ground loop?

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

  1. luvvinvinyl

    luvvinvinyl Admin Staff Member Admin Subscriber

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    I think we have it. Someone please let me know that you are no longer getting the warning, please.
     
  2. Fisherdude

    Fisherdude Regular Dude - Super Mod Super Mod Subscriber

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    I got the warning this morning, but now I don't. Good job!
     
  3. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Nicely done :thmbsp: - no warning now.

    Thank you
     
  4. Contra

    Contra New Member

    Messages:
    2
    Long time reader, first time poster.

    I have a Technics 1200 MKII hooked into a
    Sansui RZ9500av &
    Techincs SH-50 GE

    I finally got the graphics equalizer hooked up, but now I hear a crackling noise from the left speaker. I've read up on ground loops and tried some simple fixes to no avail. I tried a different speaker to make sure it wasn't blown, everything was fine there. The crackling noise is only present when the graphic equalizer is turned on. Anybody have any hints?
     
  5. Copa1934

    Copa1934 My ears are bleeding

    Messages:
    9,884
    Location:
    Great Northwest
    Doesn't sound like a ground loop issue. If you haven't done so, you really need to clean with Tuner cleaner or Deoxit. We're talking a good soaking and working ALL controls, not just slides. Don't focus on just the left, do all banks and switches and whatever other controls there are. You won't be able to to do anything about electric relays as they are usually sealed and don't need attention. Everything must operate smoothly and EASILY.
     
  6. pilotprose

    pilotprose Active Member

    I have, or had the same problem with a DVD player. No matter what I did, this horrible hum was present. I solved the problem by simply building a circuit, that when I flip the swich, I terminate the inputs, or ground the input(s). The switch box is located only about six inches from the amplifier inputs. This solved the issue quite nicely. If you need the schematic for what I did, send me an message and I will forward it to you.
     
  7. pilotprose

    pilotprose Active Member

    hum

    termination box.jpg here is what I did to resolve the issue. apparently, the rca cables were acting as antennas and picking up noise that was being fed into the preamp of the amplfier. this just grounded the inputs when the switch was flipped, eliminating the hum so I could use the other inputs.
     
  8. TechRocks

    TechRocks Member

    Messages:
    64
    Marantz 2252B Hummmm!

    never noticed the hummm :sigh: until yesterday when it got much louder. Decided to ground the receiver to the ground screw on the wall plate...Guess what?!!

    IT WORKED!!! :banana: No hum just pure, clean, rock n' roll! :D
     
    Last edited: Nov 20, 2012
  9. TLCW

    TLCW Active Member

    Messages:
    156
    Location:
    Hong Kong
    With $600, I can buy a good used power amp like Onkyo M-508 or adcom GFA-585, integrated Sansui AU-9500 .
    Not even $59. I can buy a new tube DAC from China which I am considering.
    There are many threads on web about ground loop solutions to try.
     
    Last edited: Jan 1, 2013
  10. jneutron

    jneutron Member

    Messages:
    92
    I do not recommend you do this. It can be rather dangerous.

    You are now relying on the cable shield for protection against a hot to ground fault everywhere in your system. There is no guarantee that the cable will pull enough current to trip your breakers. That could leave a bad system hot to ground.

    You had the hum because of one of two reasons.

    1. Your cable system was earthed where it attaches to the house, but not bonded to your electrical system. Depending on where you live, the hv feed to you pole autotransformer (east coast) or transformer (west coast) has it's return currents shared by both the pole to pole neutral and the actual earth. The earth currents will form a gradient in the actual dirt, and if you do not bond the cable ground to the incoming line ground, you will see that as system hum. IF your cable in is not bonded to the house neutral/ground, you MUST have that done. Otherwise, a nearby strike could raise your cable feed voltage with respect to your house and neutral voltage, toasting anything connected to both.

    2. Your cable may be bonded at the service entrance, but because the cable arrives at your system along a different path from the AC branch circuit, you will have a severely large ground loop. A nearby strike will induce loop voltages proportional to the strike current rate of rise, and that can be very significant. You may already notice that thunderstorms, dishwashers, HVAC cause pops in your system, that is a really clean indication that the loop is communicating to your system signal path.

    Bottom line, I recommend you use a multiport surge protector at your system location. It needs to have I/O for your cable, any Ethernet, and any rca's. A multiport SPD will prevent induced voltages from a nearby strike from damaging your components by induction. And it doesn't have to be a very expensive one, you're only relying on it to bond all the input grounds to a common ground.

    When you do this, you may find that all your hum problems go away even when you remove that 3 to 2 adaptor..

    jn
     
    Last edited: Nov 15, 2013
  11. mycharlie

    mycharlie New Member

    Messages:
    20
    Location:
    Central US
    By grounding your equipment with the signal cables connecting the pieces, would a ground loop occur if you were to connect the equipment also from ground post to ground post and then to a true electrical earth ground (a rod buried 6')outside?
     
  12. jneutron

    jneutron Member

    Messages:
    92
    First: The outside electrical earthing rod has nothing to do with the system ground. It is an earthing conductor whose sole purpose in life is to protect you against a direct strike. It provides a path for a lightning bolt.

    Using large copper and tying all equipment together might help a specific problem, but it will depend on the problem itself.

    If the ground loop current causes an IR drop on either the IC shields, or on the grounding traces within the equipment, then yes, large solid grounds will help.

    If the large copper increases the ground loop currents due to lowered resistances, and the equipment is incapable of handling that additional current without coupling into the signal stream, you can make the problem worse.

    Coupling mechanisms of this variety will tend to be more apparent as the frequency rises. It may solve a 60 hz issue, but cause more hf buzz, noise, and sensitivity to external pops and clicks caused by dishwasher solenoids, HVAC compressor contactors, and lightning bolts causing pops in the system.

    Since consumer equipment has not been designed with this in mind, your results may differ from others. The best you can do is try the various options presented.

    A reminder to all. Never disconnect the safety bonding conductors. Never replace the safety conductor with a separate earthing rod, that can be very dangerous.

    jn
     
  13. Harlowsound

    Harlowsound New Member

    Messages:
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  14. miner

    miner AK Subscriber Subscriber

    Messages:
    1,055
    Location:
    Texas
    Hum X is the real deal. I had a ground hum I could only get rid of by lifting the ground and I was not comfortable with that so I purchased one of those noted in the above message. $75 well spent in my opinion.
     
  15. jneutron

    jneutron Member

    Messages:
    92
    If it is not UL listed, I would not recommend it.

    The internal diodes are not rated to survive a bolted fault or even a partial short.

    If one of the pieces of equipment fails hot to ground, it may blow the internal diodes before the circuit breaker can open.

    Leaving hot equipment.

    jn
     
  16. Rob41

    Rob41 Don't stop believin'

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    I have read of many others who hold Hum X in high regard as well.
     
    Last edited: Feb 17, 2014
  17. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I have never heard of Hum X.
     
  18. arcorob

    arcorob Addicted Member

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  19. iloveaudio

    iloveaudio New Member

    Messages:
    7
    It could be radiation of an trafo in your power chain or maybe try to swap the power connector 180 degree. Sometimes this can do the job... :)
     
  20. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Already mentioned in post #6
     
    Last edited: Jun 14, 2014

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