General Asylum

• Use one outlet - benhen 13:01:24 02/21/06 (0)
  In Reply to: Ground Loop Hum solution posted by saywhat on February 19, 2006 at 20:25:48:

  I've killed a ground problem by plugging everything into one outlet - that is - using both plugs of the same outlet. The problem I had was that I was using two outlets, both grounded, which created a ground "loop" that isn't fun to hear through your speakers.

  
  ----Component1----Outlet1---
  |                                               |
  |                                               |
  |                                               |---Ground
  |                                               |
  |                                               |-LOOP
  ----Component2----Outlet2---
  |
  |
  Speakers
  Hum

  
  ---Component1---Outlet1---Ground
  |
  |
  |
  |
  |
  ---Component2
  |
  |
  Speakers
  Silence

  
  
  

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• Start by identifying the source of the problem. - Al Sekela 14:30:31 02/20/06 (4)
  In Reply to: Ground Loop Hum solution posted by saywhat on February 19, 2006 at 20:25:48:

  While I'm not a big fan of Bryston equipment, I'd be willing to bet that your amps and preamp, with only the ICs that connect them, do not cause hum if plugged into a single circuit. The first step would be to confirm this. If you get hum this way, look at the interconnect cables.

  Second, be sure whatever AC power arrangements are required by using monoblocks do not cause the problem. Using different outlets on different sides of the room may cause a loud hum, for example, even if the two boxes are on the same AC circuit.

  If all this is OK, add the source components one at a time and see which one causes the hum. This component may be defective. Check the AC voltage between the audio ground (outside of RCA jack) on the output of this component and the input RCA jacks on the preamp, with no interconnect cable in place. Try reversing the plug if it is a two-wire device without a polarized plug. If it has a grounded chassis, there may be something physically wrong with it.

  If the offset is small but the hum is still annoying, isolation transformers will fix the problem at some expense to the sound. The Radio Shack device is of low quality and will degrade the sound in most systems. At one time, Steve Eddy manufactured a better quality isolation device. Contact him regarding his plans to offer this device again.
  
  

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  • I used this technique recently, but still,.. - Bambi B 18:31:11 02/20/06 (1)
    In Reply to: Start by identifying the source of the problem. posted by Al Sekela on February 20, 2006 at 14:30:31:

    Al Sekela,

    Perhaps it only that I have a ground loop hum problem and I 'm noticing that subject, but he last few days seem to have had an amazing outburst of hum problem posts.

    I had two simulataneous prblems with my audio/recodring system. I was running preamp, power amp amplification for a synthesizer, a recording mic pre, and a computer HD setup and was getting a teriible hum. I had never had all these compnetns toether previously, but by using the technique you mention of adding one component at a time to identify the source of the hum. I did this and in a few minutes discovered the Yamaha S90 keyboard and moreso the output of the M-Audio "2496" audio card in the computer made a nice steady hum. With those two items unplugged, the CDP and tuner sound great and without hum.

    I tried a bizarre rig of cords from across the room so that all comonents could be plugged into one power conditioner- thinking of somthing I 'd read about- "Common ground". But, no odd contraption of plugging helped and in some cases made it much worse- as when I plugged the S90 power into the power strip fot the television. I also unplugged the DSL modem and disconnected the network line to the computer thinking: "multiple grounds for one item".

    However, I've no luck, other than identifying the source of the hum.

    It mystifies me a bit as to why the two heavy and (originally) expensive power conditoners are not helping this situation. I'm using a 6 amp Powervar and big 11Amp Oneac (weight 41 lbs) and I was led to believe that these isolation transformer conditioners have the feature to- isolate ground. I'm not gettin mush of that benefit here. They do have some effect as the best results occur when everything that's conencted to the LS-3 gets it's power from one of the 8 conditioner sockets.

    I think my solution is going to have to be that the audio system and the S90/recording/playback will have to be separate systems- or a separate computer tied only to the audio system . Or possibly, if I can get the keyboard to run on the LS-3 system without hum,...

    Now I understand why in posters with this ground hum problem often claim to be driven bonkers.

