Can't get rid of speaker hum/static - AVS Forum
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post #1 of 20 Old 10-06-2008, 03:30 PM - Thread Starter
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I purchased the Panasonic SC-PT960 5.1 home theater system about 2 months ago. The system sounds great when pumped up loud, but since the day I hooked it up, the 3 front speakers (left, center, right) always have a constant buzz/static sound emminating from them as well. The wireless rear speakers always work perfectly fine. If there's music or a barage of sounds, it's hard to notice. When the scene features just dialogue or nothing at all the buzz is very noticeable. If I mute the volume or set to zero, the buzz dissapears. This buzz is present no matter which input I set it to.

I've read a lot about ground loops and have taken some steps to eliminate it. I use a Dynex 8 outlet Power Strip with coaxial protection. I've unplugged all inputs into the receiver to see if the sound goes away and it did not. I unplugged the power cords of all devices except the receiver and the sound persists. On different outlets, I've unplugged the fridge and a lamp; no change. Any help as to the cause of this would be appreciated. Could it be a defective unit? Are the outlets in my apartment outdated?

Here is a list of the items I currenly have in my entertainment center and their connection type:

LG LCD TV
Motorola Cable box (rca audio out to receiver; component video out to tv)
PS3 (hdmi out to tv; optical out to receiver)
Panasonic receiver (composite video out to tv)
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post #2 of 20 Old 10-06-2008, 03:43 PM
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sounds to me like that's the noise floor of the avr... and no, unfortunately, there's nothing you can do about it, nor is it defective... it's just the way it is... when you turn up the volume, you are amplifying the "noise" that the processing section of the avr is producing...

you say it goes away when you "mute/set volume to zero"... this would indicate that it's not a ground loop issue (60hz ground loops don't vary with volume)...

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

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post #3 of 20 Old 10-06-2008, 04:01 PM - Thread Starter
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Not sure if this helps as well, but the buzz doesn't grow louder as I turn the volume up. As long as the volume is not muted, the buzz is present. I do get fluctuations in it though, where you can actually hear the current grow louder and softer on its own. Rarely, it seems like its actually gone, only to come back a minute or two lately. I see other people with this system saying it works just fine. So frustrating for an audophile such as myself.
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post #4 of 20 Old 10-06-2008, 04:26 PM
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Does your panasonic system have a seperate powered sub woofer? If yes use a ground lifter on the sub. Have you tried using a ground lifter on the receiver?

ELITE LOVER FOR YEARS
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post #5 of 20 Old 10-06-2008, 04:49 PM - Thread Starter
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No, the subwoofer does not have separate power. It just plugs into the back of the receiver with the same speaker wire as the rest of the speakers have. What is a ground lifter and how do I do (use) it? The stereo receiver only has 2 prongs on the power cable, not 3.
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post #6 of 20 Old 11-08-2008, 03:38 PM
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I have the same problem JJ is describing with the Panasonic SC-PT960 home theatre system. I returned the system thinking it was defective and the replacement system still has static coming from center, left, and right speakers. I even bought a power conditioner and it didn't help. I live in a new house with a good electrical system so dirty power likely is not the issue. It isn't very loud static but it is disappointing because I bought Panasonic because of their reputation for high quality. Panasonic hasn't replied to my complaints. Disappointing.
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post #7 of 20 Old 11-08-2008, 10:52 PM
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All amplifiers have some noise, but it should not be more than barely noticible at low volume settings. By and large even inexpensive receivers and amps have respectable noise floors, so I would go with a defect or interference of some sort.

Ground loops can be tough to isolate, but a bit of detective work can often find the source. Check out some of the advice on the web and then start unpluging interconnects etc.

