by gdb » Sat Dec 20, 2008 1:02 am

OBI, do you really mean "same side" of service panel or same leg ?? Both legs are accessible from either "side" or vertical row, as in a 230v. breaker taking hold of both "legs" to create 230v from 2-115v sources. :? Geoff

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Re: Ground Loop

Post by OBI56 » Sat Dec 20, 2008 1:42 am

Don't know all the technicals GDB, just what my electrician told me. All circuits for the audio system are on the left side of my panel (breakers) and the HT circuits are on the right side now and that solved my last hum problems.
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Re: Ground Loop

Post by gdb » Sat Dec 20, 2008 2:01 am

Any port in a storm I always say! Glad it's working out OK. I've always been a proponent of using BX or MC cable because its got a built in shielding advantage!(is metal wrapped what Canucks call it ?)Geoff

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Re: Ground Loop

Post by PDR » Sat Dec 20, 2008 10:45 am

we also call it bx

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Re: Ground Loop

Post by OBI56 » Sat Dec 20, 2008 3:48 pm

Yes it is called BX (had a mind fart as I always confuse the term with Romex and Loomex and didn't want ot call it by the wrong name)
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Re: Ground Loop

Post by Jag_97470 » Sat Dec 20, 2008 11:55 pm

OBI56 wrote:Yes it is called BX (had a mind fart as I always confuse the term with Romex and Loomex and didn't want ot call it by the wrong name)
Hey OBI, can you supply a linky for the BX? Just curious, thanks!

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Re: Ground Loop

Post by PDR » Sun Dec 21, 2008 12:29 am

Jag,

You can get bx at almost any boxstore. home depot etc. There are a few considerations using it, like how to
cut and peel back.There are little plastic isolation inserts that you place between the jacket and wires as to
not pierce the insulation on thge wires.There are electricians on the forum that can give you more info.

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Re: Ground Loop

Post by Rainman » Sun Dec 21, 2008 1:12 am

One simple thing you can check is to make sure that every connection is good and tight in your service panel. Before I did the dedicated circuit thing I had a hum in some of my stuff at home that was driving me nuts. A friend came over and fixed it by simply tightening every single thing in my service panel.... Just something to try...

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Re: Ground Loop

Post by OBI56 » Sun Dec 21, 2008 1:40 am

Rainman wrote:One simple thing you can check is to make sure that every connection is good and tight in your service panel. Before I did the dedicated circuit thing I had a hum in some of my stuff at home that was driving me nuts. A friend came over and fixed it by simply tightening every single thing in my service panel.... Just something to try...

Rainman
Good point Rainman. The only reason I went the BX route for my dedicated amplifier circuit was that I had become totally anal about getting rid of the hum and that it only cost me about $20 more than standard electrical cable of the same gauge to have it installed by my electrician. I needed a separate circuit for the amp (Sunfire 300X2) because they wired these houses with so many electrical outlets on so few circuit breakers (I think there are like 30+ outlets on 5 circuit breakers for all the elctrical plugs in the house and luckily the lighting is all on 4 separate circuit breakers for the 3 floors)
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Re: Ground Loop

Post by Rainman » Sun Dec 21, 2008 2:46 am

OBI, I must admit that anytime you are fortunate enough to have friends that went to M.I.T. you are going to benefit from it for sure. I can also say that my going to Motorola school didn't hurt me either.
The noise in my home was actually bad enough that you could actually hear it in the light switch located at the top of my stairs! I was surprised as well as thankful when it turned out to be as simple as a loose ground in my service panel!
One other thing that you touched on was interconnect routing.. Another simple thing that certainly can't hurt is taking the time to make sure that your interconnects are separated from all of your power cables and speaker cables. Try to run them as far away from the other cables as possible. This can be a little frustrating and time consuming, but it doesn't cost you any money to do except for some zip ties etc. It's also just one more thing you can do to eliminate a potential problem......

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Re: Ground Loop

Post by damon » Sun Dec 21, 2008 3:56 am

My HT is in a seperate structure from the house so it is relatively easy for me to expand breakers/circuits in my Cutler Hammer CH4200BR Load Center.

Who here feeds there LightStar with seperate circuits for Right & Left?

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