ground loop?

Discussion in 'General Audio Discussion' started by VQLT, Jul 30, 2003.

  1. Bobby D.

    Bobby D. Active Member

    I had the same problem with a ground loop between my house ground and the cable ground. I put a 3 to 2 prong adapter on my home-make amplifier and the hum was gone. The cable box is now the sole ground in the system (through the coax cable). The rule of thumb here is to allow no more than one external ground. I have never seen any commercial HiFi components using the ground prong in the power plug. Components are usually designed to "float" with respect to the mains.

    If the hum persist but goes away when you unhook the cable line, there's a trick to isolate the cable box from the cable ground. Take two balun transformers (the adapter people used to use to hook cable up to old TVs that took twinlead) and connect the twin lead outputs of one to the other. Now you have a 1:1 RF transformer that breaks the ground loop. I would only try this as a last resort. Now that cable is a two-way digital system, the baluns might mess up your cable reception.

    Bobby D.
    Last edited: Dec 29, 2009
  2. stevet66

    stevet66 Member

    I solved my ground loop problem the saqme way, I went and bought the Hum X by Ebtech and now the hum/buzz is completely gone! This is also the safe way of doing it cause everything is still grounded. It cost me $70. Not bad.....
  3. Copa1934

    Copa1934 My ears are bleeding Subscriber

    I too have the hum, and it is not good. :)

    I've been following these posts and tried reversing the plug (not polarized) and still have hum at no volume. Nothing is connected to the receiver other than rabbit ears. I had another receiver in it's place, plugged into the same A.C. and no hum.

    Seems to be narrowed down to the receiver, but what in the receiver can be corrected to eliminate this?


    Last edited: Jul 25, 2012
  5. Copa1934

    Copa1934 My ears are bleeding Subscriber

    Very cool and very helpful. However, my situation is a little different in that I have a standalone system, ie nothing connected but the speakers. I've turned off flourescent lamps and other "things" on the same circuit and still hear a hum, very low and faint. I suspect it's the system, unless of course due to the wiring (which is 60+ years old) may be shared on another outlet, where some other device is the culprit?


    Last edited: Jul 25, 2012
  7. raindance

    raindance Member

    No-one is listening to your question. Explain to me what receiver you are referring to that has the issue. If it is a tube receiver, some slight 60Hz hum in the speakers may be normal. If there is excess hum, usually it indicates that one tube in a push pull pair is biased way different to the other, or your smoothing caps are toast.

    If you have a solid state receiver, your smoothing caps are probably toast.

    I assume you are testing with the volume all the way down? Not set to the phono input?


    Last edited: Jul 25, 2012
  9. Copa1934

    Copa1934 My ears are bleeding Subscriber

    You say bad caps and hum go hand in hand, why not just state that from the start rather than make all the unrelated and unnecessary commentary prior to that?

    If bad caps, then where do I start? What are the most likely points to check? Is it as simple as looking for deformed caps and then moving from there? If bad caps are located, and equivalent replacements are not available, is there a tolerance that is acceptable, i.e. can a cap with a slightly different value be used with little impact on performance? If not than the receiver may be a lost cause.

    I don't know how it will help but the unit is a Realist STA-860 page 10

    As a side note, some people would say chuck the sucker, it's not worth it. If it can't be fixed, OK, but I try to live by the three R's and would just assume not add more HiFi to the local landfill if it can be avoided. Our love of vintage products does more than just keep the spirit alive, it keeps loads of cool stuff out of our landfills.

    Thank you!
  10. michaelhigh

    michaelhigh mind's eye music

    I have an Ampeg bass amp that has no polarity switch. If I hook up a bass pre amp (which I do for added tone and EQ) and wireless I can get some hummage from the amp. I have an Ebtech Hum Eliminator which breaks ground loops and quiets everything down well. You may look into a device such as that. You simply start with the offending member, plug the AC into the Hum Eliminator, then out to the wall as usual. Works miraculously to get the noise floor down dramatically...


    Last edited: Jul 25, 2012
  12. Copa1934

    Copa1934 My ears are bleeding Subscriber

    The way in which you approach the answer, in the second paragraph (installment if you will) was more what I was looking for. The prior post, to me anyway, came across condescending. This latter part is very professional and far more informative.

    Now I have something to work with. My main issue now is whatever pots I can't visually identify as potentially bad, I'll have to rely on other sources (people) to assist or simply perform the work. Can't justify the cost of equipment to do it, unless it's something I can buy cheap (working) on eBay?

    I'll check for deformed/bleeding caps and then go from there. I'm going to put in a separate post looking for a knowledgeable/trustworthy repair place in the area (likely will not be local, too small a community). Maybe find a good hobbyist?

    Thank you very much for that more enlightening response!!!
  13. amapimp

    amapimp Member

    Is the cdr player stacked on top or underneath of the amplifier????
  14. Brent87st

    Brent87st New Member

    It is hooked to the "aux" jack, not a phono jack??
  15. 1newbe

    1newbe Active Member

    Interesting thread guys, very informative. Thanks.
  16. mightynutmeg

    mightynutmeg fcbarça nut, ee student

    As mentioned previously, I have had great sucess with the radio shack isolation transformer. Hook it up between your trouble component and your preamp.

    In my case I had two power amps (L and R) and an obvious ground loop between them, so I connected the isolation xformer between the source and amps. It's under $20 and at that price it is definitely worth trying out. If it fixes your problem but you are not satisfied with it (it does have rather cheap connectors and cabling on it...) return it and then feel confident ordering a special audiophile isolation xformer.

    This is a great device for people that connect a computer to their stereo as well.

    radio shack #270 054

    R.e. recapping... The joke I give is, when tantalums fail, they leave two marks... A black one on the board, and a brown one in your pants.

    an undergrad hooks up an electrolytic backwards at least once a quarter, always quality entertainment...
  17. transmaster

    transmaster Super Member

    If that cured the problem then you need to check the wall socket you where using there is a problem there. The easiest and safest way to check it is get your self an AC circuit tester. These are so handy to have you will wonder how you got by with out one. You would have discovered the problem in a much shorter time. The one linked below is $39.95 it is made by Extech which is my favorite brand for this type of test equipment think of Extech as the Simpson's of China.

    Attached Files:

  18. transmaster

    transmaster Super Member


    One of the thing you need to do is check is to make sure your wall plug is wired correctly. If it isn't it can cause all kinds of problems. Checking is easy get yourself a circuit tester the are cheap, less the ten bucks.
  19. petehall347

    petehall347 the brandy coffee man

    just tried clicking to page 2 from page 1 .got a warning about viruses this might be a false positive but i don't think so as i very rarely get these warnings
  20. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Attention Moderators !

    For me its page 4 (after post #45 - our page displays must be set up differently :smoke:) - Malware warning - referencing the URL you quote above.

    Can the Mods take a look at this?
    Last edited: Jul 1, 2012

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