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I have what is most likely called a "ground loop hum", according to a friend I recently spoke with. I was able to isolate where it is coming from,but I do not know how o get rid of it. It is coming from a 20" long Canary star quad cable that is balanced on both ends, with one end being XLR and the other TRS. The TRS side plugs into my mixer. When I unplug them the hum disappears. I am able to send an optical signal (no surprise) to the pre/pro (Sunfire TGP-5) and it plays with no hum.
How do I get rid of this? Do I have to buy a ground loop hum eliminator or is it possible to build one? I am pretty good with soldering, etc. Is there some other way to get rid of it?
Follow Ups:
This thing does wonders if you're really stumped:
http://www.google.com/products/catalog?sugexp=chrome,mod%3D5&q=hum+x&um=1&ie=UTF-8&tbm=shop&cid=4150831127070188071&sa=X&ei=cvfbT_eoNueS6gGl0_mfCw&ved=0CLwBEPMCMAA
Does your mixer have a three prong AC plug?
If so, try a three to 2 prong AC plug adapter temporarily as a test. If the hum goes away then you definitely have a ground loop caused hum. Keep in mind bypassing the ground on your mixer is not something you should do permanently, but it makes for a good test.
Thanks for the suggestion. I did try that and it did not make any difference. In addition the mixer has a ground reversal switch. That does not help either. I also plugged the Sunfire directly into my Tripplite voltage regulator/surge suppressor with no help. The Sunfire has a two prong plug with one wider so that it is inserted correctly. As I write this, I wonder if that is the original plug, as I am the second owner I am going to check that out and I will report back. Thanks again!!
What is plugged in to the mixer???
Afterwards we discovered faith; it's all you need
Dawnrazor - The following are plugged into the mixer: Line out #1 from the Impact Twin to line in #1 on the mixer; cassette deck to line in #2; and CD player to line in #4.
A master out is plugged into the Impact Twin, which is defeated on the front panel so that the turntable is active on line #1 on the front panel.
Thanks!
Do you have any TV/cablebox/tuner etc device plugged into your cable TV coax? The cable company often uses their own ground which can create a ground potential between your house ground and your AV equipment.
If so, as a test disconnect your setup from anything connected to your cable TV coax.
dumpingground - Can you please tell me what you mean by the cable company uses it own ground? Is there someway we can change that or modify it? I have been talking to a cable tech who is a friend of mine. I might be able to get them to solve it if I can point to the problem more specifically.
Thanks!!
see this picture:
http://www.hdtvprimer.com/ANTENNAS/grounding.gif
note that in that picture the coax and the home AC breaker box are all on the same ground.
If for some reason your coax is not grounded near your home then it is referencing someother ground in the CABLETV system which will be different from your home ground.
Note that rather than a ground rod, often your home will be tied to a water pipe which hopefully at some point hits an earth ground and is not a plastic pipe.
Just one more question should clarify this. Is it the fact that the cable uses a different ground or the same ground that causes the problem? My guess is that it is different that causes the ground loop. Hey, I've got a 50-50 chance. :) - thanks again!
different ground potentials caused by grounding to different places is the cause of the problem.
Ideally everything electrical in your system should have the same ground point of reference.
Most cable systems use their own ground ( usually a rod driven in the ground next to the cable entrance), while most modern construction homes will use a UFER ground which will be a different potential than the electrical ground.
Russ
Sorry.. I meant to say the cable ground will be a different potential than the house electrical UFER ground.
Wow - You nailed that one. I disconnected my cable box and presto! the hum disappeared. Now what? How do I eliminate it and still stay connected to the cable?
Awesome you got it figured.
I would switch to satellite myself :)
Here is a link, but $50 for a quality solution to a ground problem is majorly cheap IMHO.
Afterwards we discovered faith; it's all you need
I figure that if the cable company caused the problem they should provide a solution don't you? If we could get FIOS, I would seriously consider switching, but it won't be here for a while. I live in the boonies so to speak. - Thanks!!
You are right about the Cable company needing to fix it. Though I would be surprised if they will!
At least you figured it out. Often ground hums go unsolved.
Afterwards we discovered faith; it's all you need
I had a problem with my Motorola cable box causing a ground loop this fixed it and it's cheap
http://www.amazon.com/gp/product/B0017I3K9M/ref=oh_details_o03_s00_i00
Russ
I finally got the filter and hooked it up. It worked just fine. I was quite amazed. The noise has totally disappeared. I wonder just how it works. Is it just a filter of some sort? If so, what is it filtering? Thanks for the suggestion!!
Great! Which one did you use?
I used the $14.00 one. I believe that is the one you recommended. Thanks!!
Awesome!!
So glad to hear you licked it.
AFAIK it acts as a transformer and essentially breaks the ground connection
Afterwards we discovered faith; it's all you need
As the cable company has been silent on this I am going to try what you recommend. I will let you know how it works. Thanks for the help!! :)
This is what I bought (and paid twice as much). Issue resolved. It appears that you have the same problem. Good luck!
Hmmm, I need get home and look it up this evening but try that while I find the specs for what I bought to fix the problem. It is a filter that goes into the cable box. Nothing else worked for me.
Thanks Russ,
That was one of the ones I linked. Glad to know it worked.
Afterwards we discovered faith; it's all you need
That was my thought too. Also if there is any cable modem connected he could try disconnecting that too.
They make a piece for that
Afterwards we discovered faith; it's all you need
Dawnrazor - I posted that you guys hit the nail on the head. It is the cable. Is there any other way to get rid of it that does not cost $50.00? Is there a way I can perhaps ground the cable?
how exactly is your cable TV coax connected thru to your AV gear?
You can look into a coax isolation transformer to isolate the cabletv set top box from the outside coax line or you can try and isolate the audio lines coming out of the cabletv settop box or even use toslink optical for the audio if that is possible to potentially break the audio ground path. However you will still have a ground path thru the HDMI if you have that connected.
You said the magic word...HDMI as that is most likely where the path is. I was kind of baffled on this one so I really appreciate the help. I am going to get in touch with a friend of mine who works for the local cable company to see if they have a solution. It is their cable that is causing the problem so you never know, maybe they provide a solution that might save me 50 bucks. Thanks again!!
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