Plasma TV causing hum in amplifier

Discussion in 'Displays' started by Brian Perry, May 16, 2009.

  1. Brian Perry

    Brian Perry Cinematographer

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    I recently replaced my LG plasma with a Panasonic plasma, and while the picture quality is about the same, I am now experiencing some hum in my Bryston amplifier. The hum is only present when the TV is on. It is not a constant hum, but more of a 3-seconds on, 3-seconds off type of hum or buzz.

    Do you think this would be an issue with the TV? As I said, I didn't have the problem with my LG plasma and my system was all interconnected the same way. Should I go through the standard checks for finding ground loops? I thought those types of noises were constant -- this is definitely an alternating hum/buzz. It is not coming from the TV itself but from the amp. In fact, I switched out the Bryston for a Meridian amp I have in a secondary system and the hum was even more pronounced (but followed the same on/off pattern).

    Thanks
     
  2. Joseph DeMartino

    Joseph DeMartino Lead Actor

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    Sounds like an issue with the new TV's power supply - either there is something wrong with it, or it draws a lot more juice than the old TV's and therefore overloading your system in a way the old one never did.

    I'd still do all the standard checks for a ground loop, reseat all the power and signal cables, etc., just on general principle, and to make sure that nothing got knocked out of whack while you were disconnecting and reconnecting things. But then I'd look at the power issue again.

    Do the TV and amp share the same electrical outlet or surge protector? Do you have any power conditioning equipment anywhere in the mix? Is the HT equipment on the same electrical circuit as a refrigerator or other appliance that draws a lot of power? If the interference isn't coming from the signal path it has to be coming from the electical side - those are the only two things connecting the amp and the receiver.

    BTW, when you say the hum is in the amp - do you literally hear a sound coming from the box itself, or are you hearing the buzz/hum in the speakers? If the latter, are you hearing it in all of the speakers, or just some of them?

    Regards,

    Joe
     
  3. Brian Perry

    Brian Perry Cinematographer

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    Thanks Joe...it does appear to be an issue with the TV power supply. When I connected the amp to a different circuit, the problem went away completely. Now I need to decide whether to bother investigating whether the plasma TV is defective or if this is "normal" -- even though it's under warranty, it's a pain to go through the hassle of bringing it back or calling a tech to come out.

    I may just leave things as they are -- in fact, the amp was connected to a Monster surge protector and now it is just plugged straight into the wall outlet. Who knows, I may even get better performance from the amp, if like some people say, surge protectors can limit an amp's power.

    Thanks
     
  4. Joseph DeMartino

    Joseph DeMartino Lead Actor

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    Living as I do in Florida, the lightning capital of the United States, I wouldn't plug a desk lamp directly into a wall outlet. [​IMG] I've never heard of surge protectors (or battery back-ups, which I prefer even over those) as limiting an amp's power. They should put out 110 VAC and the amp's power supply should have no problem dealing with that. A UPS should make up for any power fluctuations.

    If possible I'd connect a UPS or a surge protector to the wall outlet the amp is plugged into, and then plug the amp into that.

    I'd also take a look at the power stats of the new TV vs. that of the older one. If there is a substantial difference in power consumption, I'd be inclined to think that the new set is fine and that the power increase alone was enough to stress your electrical system in a way the old set didn't. If the two sets are close to the same values for power usage, it is more of a toss-up as to whether or not there is an actual problem with the new set's power supply.

    I also do still wonder if some third item unrelated to your HT may have not have been contributing to the issue. Not long after I moved into my ancient condo I had some electrical work done, and one of the first things I did was have the outlets on the wall where the HT was going to go placed on an isolated circuit. They had previously been on the same circuits as some of my kitchen items. Not a good idea.

    Glad to hear you've solved the problem. But do think about that SP or UPS. [​IMG]

    Regards,

    Joe
     
  5. Clinton McClure

    Clinton McClure Casual Enthusiast
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    I agree with Joseph.
     

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