# Ground Loops



## Andre (Feb 15, 2010)

Well I have found that I have a ground loop problem coming from my coax cable. I have tried to ground the coax at the point it enters the home but that didn't work.

I have been searching the internet for a CATV Isolator but I haven't been able to find one that is over 1ghz and I take it from reading that my HDTV would need one that is at least 1.5ghz, now that could be wrong but I is what I have read.

As for a RCA ground loop isolator (to go between the receiver and the amp for the main speakers) there are tons of those but most on Amazon "look" pretty chintzy, and a lot of the reviews are saying they rob bass.

I have looked into a DI box but all I have found are unbalanced to balanced and they are quite expensive

So I am ask for opinions, and "where to buy" (In Canada if possible) for the best quality isolator I can get to get rid of this 60hz hum

tks


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## Wayne A. Pflughaupt (Apr 13, 2006)

Andre said:


> Well I have found that I have a ground loop problem coming from my coax cable. I have tried to ground the coax at the point it enters the home but that didn't work.


It needs to be grounded to the same copper stake as the house electrical service.

P.S. Welcome to the Forum!

Regards, 
Wayne


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## Andre (Feb 15, 2010)

It is grounded to the same copper wire as the main electrical panel. I am wondering if twisted pair rca between the demon 4000 and the crown amp might work


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## Wayne A. Pflughaupt (Apr 13, 2006)

Andre said:


> It is grounded to the same copper wire as the main electrical panel.


Are you saying that there is no ground stake for the service?




> I am wondering if twisted pair rca between the demon 4000 and the crown amp might work


That’s a substitute for shielded wire, and as such only addresses EMI. Ground loops are not an EMI issue.

You might want to wade through the BFD Hum Thread...

Regards, 
Wayne


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## Andre (Feb 15, 2010)

If there is a Ground stake I have never seen it, perhaps they use something else in Canada. Still the copper line coming into the houses electrical panel IS the same ground that is being used by the CATV coax so by rights there shouldn't be a ground loop problem with the cable, however after unplugging ever component one by one, disconnecting the coax was the only thing that brought the noise down to almost nil


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## istvan (Jul 5, 2013)

I see you were thinking of isolating the audio. Why not get a coax isolator ? http://www.amazon.ca/TII-Ground-Loo...d=1429788299&sr=8-13&keywords=ground+isolator


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## dhrab (Nov 3, 2013)

Just a long shot here ... if the CATV ground is bonded to the same ground as the house’s main ground as you’ve mentioned ... your problem maybe you are plugging some of your equipment into a circuit whose breaker is on the opposite side/phase in the main panel box 

Most rooms are split with one phase on one leg in the main panel box and the other side of the room’s outlets are connected to the other phase in the main panel box ... I believe this is done to balance the household loads evenly in the main panel box and has nothing to do with audio ... it’s about balancing the load in the room 

Unfortunately if most of your equipment is plugged into an outlet (dedicated or not) that has it’s breaker on the “A” phase of the main panel box and you stick your subwoofer in the corner ... the subwoofer circuit maybe on the opposite side of the room and that circuit may terminate on the opposite side of the main panel or the “B” phase

This is an instant ground loop condition as there is a difference in ground potentials due to the different lengths of the ground wires that lead to the main panel box .. because of the different lengths of the ground wires a oscillation between the two ground wires of different lengths occurs and appears as a HUM at our speakers 

Try this ... get a power strip capable of handling all the power leads/cords from all your equipment and plug all your equipment into that strip only ... then plug that power strip into the wall and see if the HUM goes away ... by doing this with all your equipment plugged into the one power strip ... when you plug the power strip into the wall outlet you will only be on one phase in the main panel box and hopefully the HUMMING will subside

Like I said just a long shot


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## Andre (Feb 15, 2010)

I have tried unplugging individual pieces of the component chain to find the "culprit", and that didn't seem to lessen the hum.

Another note that has occured to me is that I didn't have the problem prior to purchasing the Crown XLI pro amp to power the Axiom M100s. It is attached to the Denon X4000 via the pre amp outputs.

When I disconnect the CATV cable the hum goes away. Also when I disconnect the RCAs from the Denon to the Crown.

Previously I mentioned a concern when the CATV insolators on Amazon thinking they may not be "efficient" enough to handle 1080i, but perhaps I am wrong.

Looking at unbalanced Isolation blocks you find cheap filters such as this

http://www.amazon.ca/Audio-B25N-Gro...F8&qid=1429797195&sr=8-6&keywords=ground+loop

To something like this

http://www.avshop.ca/sound-amp-pa-a...controllers/art-dti-dual-transformer-isolator

There are also "galvanic" isolators but I take it these are for Marine applications


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## jbc (Apr 22, 2015)

I had exactly the same problem recently - a hum caused by the coax cable - and solved the issue with a Jensen video isolator (VRD-1FF). I can vouch for its effectiveness, and for its compatibility with a (Shaw) PVR cable box - no issues with channel dropouts or menu/guide. 

Being in Canada, I had to mail order from the states, so there's a bit of shipping to pay. While it may have been possible to get away with a cheaper capacitive isolator, the Jensen one is specced at 2-1300MHz, so I went with it and it worked.

At the same time, I'm going to have the cable company look at the cables coming into my house, as I suspect there may well be some degradation of the shield.

Hope that's useful,
JBC


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## TomFord (Jul 15, 2014)

After I upgraded my subwoofer I had a significantly large ground loop. The hum was very loud, and quite awkward thinking back on it. Thought I was going to have to return the subwoofer for the lesser Polk Audio that it replaced. Thankfully, a few minutes of research led me to this isolator by Viewsonics 

http://www.amazon.com/Viewsonics-VSIS-EU-Cable-Ground-Isolator/dp/B0017I3K9M

I was considering the isolator made by Jensen that was over twice the cost at $50 if memory serves, but have always disliked the brand. When I hear Jensen I cringe a little involuntarily. Believe it's due to seeing car audio systems with the J word "2000" watt amps that in reality put out 200.

For $20 I was able to get rid of the loop entirely. My other speakers sounded slightly cleaner, albeit barely noticeable, and I hadn't noticed a hum from them at all at any volume level. I placed the isolator between the cable from my provider coming out the wall in between the DVR. 5 minutes. Most simple, less costly repair/improvement so far.

Highly recommend to anyone with 3 or more components. e.g. AVR, DVR or cable box, and DVD player or PS4/Xbox
Recommended to a member a few months back and it resolved the issues he was having as well. 

Let us know how it works out


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## jbc (Apr 22, 2015)

I think Jensen Transformers and Jensen mobile (makers of auto/marine amps and speakers) are two separate companies, correct?


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## TomFord (Jul 15, 2014)

jbc said:


> I think Jensen Transformers and Jensen mobile (makers of auto/marine amps and speakers) are two separate companies, correct?


Correct. You had me google it. The Jensen (cringe) mobile site showed the speaker series called "Dub". Ha. I can't.. it's just too much to take. 

Plus the Viewsonics was less than half the cost and, similar specs with a larger frequency range covered. If it didn't work could send it back with Amazon. Rarely do, yet when I return something there's no


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## Andre (Feb 15, 2010)

Well the Jesen TriAx 6X9 speakers were the "Coolest" back in the 70s, everyone wanted them...

I have ordered this item to see if it will work, if not I will try the Viewsonics

http://www.amazon.ca/Link-NF103-Ref...=UTF8&qid=1429911747&sr=8-19&keywords=db+link


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