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Discussion Starter · #1 ·
Hello all,


We just had our home theater system installed. In the same room as our home theater, we have a ceiling fan and a gas fireplace (with a switch to turn it on because it has electronic ignition). When we turn on the ceiling fan or fireplace switch, some distorted noise comes through the speakers. It is very noticeable and quite loud through the powered subwoofer. Is there anything we can do about this. We're a little nervouse about why this is happening and its effect on the speakers, electronics, etc. Thank you.
 

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Do you literally mean the sound only happens at the moment you turn things on (and then goes away)? Or do you mean it starts when those things are on and keeps going as long as they stay are on?


In either case this is interference getting in to your audio system, but the solution could be different.


Dimmer switches often add interference by entering the system as a "ground loop" -- power travelling between devices along the shield side of the cables. Basically they put noise on the ground line of your power outlets.


Start up interference from a fan motor or the electronic sparker of the fireplace, on the other hand, may simply be entering through cables that are not well shielded enough, particularly if you have cable runs inside the walls that are near the power lines that feed those.


In either case the subwoofer will be the speaker that reproduces this the most since the interference will be in the low frequencies (i.e., 60Hz).


You may need to have the ground connection for your fan and fireplace starter re-checked. You may need to replace cables with better shielded cables. If you have long cable runs between pre-amp and amp (as is typical for example with the cable run to the amp built in to the subwoofer), you may need to switch to "balanced" connections that are better at rejecting interference. This may mean having to replace some equipment, since not all equipment has XLR (balanced) sockets.


Checking for ground loops is tricky, and eliminating them is even trickier. If your subwoofer has a three prong plug, get one of those "cheater" 3-prong to 2-prong adapters and temporarily put it on that plug (without hooking up the "ground wire" on the 2 prong side) and see if that eliminates or significantly reduces the noise. Try both ways of plugging in the 2-prong side, since one way may reduce things more than the other. If the noise reduces or goes away, then you do indeed have a "ground loop".

--Bob
 

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Discussion Starter · #3 ·

Quote:
Originally Posted by Bob Pariseau /forum/post/0


Do you literally mean the sound only happens at the moment you turn things on (and then goes away)? Or do you mean it starts when those things are on and keeps going as long as they stay are on?


In either case this is interference getting in to your audio system, but the solution could be different.


Dimmer switches often add interference by entering the system as a "ground loop" -- power travelling between devices along the shield side of the cables. Basically they put noise on the ground line of your power outlets.


Start up interference from a fan motor or the electronic sparker of the fireplace, on the other hand, may simply be entering through cables that are not well shielded enough, particularly if you have cable runs inside the walls that are near the power lines that feed those.


In either case the subwoofer will be the speaker that reproduces this the most since the interference will be in the low frequencies (i.e., 60Hz).


You may need to have the ground connection for your fan and fireplace starter re-checked. You may need to replace cables with better shielded cables. If you have long cable runs between pre-amp and amp (as is typical for example with the cable run to the amp built in to the subwoofer), you may need to switch to "balanced" connections that are better at rejecting interference. This may mean having to replace some equipment, since not all equipment has XLR (balanced) sockets.


Checking for ground loops is tricky, and eliminating them is even trickier. If your subwoofer has a three prong plug, get one of those "cheater" 3-prong to 2-prong adapters and temporarily put it on that plug (without hooking up the "ground wire" on the 2 prong side) and see if that eliminates or significantly reduces the noise. Try both ways of plugging in the 2-prong side, since one way may reduce things more than the other. If the noise reduces or goes away, then you do indeed have a "ground loop".

--Bob


Hi Bob,


Thank you so much for your help on this. Yes the noise only occurs when I initially turn on or off the gas fireplace and/or ceiling fan speed selector switch, then the noise immediately goes away. The installers did use a "cheater" adaptor which is a 3 prong to 2 prong electrical adaptor for the subwoofer. This helped a little bit, but not much. Should I use this "cheater" on other components? Right now the installer is recomending the use of a high-end surge suprressor to possibly remedy this problem. Do you think this will help?