Other devices can be the source of noise especially if it is a buzz rather than a 50Hz hum. Dimmer switches are prime suspects. Motors are another. With dimmer switches about all you can do is try removing them, buying a new one or looking into the fairly expensive switch add ons that block noise. Dimmer and motor noise can travel on the power circuts or as RF and is usually not stopped by power strip "filters". Bad or missing grounding blocks at the cable service entrance often cause noise. Defective devices upstream on the cable can add noise. Disconnect the cable feed and if that stops the noise check for a missing or corroded ground block connection where the cable enters your house. The cable company owns the problem right up to that point.

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.
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post #8 of 20 Old 11-10-2008, 01:31 PM - Thread Starter
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I did the easiest check for a ground loop. I took my receiver and one speaker to a different room. Plugged it in and VOILA! Still that same damn static buzz hiss. Therefore, in a different room, with no other devices connected to the receiver other than one of the front speakers, it still makes the sound.

As a status update, I took it in for repair at the advice of Panasonic. They replaced the PC board inside but it did not fix the problem. Panasonic wants me to take it to another of their service centers. I am doing that today. If it doesn't get fixed this time Panasonic will replace. Sounds like I am getting the run around like Klymster.
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post #9 of 20 Old 11-10-2008, 01:52 PM
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Quote:
Originally Posted by JJGaucho View Post

I did the easiest check for a ground loop. I took my receiver and one speaker to a different room. Plugged it in and VOILA! Still that same damn static buzz hiss. Therefore, in a different room, with no other devices connected to the receiver other than one of the front speakers, it still makes the sound.

well, no, that didn't "prove" anything...

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector

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post #10 of 20 Old 11-10-2008, 04:59 PM
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Quote:
Originally Posted by ccotenj View Post

well, no, that didn't "prove" anything...

Does it not? If he has just the receiver powered up and no other powered sources are connected to it, there is no possibility of a ground loop external to the receiver.

There could be an internal ground fault or transformer induced hum causing the noise the OP hears, but not a ground loop that the OP can easily troubleshoot.

The remaining possibilities are noise traveling on the power line or as RF. Low frequency noise is hard to filter. A large value choke is needed.

So if not already done, it is time for the OP to check dimmer switches, fluorescent lighting and motors and to look out the window for a radio transmitter next door. Or pick up the receiver and speakers and go somewhere else and see what happens.

Oh, do you have any sound processing working when you hear the noise. Dolby PLIIx or Theater or the like. Do you have the same noise when you select just plain stereo?

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.
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post #11 of 20 Old 11-10-2008, 05:03 PM
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nope... he noted that he lives in an apartment (unless i misread)... unless he's SURE how the apartment is wired, there's no guarantee there's nothing else connected...

i agree with the rest of your post though...

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector

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post #12 of 20 Old 11-11-2008, 05:27 AM
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Also could be that the speaker wire could be running inside the wall next to another power supply. For instance if you have the speaker wire running next to the same electrical system that powers the microwave, then you would get that hum everytime the microwave ran...
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post #13 of 20 Old 11-12-2008, 09:40 AM
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You might try disconnecting the coax cable going from the wall to your Motorola box and see if that works. I was getting noise from my cable box even if I was playing DVD's or anything else.
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post #14 of 20 Old 11-12-2008, 10:42 AM
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Quote:
Originally Posted by FOCALSIBGUY View Post

Also could be that the speaker wire could be running inside the wall next to another power supply. For instance if you have the speaker wire running next to the same electrical system that powers the microwave, then you would get that hum everytime the microwave ran...

highly highly unlikely...

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector

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post #15 of 20 Old 11-12-2008, 11:06 AM
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The OP wrote:
Quote:


I took my receiver and one speaker to a different room. Plugged it in and VOILA! Still that same damn static buzz hiss. Therefore, in a different room, with no other devices connected to the receiver other than one of the front speakers, it still makes the sound.

There are only two connections to the receiver-
  1. power
  2. speaker

I would sooner expect that gremlins are the cause than that the speaker and speaker wire are the source. But he can put that to the test.
Use the shortest possible wire to connect the speakers (to rule out that it is acting as an antenna).

