Got My Sherbourn - Love It & Concerned!!!

Discussion in 'AV Receivers' started by Thomas P., Apr 12, 2003.

  1. Thomas P.

    Thomas P. Stunt Coordinator

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    Well, I received the 7 channel Sherbourn yesterday and it is a beautiful piece of machinery. Set up was easy but when I fired it up I noticed one of the channels wasn't working so I rebooted it and all the channels began to work after the reboot. I was in 7th heaven until this evening when my fiance and I sat back to watch Harry Potter. During the quiet passages she noticed a buzz in the rear speaker. I stopped the DVD Player and went to check all of the speakers with the volume of the 4802 I am using as a pre/pro set to -30 (a low listening level). All of the speakers had a buzzing noise emitting from what seems to me to be the tweeters. I had t0 put my ear very near to the speaker to hear the buzzing. Is this normal for an amp? Should I be concerned enough to return the 115lb. beast? Opinions and experiences about this are very welcome.
     
  2. JohnKings

    JohnKings Stunt Coordinator

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    Thomas:

    My guess is you have a ground loop. Search for "ground loop" in this forum to find out ways to fix the problem. It probably is related to your cable or satellite connection. Try disconnecting your cable or sattelite connection from your system. I had the same problem with my Parasound amps and had to actually get an isolation transformer for my CATV (See link).

    Isolation Transformer

    John
     
  3. Thomas P.

    Thomas P. Stunt Coordinator

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    JohnKings, thanks for the reply but I don't understand. My cable is not connected to the pre/pro or the amp. Which cable do you mean? I have all my devices (except cable) running into the pre/pro and then connects and speakers running into the amp.
     
  4. Thomas P.

    Thomas P. Stunt Coordinator

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    JohnKings, I have got to admit that you guy's are pretty amazing. Anyway, even though I don't understand what one has to do with the other, I went and disconnected the cable from the cable box and it eliminated much of the problem but there is still a diminished buzz of the same nature emitting from the rear surrounds and the surround backs. The fronts and center seem fine. Any thoughts about this and in the interim I'll do a search on ground loop problems.
     
  5. Craig Woodhall

    Craig Woodhall Supporting Actor

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    Thomas,

    The cable doesn't have to be connected to the pre/pro itself.. the fact that it is in your house, all your audio/video stuff including your TV are plugged into the wall in your house, etc. they all interact or interfere in some way with each other.. some are luckier than others.. glad most of your buzz was taken away..

    Craig
     
  6. JohnKings

    JohnKings Stunt Coordinator

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    Tom:

    If you have done a search, you know by now that their are any number of things which can cause a ground loop including: large appliance(s) on the same circuit, dirty power, other users on the same grid in you neighborhood, etc.

    Unforunately, this is a very inexact science and it is more trial and error that determines the cause than anything else. Just so you know, in many cases it is all but impossible to relieve the ground noise completely. I have reduced mine to where I have to stick my ears up to the speaker to hear anything. That will just have to suffice!

    I guess what I am saying is if you can't hear it from the listening position - just forget about it and enjoy the music / movie!
    John
     
  7. Mike Up

    Mike Up Second Unit

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    Ground loops are strange beasts. I had a ground loop for a year and a half and didn't even know it until I used a different component hooked in to the system. It made all kinds of noise and the such.

    With cable TV and Satellite, the shielded ground must be connected to "ELECTRICAL" ground/grounding rod. Many cable/satellite guys don't ground to electrical ground. They either put in their own grounding rod or use the ground on a circuit, not the main ground that's attached to the grounding rod.

    What happens is that any grounding rod that's not connected to the "ELECTRICAL" grounding rod may have a different potential from the "ELECTRICAL" grounding rod. Hope you know electrical theory.[​IMG] So in essence, if one grounding rod has a lower potential than the other, there is now a circuit created, and it's called a ground loop.

    On your television, stereo, amp, DVD player, etc, all of the cable's ground conductors goes to the ground or common(that's another story). What happens is that those grounds reference true electrical ground. Now when you have a coaxial cable from the cable company or the satellite company, the shields in those cables are referenced to the "GROUND" that they are hooked to. If they are hooked to electric ground, they will be referencing the same ground potential as the electrics are referencing to. "NOW" if that coaxial cable is referencing a "NONE ELECTRICAL" ground, that coaxial cable's shield will not be turned into a "CIRCUIT". Electricity always looks for the path of least resistance to ground. If that coaxial cable ground has a lower reference ground potential, all the electronic component's will back feed through the coaxial cable's shield, seeing it as ground "INSTEAD" of the real "ELECTRICAL GROUND". Hence, a ground loop.

    The same can happen when electronic components are all hooked together through interconnecting cables. A ground loop happens when those electronic components are plugged into different breaker circuits. Since the wire paths of different circuits are of different lengths, one may have a lower resistance to electrical ground. So instead of an electrical current going to it's dedicated ground on it's circuit, it may see a ground on another component whose plugged into a different breaker circuit. This circuit could have the path of the least amount of resistance to ground. Hence, another ground loop.

    I have a Denon AVR-3803. A handful of people are having 60Hz scrolling hum bars of green and purple on their television screens while using the up-conversion circuit. Denon Jeff at the AVS Forum has stated that these problems are related to ground loops and RF injection(this happens from an improperly shielded Radio device). These people have never seen this problem before so are naturally accusing the Denon of causing this.

    This isn't the fault of the Denon, as "SOME" components will "SHOW" a ground loop. These people most likely have always had the ground loop, but never had equipment that made it's presence known. Since the up-conversion is converting one video format into another, it's electronics are directly converting one format's ground over to the ground of the other format. If any component or circuit is going to show ground loops, the Denon's up-conversion or any other up-conversion component would show it.