The other problem I am having is that when components such as gaming systems, dvd player, etc. are hooked up directly to the receiver (brand new NAD T773), I get white horizontal lines and a wavey/bouncy picutre. The installer then hooked the dvd player up through the TV and these issues go away. The audio sounds great, but we're concerned about electrical/equipment issues. Thanks Bob...
 

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Quote:
Originally Posted by jag3299 /forum/post/0


Hi Bob,


Thank you so much for your help on this. Yes the noise only occurs when I initially turn on or off the gas fireplace and/or ceiling fan speed selector switch, then the noise immediately goes away. The installers did use a "cheater" adaptor which is a 3 prong to 2 prong electrical adaptor for the subwoofer. This helped a little bit, but not much. Should I use this "cheater" on other components? Right now the installer is recomending the use of a high-end surge suprressor to possibly remedy this problem. Do you think this will help?


The other problem I am having is that when components such as gaming systems, dvd player, etc. are hooked up directly to the receiver (brand new NAD T773), I get white horizontal lines and a wavey/bouncy picutre. The installer then hooked the dvd player up through the TV and these issues go away. The audio sounds great, but we're concerned about electrical/equipment issues. Thanks Bob...

Your noise could be voltage loss when the fan is turning on, but it is pretty unlikely your fireplace sparker is using anywhere near that much juice. I suspect you may need to use better shielded cables.


Diagnosing this stuff, and your video interference through the receiver, is tricky. You have to start with a minimal setup and then start adding things in, in different combinations, until you find where the problem seems to be coming from.


Ground loop interference, for example, often comes in on the feed for your cable TV -- when it hasn't been propely grounded at the point where it enters your house. This one's easy to spot if problems go away the moment you disconnect the cable TV feed from the back of your cable TV receiver.


Sometimes adding in gadgets meant to filter out this stuff -- video filters for example -- can just make things worse.


In any event, NONE of this SHOULD be happening. You need to lean on your installer to do the necessary work to isolate this and fix it. For example, in a properly set up system, there should be no need for cheater plugs. The fact that a cheater plug is helping means there is something wrong ELSEWHERE.

--Bob
 

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Isolate electrical feeds.
 

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Quote:
Originally Posted by Bob Pariseau /forum/post/0


Ground loop interference, for example, often comes in on the feed for your cable TV -- when it hasn't been propely grounded at the point where it enters your house. This one's easy to spot if problems go away the moment you disconnect the cable TV feed from the back of your cable TV receiver.

--Bob

Boy that's a big 10-4. Lots of older homes don't have true grounded outlets even though they are 3 pronged. I learned this the hard way when disconnecting the coax from the back of my Dish receiver. My equipment wasn't truly grounded while the coax from the dish was. I was draped over my Monster Power 3500 and as soon as I had the coax unscrewed ZAAAPP! For the record, the ground LED on the front panel of the Monster was never lit. I have since moved and have proper power, LED is now on.


To test grounding, go to Ace Hardware, Lowe's or someplace and get an outlet tester. It's a small yellow plug, like a normal 3-pronged plug with 3 lights on one end. Plug this in and the lights light up in different patterns according to the problems with that outlet. Really easy to use and cheap too. Ideal makes them.
 

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Discussion Starter · #7 ·
Thanks so much for the advice. I will try one of those outlet testers. Should I put the subwoofer or receiver on a different electrcial outlet?


I disconnected the coax from the back of the cable box and then switched the video on on the receiver...still getting those random white horizontal lines...Even the receiver's menu/setup screen has the same issues...


