Dedicated Circuits - To All Users Of

Discussion in 'Archived Threads 2001-2004' started by Ron Duca, May 7, 2002.

  1. Ron Duca

    Ron Duca Stunt Coordinator

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    The issue - I just added a Sherbourn 5/1500A (200x5) amplifier to my system and am now using my Yamaha RX-V995 receiver as a pre/pro. Since this addition, I have noticed that I am getting electrical interference from nearby light switches, especially those with dimmers. I can eliminate this interference by using a cheater plug on the amp, but this is not safe and I need a permanent solution. I have been told by many that adding a dedicated circuit would solve my problem. However, after looking at the wiring in the breaker box for my house, which is less than one year old, I don't see how a dedicated circuit would provide anything more than a full 20 amps of current for my audio/video equipment.

    The reason I'm pessimistic about this is because my house wiring is like this: Each of the hot wires coming into the breaker box go directly to an individual breaker. However, ALL of the neutral and ground wires are connected to the same neutral/ground bars, one bar on each side of the breakers tied together with a metal plate across the bottom. I'm not sure what these bars are called. This explains to me why I get interference from light switches in the same room and from some in adjoining rooms. How would adding another circuit and tying into the same neutral and ground connections as everything else eliminated any electrical interference?

    Has anyone ever looked at how their dedicated circuit is wired at the breaker box? Is it totally isolated with a separate ground? If so, how did you do it?

    Thanks,

    Ron Duca
     
  2. Frank_S

    Frank_S Supporting Actor

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    Ron, I'm no electrician but I have read that you have to be very careful about adding separate grounds. I would recommend checking out www.avsforum.com and going to the audio/video improvement section. Perform a search under "dedicated circuits" there is a LOT of info regarding this subject. Good luck! [​IMG]
     
  3. Steve Zimmerman

    Steve Zimmerman Second Unit

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    I added a dedicated circuit in an attempt to reduce ground loop hum and it did not help. I'm glad I have the dedicated circuit, but only for overload relief not for any cleanup of the signal.

    --Steve
     
  4. Wayne A. Pflughaupt

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    Steve,
    A ground loop means you have more than one path to ground in your system. Installing a dedicated circuit will not fix that problem. The most common causes of ground loops are:
    • A cable TV feed that is not properly grounded at the entry point to the home, or perhaps has a ground problem someplace upstream.
    • A satellite installation where the installer did a “quick and dirty” ground to a water pipe or something similar.
    Ron,
    What kind of “interference” are you getting? The problem most people have when they introduce an amp with a grounded plug to their system is a ground loop, but I get the impression this is not the problem in your case.
    Brucek can do a better job of explaining the technicalities of electricity than I can, but a few things do come to mind.
    First, since you don’t have a dedicated circuit, I would expect right off that the lights you are having problems with are sharing the same circuit as your amp.
    If this is not the case, next I would expect that the circuit the lights are on is connected at the service panel to the same phase (or leg) as the circuit the amp is on.
    If the latter proves to be the case, I would question the quality of the power supply in the amplifier. It shouldn’t be so readily susceptible to this kind of interference (again, assuming the problem is not a ground loop).
    All that aside, an amp this powerful deserves a dedicated circuit, if for no other reason than to insure it has maximum current flow and to minimize line fluctuations to the more delicate source components.
    Regards,
    Wayne A. Pflughaupt
     
  5. Ron Duca

    Ron Duca Stunt Coordinator

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    Wayne,

    You said, "First, since you don’t have a dedicated circuit, I would expect right off that the lights you are having problems with are sharing the same circuit as your amp."

    I'm not exactly sure what makes up a circuit. My service panel contains 20 pairs of circuit breakers. Is that 20 circuits or 40? Anyway, I do know that the wall outlets in my living room are controlled by a different "circuit breaker" than the lights in that room. Does that mean they are on different circuits?

    Also, the top of the outer wall, where my equipment is, is inaccessible from the attic. We would have to cut a hole in the wall to run electrical wire up into the attic, rather than down from the attic. I'm not sure we're ready to do that to our fairly new house. I was hoping someone would confirm that a power conditioner would resolve this problem, but it looks like I might be removing the dimmer switches instead.

    Ron
     
  6. John Royster

    John Royster Screenwriter

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    Ron,

    You might want to confirm that your lights and electrical outlets are indeed on different circuit breakers. Most times they are not, even though it is against electrical codes I believe.

    Second, dimmer switched are known to cause power problems and interference. That is a pretty hefty amp and could certainly use its own 20 amp circuit.
     