    These people have just been fortunate in not seeing a problem before using the Denon's up-conversion circuit.

    Denon has a 'fix' to make it less sensitive to ground loops by dropping the voltage down in the circuit. Since ground loops can have different severities, on a very high potential difference between two grounds in a ground loop, I wonder if the symptoms would still show even with the 'fix'. The simplest fix obviously being to fix the real problem instead of Denon making a work around that 'could' help.

    Hope I helped. Have a good one.[​IMG]
     
  8. Thomas P.

    Thomas P. Stunt Coordinator

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    Gentlemen, you did help and I appreciate the time you've taken to respond. To be honest Mike Up I'll have to read your post several times before I can get a handle on it. I went to Radio Shack and bought an isolation transformer but it hasn't helped; the buzz is back in all speakers. If I can't eliminate the the ground loop problem will it eventually affect my speakers or my other equipment. I can live with the noise it's making but would find it difficult to live with the thought that the ground loop problem is taking my equipment to an early grave.
     
  9. Mike Up

    Mike Up Second Unit

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    Thomas,

    I don't know if it would cause damage but it surely isn't helping. As for my situation with a Dish Network antenna(switched a little over a year ago to DirecTV), the installer didn't ground the dish or cable to electrical ground as is required by the state. He grounded with a separate none 'electrical' grounding rod that was not attached to the "electrical" ground. Every time I changed channels on the Dish Net receiver, I got very loud static through my home theater receiver. Also, the internal Dish 500 switch always had problems giving me an error if I changed channel up, then down immediately. While I don't know if damage could occur, I would definitely say there is a possibility and it's in your best interest to correct the grounding problem.

    If the cable tv coaxial cable or a satellite cable is not grounded properly, it could be a fire hazard. Correct grounding is needed for lightning strikes. If the cable and/or the dish antenna isn't grounded properly, a high voltage can be carried through the coaxial cable into the home. That cable could melt and start fire. That's beyond the damage high voltage would have on electronic components that could also start on fire from that over voltage.

    Good luck.[​IMG]
     
  10. Greg Conti

    Greg Conti Stunt Coordinator

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    Buzzing can be a pain. I've had it come and go as I switch out components. When I was using a Parasound pre/pro with Adcom amps, the buzzing was terrible. And even worse when I dimmed the lights. My current setup, a Sherbourn 7/2100 with a Lexicon MC1 is always dead silent. I think there may have been a little noise when I was using a Denon 2802 with the Sherbourn when I dimmed lights.
     
  11. Arthur Vino

    Arthur Vino Stunt Coordinator

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    problem solved! Parasound fault.. [​IMG])
     
  12. JohnKings

    JohnKings Stunt Coordinator

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    Tom:

    Are you sure what you purchased was the same type of isolation transformer I provided a link for in my post (see my first post)? As far as I know Radio Shack doesn't carry anything that - in and of itself - addresses this issue. I think I purchased the same thing tou did from Radio Shack when I first noticed the problem and, like your experience, it was no help. That said, the Dayton transformer solved the problem. I would highly recommend you buy one. They really do work!

    John
     
  13. Mike Up

    Mike Up Second Unit

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    John,

    Just out of curiosity, wouldn't fixing the problem be no more of a headache than trying to find a workaround?

    Fixing a ground problem isn't that much work and would seem to be an easier solution than trying to find an isolation source that works.

    Have a good one.
     
  14. Thomas P.

    Thomas P. Stunt Coordinator

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    Mike Up, childs play perhaps for you, Laddie, but my area of expertise is in enjoyin', not workin'. I always feel genuine alarm at the prospect of doin' too much work. [​IMG]

    JohnKing, I ordered the parts today. Many thanks.
     
  15. Lee-c

    Lee-c Second Unit

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    Thomas P.: The most common source for these hums is the cable t.v. connection. Below is a link to
    a device that will remove the hum caused by the cable t.v. You just insert it between the
    cable coming out of your wall and your t.v. or VCR, whatever the cable normally connects to.
    And presto, no more hum caused by the cable t.v.

    I've used this very device, and it removed the cable hum completely. It was just as quiet
    as when I had the cable disconnected, that's how thoroughly it worked. I highly recommend it. [​IMG]

    There can be hum caused by more than one thing, but this device will get rid of the cable t.v.
    part of the problem totally, in my experience. The name of the part you want is the VRD-1FF.
    Hope that helps. [​IMG]

    http://www.jensen-transformers.com/iso_vid.html
     
  16. Thomas P.

    Thomas P. Stunt Coordinator

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    Thanks Lee-C, I'll give it a try if JohnKing's suggestion doesn't work out.
     
  17. Mike Up

    Mike Up Second Unit

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  18. Albert Damico

    Albert Damico Stunt Coordinator

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    JohnKings and Lee-C both provided a link to sites that seem to offer the same device. I transfomer that sits between the cable and device to eliminate ground loop noise. But ine is $10 and one is $60. Are these the same devices? Why the huge difference in cost? Thanks
     
  19. Chu Gai

    Chu Gai Lead Actor

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    I might've missed it, but on the circuit where you've got your HT are there any lights (halogens) or dimmers? If so you can try turning them off to determine if there's any improvement.
     
  20. Martin Jiang

    Martin Jiang Agent

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    I had the same problem with my sherbourn, it drove me crazy until I found the source of the problem, The dimmer switch, when I turn it off all the buzz is gone, and when it's set to the highest, you can hear the buzz clearly, so I just stop using the dimmer for now
     

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