Suncoast Audiophile Society Message Board Main discussion area (visible to non-members) › Ground loops, cable isolation, and dedicated lines

Ground loops, cable isolation, and dedicated lines

Alan N
user 13931748
Group Organizer
Tampa, FL
Post #: 73
I spent a couple hours today trying to clean up my birds nest of cables, which has been growing exponentially over the past couple years. Unfortunately, I've been dealing with a major ground loop issue ever since upgrading to my C-J preamp and amp, along with the addition of my Oppo universal player, and a bunch of networked A/V gear. I had eliminated some of the hum using three cheater plugs, but felt I should do more to try and isolate the source of the problem. Towards that end, I cut holes today in the sides of my "acoustic bookshelves" (see arrrow in pic), and routed all A/V cables through the (normally hidden) "bass trap" section away from adjacent power cords and ethernet cables below.



Lo and behold, that eliminated >50% of the hum, and adding a single cheater plug (on my amp) eliminated the rest. Next, I'm going to have an electrician add a 2nd hospital grade outlet to my dedicated 20A line, so I can get my HDTV, Verizon box, and ethernet switch off the 15A line. Hopefully, having everything on a single dedicated line (with a common ground potential) will eliminate the residual ground loop entirely.

I'm curious if anybody else has run into major noise/ground loop issues with the advent of merged A/V systems, network connected gear, plus the resulting birds nest of cables?

Bart A.
user 13951957
Tampa, FL
Post #: 3
Hi Alan,

I've had an issue with my living room. One furniture arrangement has always sounded better, even though the other arrangement really should have. This had to do with distance the speakers could be off the wall, distance off the rear wall for seating and the shape of the room. Due to the prime seating area being in a bass mode, I gave up. With these new dipoles, I had read that they did not excite the bass modes as much, so tried again and that was true, but the clarity was still not as good. After eliminating all other possibles, and moving room acoustic treatments all over, the last test was the power. Different house circuits. Jim M. let be borrow some electrical conditioning gear. That instantly cleaned it up. Now, I have to decide which way do go - decisions, decision, and more decisions!

It is an interesting journey & really glad I'm not doing this alone.

Bart
Philip R.
inline_phil
Brooksville, FL
Post #: 2
Hi Alan,
GLs start with miswired primary transformers and end with internal fauxpas.
I have a simple tool that easily determines chassis current leakage and power plug polarity. I am in Tennessee at the moment but when I return I will ring you up and help you out. Plug polarity can fix some issues but with multiple transformers it gets a bit more complicated. The good news is that this problem can usually be easily fixed.
Phil
Alan N
user 13931748
Group Organizer
Tampa, FL
Post #: 75
In my situation, I'm probably dealing with TWO (or more) issues. Firstly, a classic ground loop hum, and secondly, stray RFI from either a) my Sprint Airwave (femtocell) which sits adjacent to my A/V gear, and b) the network switch (connecting my Squeezebox Touch, Oppo player, and Denon surround receiver). I'll relocate the Airwave as the next "experiment". My Verizon Fios coax cable might also be a contributing factor.

I appreciate your offer of assistance, and may very well take you up on it!

Maybe we should discuss ground loops, RFI, and other electrical gremlins as the "theme" at one of our meetings!
Philip R.
inline_phil
Brooksville, FL
Post #: 3
Yes. Maybe even a meeting with a demonstration
Mike K
user 14121317
Tampa, FL
Post #: 31
Alan,

In my many years of Home Theater ezperience, the ground loop hum has almost always been caused by the cable box. And...it ususally winds up coming from the subwoofer.

In the analog cable days we used to make a simple device from parts that cost less than 8 bucks at Radio Shack. But the advent of digital cable made those devices useless.

I would recommend plugging everything back in as it was, and then removing the cable coming into the cablebox...not the electrical, the cable signal carrier.

I bet you that is where your issue is. Verizon can re-ground their line and correct it for you.

Mike
Alan N
user 13931748
Group Organizer
Tampa, FL
Post #: 77
Mike,

I actually did disconnect my Verizon coax when this problem first appeared, to no avail. When I have a free weekend, I'll systematically disconnect everything one step at a time again. However, I'll probably wait until I get the electrician out for the additional 20A line, since I don't want to pull out my center A/V cabinet twice for wall/wire access.

Fortunately, the single cheater on my amp is sufficient for the time being.
Mike K
user 14121317
Tampa, FL
Post #: 32
Alan, A thought. Maybe something....maybe nothing.

I believe you mentioned to me that you run your squeezebox with a hard wired connection.

That is another way the Verizon ground can get into your system. Also if you have run a hard wired connection to the new Oppo....

Hope you find the culprit! smile
Roy L.
user 14502888
Winter Haven, FL
Post #: 1
I have had similar issues many times in the past with several of my systems. 1 cheater plug on amp or pre/amp usually does the trick, however I have had some systems that required 3 or more cheater plugs to work. I have always had problems with ground loops with Quicksilver equipment. I had a tangle of wires and sometimes rerouting them helped. I also had a 20 amp dedicated line installed by my brother in the mid 80's. This was necessary for the Krell KSA 80 I had just purchased. It drew 8 amps at idle. I feel there is no improvement in ground loop issues with a dedicated line vs. non dedicated line. It's just that some combinations are more susceptible.

Also, unshielded cables don't help the situation. I also noticed that when cable is introduced into a system it creates problems. I had one system combined together (A/V HT snd stereo system) anytime I wanted to listen to the stereo system I had to disconnect the cable from the cable box which eliminated the ground loop. When I finished listening and wanted to watch a movie or cable I reattached the cable to the cable box.
Mike K
user 14121317
Tampa, FL
Post #: 35
Roy, exactly.

The cable companies do not ground their lines properly and they will often cause this issue. If you hound them enough they will send a guy out, drive a stake in the ground and hook their ground to it, instead of grounding off to the plumbing or even not at all.

Cheaters will work, and I have used them myself...but they are not really safe for long term use. (been shocked a few times)

Mike
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Tampa, FL

Founded Feb 3, 2011

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