  7. Steve Zimmerman

    Steve Zimmerman Second Unit

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  8. Wayne A. Pflughaupt

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    Ron,

     
  9. Ron Duca

    Ron Duca Stunt Coordinator

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    Wayne,

    After I get everything powered up, there is a very low level buzz and hiss coming from the speakers. When I turn on a light switch in the same or adjoining rooms, it produces a slight tick sound. And when I turn on a dimmer switch, the low level buzz becomes a slightly louder buzz. It sounds like electrical interference. As I dim and brighten the lights, using the dimmer switch, the interference becomes louder then softer.

    Also, my amplifier has a sleep mode where it goes to sleep after a few minutes without receiving a signal, normally from the receiver. However, after it's gone to sleep, I can awaken it by flipping a light switch. That slight "tick" sound that is produced is just enough to trigger the amp.

    I did some testing and found that the amp does not wake up unless it is connected to the receiver, via interconnects. Does that mean the receiver has something to do with it? The receiver has a two prong cord whereas the amp has a three prong cord.

    I also ran a long extension cord to a back bedroom and found the noise floor to be quieter and I could rarely wake the amp by flipping light switches. Maybe I'll have an electrician swap outlet circuits between the one in my living room and the one in the spare bedroom.

    Ron
     
  10. LewB

    LewB Screenwriter

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    Just a shot in the dark here but ...

    Could this be caused by a loose common or ground wire in the panel ? Perhaps the electrician could check that for you too ? Or you can do it if you feel comfortable working on the panel yourself.
     
  11. Bob_M

    Bob_M Stunt Coordinator

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    Hi Wayne

    >There are a few different breaker panel configurations on the market, so it might be tricky to figure out which phase a circuit is connected to.<

    Hmmm, how about look for the 220V breakers? You know each side of the breaker must be on a different leg. That should give you a good idea as to the scheme the box is using.

    >Some panels have the entire left bank of breakers on one phase and right bank on the other. <

    I have never seen one of these. How would you install a 220 volt breaker in this case?

    Bob
     
  12. SanfordL

    SanfordL Stunt Coordinator

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    I have read many times how dimmers throw lots of noise into the circuit. I don't remember the specifics, but basically it's something to do with the fact that the full electrical load does not go to the light, the left over electricity gets fed into the line leaving you with spikes and noise. Of course, if you have a groud loop, that's something different, and it sounds like you do b/c the cheater resolves the problem. You might try removing the dimmers from the circuit by unistalling them and putting in switches (on / off) and see if it helps, but I imagine Wayne is right and you have a ground loop. Particularly based on the fact that when you plug the amp into another room, it can still get tripped by a light switch in your HT. I assume the outlet in the other room is on another circuit, right? Good luck.
     
  13. Kevin C Brown

    Kevin C Brown Producer

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    There's actually a thread on the Outlaw forum, 950 saloon that talks about ground loops and other sources of hum in a system. (Mostly CATV related.) A lot of people say that most times, AC power "filtering" helps, and balanced power helps too.
    Before I got a balanced power unit, I had hum problems too. I had also heard that using cheater plugs wasn't a "long term" solution, but that's exactly what I did, for many, many years... YMMV I reckon! [​IMG]
     
  14. Ron Duca

    Ron Duca Stunt Coordinator

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    I solved this particular problem and only have one more to go. My problem was not so much with hum, but more with a buzzing that sounded like electrical interference. I could eliminate the interference by using a cheater plug on the amp or by disconnecting the ground wire on the outlet. Neither one of these are real safe, so I decided to replace my standard wall outlet with a GFCI outlet. It is internally grounded, and does not use the ground wire, which is tied into every outlet and switch in the house that does use a ground wire. I am not receiving any interference from light switches or other devices, even the dreaded dimmer switches.

    Some of you may disagree with this solution, but it works for me. Thanks for all of your advice.

    I still have an issue with my system, but I believe I'll start a new thread for it since I feel it is unrelated to this issue.