    But, the real solution should involve a better understanding of what the technical reasons behind the hum are instead of these rambling tries with plugs and cords all over. It's impossible to diagnose the problem much less understand the cure if all I know is one symptom of the disease and nothing else.

    Cheers,

    Bambi B
    
    

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    • The problems are likely within the Yamaha and computer, - Al Sekela 11:32:37 02/21/06 (0)
      In Reply to: I used this technique recently, but still,.. posted by Bambi B on February 20, 2006 at 18:31:11:

      and there is nothing the power conditioner can do to fix them. If you get nice, quiet performance from the rest of the system plugged in to the conditioner, then the conditioner is doing its job.

      Since you have tracked down the problem, perhaps the audio isolation transformers discussed elsewhere in this thread would be the best way to allow you to use all your equipment together.

      Good luck!
      
      

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  • Re: Start by identifying the source of the problem. - saywhat 18:23:34 02/20/06 (1)
    In Reply to: Start by identifying the source of the problem. posted by Al Sekela on February 20, 2006 at 14:30:31:

    Thanks Al. I did some of testing of connections and found that I can eliminate 95% of the hum by removing the cable TV coax cable from either the wall or the back of the TV. What is left after that is faint, I can only hear it by turning the volume up all the way and putting my head next to the speaker (I won't worry about that). I had an Adelphia cable tech come and test the line and he said there was nothing wrong and that there was nothing he could do about it.

    So far I have found a Dayton Audio isolator for $10, a Sonance isolator for $57 and a Mondial Magic for $69.

    Thanks again. I appreciate the suggestions.

    Al
    
    

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    • You need a video isolator. - Al Sekela 11:27:07 02/21/06 (0)
      In Reply to: Re: Start by identifying the source of the problem. posted by saywhat on February 20, 2006 at 18:23:34:

      Your problem is common, and there are several transformers available to fix it. The basic problem is the same, but the cause is a ground loop between the safety earth connection of your AC power circuit and the safety earth connection of your cable TV installation. The cable is typically grounded where it comes into the house, and this is a different spot on your property than the place where your AC power is grounded. That difference in location leads to the offset voltage that causes the hum.

      The fix is a transformer that couples the TV signal but isolates the ground. You should use one of these and remove any audio transformer isolators from your audio system.

      The cheapest I've seen is the $10 Dayton video isolator. This should work well if you have typical cable TV.

      One that includes a surge-suppressor and that appears to be slightly higher quality goes for $40 here:

      http://www.elect-spec.com/video.htm

      There are better ones out there. Jensen has just come out with some new ones:

      http://www.jensen-transformers.com/
      

      • Dayton Video isolator from Parts Express   (Open in New Window)

      
      

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• These under $10/unit isolation transformers... - Hepcat 09:14:32 02/20/06 (0)
  In Reply to: Ground Loop Hum solution posted by saywhat on February 19, 2006 at 20:25:48:

  ...from Parts Express work like a charm. Cable TV inputs are usually the cause of bad hum in stereo systems.
  

  • http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=180-075   (Open in New Window)

  
  

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• Re: Ground Loop Hum solution - SWG 08:41:33 02/20/06 (0)
  In Reply to: Ground Loop Hum solution posted by saywhat on February 19, 2006 at 20:25:48:

  I had a hum problem which I isolated to my Tivo Direct TV unit. I bought a professional audio isolation transformer from Sweetwater.com, inserted it between the audio outs of the Tivo and my preamp, and the problem was solved. The price was about $45 including shipping. It does not degrade the sound from the Tivo enough for me to notice.

  I suggest you try to determine which component or components are causing the problem, then you will be able to find or purchase the most cost-effective solution.
  
  
  

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• Re: Ground Loop Hum solution - blackwax@mac.com 21:03:17 02/19/06 (0)
  In Reply to: Ground Loop Hum solution posted by saywhat on February 19, 2006 at 20:25:48:

  get a Ground Zero. its expensive and all i think it does is ties all equipment to a common ground, which you may be able to DIY much cheaper.

  i loosened a screw on the chassis of each piece of equipment and ran a groundings wire to a single ground and that helped some.

  other thoughts:
  isolation transformer
  dedicated circuit
  
  

  • http://www.graniteaudio.com/zero/index.html   (Open in New Window)

  
  

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