Use a portable AM/FM radio and tune through the bands looking for a loud noise, one that is similar to the sound heard from the receiver. Walk around the house and listen for the noise and a change in volume, go outside if needed. If the noise is from a motor or a bad power line transformer or dimmer you should be able to localize it. I owe this tip to a utility worker and it works. He used an AM radio to find a bad transformer 200" or so away from my house.

If it is your dimmer or motor, you can test it by disconnecting it or turning it off. If it is you neighbor's all you can do is ask, or look into filters and RF chokes (Snap-on ferrite chokes are readily available). If it is coming over the power lines from outside your utility company might be willing to check it and fix it if they own the source.

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.
-Bertrand Russell
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post #16 of 20 Old 11-12-2008, 11:20 AM
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i LIKE that am radio idea... i have to remember that one... thanks for sharing that tip...

- chris

 

my build thread - updated 8-20-12 - new seating installed and projector isolation solution

 

http://www.avsforum.com/t/1332917/ccotenj-finally-gets-a-projector

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post #17 of 20 Old 11-12-2008, 01:53 PM - Thread Starter
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Wow. So many responses as of late. Thanks all. I can definitely narrow it down to a few possibilities at this point. It's not the cable as I have disconnected that and it still made the sound. I have no fluorescent bulbs, and unplugging my lamp and refrigerator made no difference. I have reason to believe that the unit is defective, or I am getting interference, possibly from some sort of radio transmitter or power lines. Yes, I am in an apartment so I don't know if I share power sources with other units. There's cable/satelitte/power lines running everywhere outside my building! I'd have to take the unit somewhere isolated to test if it really is the unit. Does anyone here have this unit and can honestly say it works great? I am wondering if my ears are too sensitive, or maybe because I have a small apartment I sit too close to the speakers.
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post #18 of 20 Old 12-02-2008, 06:11 AM
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I too am having similar problems. I have a fairly complex system, Rotel amp, Rotel preamp, 3 400 disc dvd changers, satellite, slingbox, whole house audio sonos, tivo, DVDO IscanHD scaler, plasma etc. etc. along with x10 throughout the house.

I have a buzz across my three front channels, plasma off, problem is still there. My speakers are shielded, B&W 703's. I have so many wires running through my attic, poorly routed I may add. I wish I knew about potential interference issues years ago, at this point it would cost me a mint and weeks to rewire everything.

So I've taken the easy way out to see if I can eliminate my buzz/hum. I ordered a Tripp Lite IS1000 isolation transformer. I am hoping that if I plug the amp, pre-amp, satellite box and main DVD player into it, the issue will be gone. "Gone" as in "masked" since it obviously is still there.

Issues like this are troubling, time consuming and can be difficult to resolve. If your system is small, take it to a friends house and try it out. My guess is it it not your components......

You can try an isolation transformer, you probably don't need one as large as the one I ordered. You could also try to run a temporary ground wire from the chassis of your receiver to the wallplate and see if the noise goes away.

Love the idea of the am radio to narrow things down.
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post #19 of 20 Old 12-03-2008, 07:50 PM
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The isolation transformer did not solve my hum/buzzing problem.

I did figure it out my problem after rewiring my entire closet! What I found was if I removed my component video cable from my DirecTV box to my preamp, the hum would go away.

So what is the problem?? I don't know. I replaced the component video cables, same problem. The Satellite dish is grounded correctly. I would guess t is one of two things. There is either a problem in the video circuit of the pre-amp, or there is a problem with the DirectV receiver. I have a new receiver on the way, we will see if that solves it.
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post #20 of 20 Old 12-04-2008, 07:27 AM
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Check wall sockets in other rooms. I had speaker hum, and I checked wall swithches in other rooms that could have been interfering. YEP The switch in the kitchen upstairs was the culprit. When someone turned the kitchen switch on it made the speakers hum.
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