I guess that is another reason we're stumped. The home is only 1 year old. The surround sound was pre-wired and we just hooked up the home theater syytem, all new components, etc., this week. The weird thing is, other than the subwoofer making noise when we turn on the fireplace, ceiling fan, etc., the audio sounds great...no humming noise. When we view the dvd player, regular cable, etc., the audio through the receiver is great. But when we view the video from components hooked up directly through the receiver, we get horizontal white lines that randomly flicker on the screen. The tv image even flickers/bounces slightly. We're just so deflated and afraid this type of issue will never really be solved by the installer?...Thanks again all...
 

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Discussion Starter · #8 ·
Does anyone know if we can solve thes issues?....we get white random horizontal lines shooting across the tv picture when we have the audio going through the receiver...also, our subwoofer makes a noise when we turn on or off our ceiling fan speed switch or gas fireplace (uses electronic ignition)...please help...Thanks!
 

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Sure you can solve them! It just takes time to go through things in a logical fashion.


First tackle your video problem because solving it may simplify solving the audio interference.


The first thing you need to do is verify your receiver is not faulty.


That means disconnecting it from EVERYTHING. Then take it into a different location so that it is on different power -- perhaps back to the store where you bought it. If your receiver has a procedure for resetting it to Factory Default settings, write down your real settings and do that.


You will also need a source device and a TV. Again this might be easiest in the store. Just hook up video in and out and see if you get a clean video signal. You will have no audio of course because you don't have any speakers connected.


Now add audio from that source and a pair of front speakers. Everything still OK?


If not, your receiver needs service.


If all is OK, then bring the receiver back to your home theater. Hook up (1) JUST your DVD player for audio and video, (2) one style (only) of video connection to your display, and (3) wires to your front speakers. The DVD player, display, and speakers should have no other connections to ANYTHING ELSE.


Leaving the fan and fireplace off so that they are not an issue, do you get clean video and audio?


If not, you now have a simpler set of things that could be causing the problem -- cables or your particular DVD player, or display.


If so, start adding things back in, hooked through the receiver, until you find the point at which the video goes bad.


Once you know which combination of devices is causing the problem you can start trying to figure out why.


--------------------------------------------------------------------


Once you've solved your video problem, you can tackle that audio interference. That will likely need an electrician. You need to make sure the sparker and fan are PROPERLY grounded. You may also need to have a separate power circuit run for them or for the rest of your home theater stuff.

--Bob
 

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Discussion Starter · #10 ·
Bob,


I will try and lean on the installer to do this. I just don't know how much time they will spend on this before they say it's an electrical wiring/homebuilder issue or a faulty receiver issue.


I purchased an electrical outlet tester as suggested, and all the outlets seemed to be ok, including the fireplace and outlet where the powered sub is plugged in. However, I was not able to test the outlet or power strip where the home theater components are plugged in because it's located behind the tv and I can't do this by myself.


Hopefully, the installer will follow your advice...


Thanks
 

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The interference from turning on equipment means that the power supplies in your amplifier/s aren't isolating enough. Turning on and off load, such as an igniter, or a heavy inductive load like a ceiling fan, will cause distortion to travel through the power line, back to your amp.


First, try to move the amp to another circuit, if possible. If that's not possible, or if you still have the pops (traveling all the way back through the sub panel), then you need a power conditioner before your amp/s. The ideal solution would be to get an online UPS (you can find these for sensitive medical equipment, for example). This works by taking in power, charging a battery, then using that battery continually for driving a power inverter that generates the power sine wave for the output. Note that this is different (and harder to get) than a typical off-line UPS that you'd use for a computer.


You can also try filtering power conditioners, although they typically get expensive when they're steep enough to actually do any good.
 

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Discussion Starter · #12 ·
Thanks so much for your response. Would this resolve the horizontal random white lines which flicker on the tv screen and cause the picture to "shake/bounce?" This only happens when viewing video which is run directly through the receiver as opposed to going through the TV. When the dvd player is hooked up ot the tv for video and the receiver for audio, everything is OK...


Thanks,
 
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