    Ron
     
  15. Wayne A. Pflughaupt

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    Bob,
     
  16. brucek

    brucek Second Unit

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    Ron,
    Wayne has nicely answered most of your questions already, but I may be able to add a few comments.
    Light dimmers are usually some form of triac which is gated on and off to feed the lamp less than the full AC cycle of power. The amount of the cycle used determines the bulbs brightness. The triac will be triggered on during the positive and negative cycle and will turn off at the zero crossing. The problem comes when the triac is triggered on each cycle and a large amount of switch-on current causes noise that is usually taken care of by a filter in the dimmer itself. Obviously some dimmers are noisier than others. Either way, they can introduce noise and spikes on the line and create unwanted potential in the ground circuit.
    If they are located in the circuit you are using for your HT system, this is a sure recipe for noise in both the line and in the ground. If they are located on a different circuit, but the same leg as your HT, the problem will be less. If they are located on a different leg, the problem is lessened even more.
    When the dimmers are on a different circuit than your HT, most of the noise will be attenuated at the service panel because of the extremely low source impedance of your mains and will not travel out the other branch circuit to the HT system. If the noise is particularly high, the service panel attenuation will not be enough to completely sink this noise and you can still be affected on branch circuits. Certainly if the electrical cabling of your house is physically run together in areas where one circuit is carrying a lot of noise it can be mutually conducted to surrounding cables.
    Certainly for a dedicated circuit to be connected to the panel leg of your choice and run directly in an unaffected location to your HT system without multiple interconnections along it's path is an advantage. This obviously provides the cleanest, lowest impedance path to ground and a line unaffected from other sources. If you had a dedicated line to your HT and ensured your dimmers were located on the opposite leg of your service panel, it would go a long way to lowering the effect of the dimmers.
    Once you had done this, you could then add a balanced power unit as I was mentioning in the other thread on this subject (see Waynes post). With these suggestions in place I strongly suspect you won't be affected with any buzz.
    A GFI receptacle when wired properly is basically no different than any other receptacle in it's connections. It has a line and a neutral and a safety ground (unless it's an ungrounded type - bad idea). It's function is to monitor the amount of current flowing in the safety ground by ensuring that the hot and neutral currents remain equal. The safety ground is a cold conductor and shouldn't have any more than a few milliamps flowing in it. There will almost always be some potential in your safety ground for various reasons that I won't go into here. All the current that flows from the hot conductor through a load should flow to the neutral. If the difference is more than a pre-defined amount, the GFI receptacle will trip - that's it... There's certainly no harm in using one if you want - just be sure it's wired properly - because it's not likely to remove the noise the way you described unless it's wired improperly.......... [​IMG]
    brucek
     
  17. Richard_s

    Richard_s Second Unit

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    I have seen many grounding/ground loop problems caused by improperly installed outlets. If the Hot (black) and neutral (white)leads are reversed when installed the grounding will be a mess. Also if things are not tied together properly at the power box this too will cause problems. I would buy an outlet checker and check all outlets you are using. Here is one possible source ( I am sure local hardware/elec stores will have this item I think Sears sells them):
    http://www.suttondesigns.com/fred2.html
    Maybe when you installed the GFI you wired the outlet correctly whereas before the outlet was backwards (just a thought).
    EDIT: go to www.sears.com and search on "circuit tester". The GB Electrical for $8.99 should be good enough.
     
  18. Bob_M

    Bob_M Stunt Coordinator

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    Richard,
    >Maybe when you installed the GFI you wired the outlet correctly whereas before the outlet was backwards (just a thought). <
    Possibly, but what Ron did was lift the Ground wire from the GFCI. Similar to using a cheater but a little safer (I hope [​IMG]). I do know under certain circumstances NEC allows a GFCI in places where no equipment ground conductor is present.
    Bob
     
  19. Richard_s

    Richard_s Second Unit

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  20. Ron Duca

    Ron Duca Stunt Coordinator

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    I hope it's safe too.

    I had an electrician come out the other day. He tried several things trying to eliminate the interference, including creating a separate ground of some sort for the circuit feeding my living room outlets. He spoke to someone at his shop and even called Leviton. He had already tried everything they suggested except for lifting the ground and using a GFCI outlet.

    I'm a bit on the neurotic side, so this whole thing still bugs me. I've talked to seven electrical contractors and all but one of them didn't even want to get involved with something like this. I also spoke to six local so called "home theater" installation companies and everyone of them said they only did low voltage stuff. Most of them appear quite ignorant of such an issue. One guy even told me that since I had purchased my equipment from different stores and used different brands, it was a wonder any of it worked. What's up with that? How many of you have equipment of all the same brand that was purchased from the same dealer?

    Like I said, it bugs me that the ground had to be lifted to eliminate the interference. My wife keeps telling me that she never had these problems with her $89 all-in-one system she got from Wal-Mart ten years ago. I really like the sound that my new amp brings to my system, but it sure has magnified some imperfections in the house's electrical system. Maybe I'll have to go back to my receiver.

    OH Nooooooooooooooooooo!!!!!
     

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