I need help with a hum in my system

I recently switched my entire system over to my new A/V receiver as part of my multichannel upgrade, but I get a hum throughout the system whenever I hook up anything having to do with the TV, i.e. the VCR, satellite receiver etc. The DVD-A player which is not hooked up directly to the TV causes no problems. The funny thing is, the hum is almost non existent on the connections for the CD/SACD player, on everything else, even where there is nothing hooked up, the hum is insanely loud, and is loudest on the multichannel 1 input.

Any thoughts anyone?

 

Yeah, I guess I did ask for it, but a fooey to you anyway.

 

Sounds to me like you need a cable shunt (filter) for your cablevision where it attaches to whatever you have it plugged into. They are available at Radio Shack for about $10.00. I used to have the same problem while listening to FM via cablevision.

 

Do you mean a RF interference filter?

 

You probably have a ground loop through your cable TV feed which is very common. The easiest way to test this is to hook up everything so you get the hum your talking about. Then simply disconnect the cable TV feed that goes into your VCR or TV. If the hum goes away then its a cable TV ground loop issue and its easy to fix. Radio Shack sells a little module with F-connectors designed to increase the inductance to ground to reduce the effect of the ground loop. They may be called RF filters, I'm not sure. The product description says it will eliminate induced hum or ground loops because that is how I decided to get mine. They work.

John

 

Yes, that's what I mean GB.

 

Well, I've checked the Radio Shack website and they have two products that fit your suggestions, one is an RF interference filter like Dave suggests and the other is what John recommends, which says it will eliminate hums etc. Oh , what to do, what to do? I guess since they are both very inexpensive, it wouldn't hurt to try/use them both.

 

Hi GoldenBoy,

If that doesn't do the trick and ya wanna up the ante ya may wanna try one of these:

http://shop.polkaudio.com/customer/product.php?productid=38&cat=6&page=1

Probably cheaper somewhere else, but I don't know where.

-Jeffrey

 

Try this article at the psaudio website http://www.psaudio.com/articles/hum.asp
They also have a "humbusters" section that you can get to if you register at the site (free)

Jay N.

 

Thank you all for your help and suggestions, I truly appreciate it.

Jeffrey,

I think I will try that unit from Polk, it looks good.

Ted,

Thanks for the link to the article. It has helped me confirm that it is in fact the satellite connection that is causing the hum in my system. I'll give the the unit from Polk a shot and hopefully that'll be the end of it.

 

One more thing. Since I have a connection from an antenna going to my VCR and a connection from the satellite dish going to my DirecTV receiver, I have discovered that the hum is being caused by both connections. I do get my local channels through DirecTV now, which wasn't always available, hence the antenna on the roof) but since I still need the connection from the antenna to watch one thing on the dish and tape another on local TV, I guess I'll have to put out the extra cash to take care of the problem for both .

 

Hi, Golden Boy:

I had a similar problem recently when Time Warner installed digital cable.

The Solution was to plug all components including the cable to a TrippLite Isobar 6 DBS protector into a single outlet. The TL also provides connections for satellite systems. BTW, this unit is very well built with aluminum housing and isolated filter banks.

The result was a dead quiet system. In addition, I noticed no change in the performance of my amp compared to it being directly plugged to the wall outlet.

Check it out here: http://www.tripplite.com/products/product.cfm?productID=109. I purchased the unit from dell.com for under $60.00 shipped, with one of their frequent promotions.

Regards,

Jet

 

Well, I noticed that the product from Polk clearly states 'Not for use with digital cable connections'. Well, I don't have digital cable, but DirecTV is a digital service and the signal coming down the cable for the dish to the receiver is a digital signal, so I'm assuming that the same would apply. Maybe I will try Jetsons' suggested product. I'm just glad I noticed the disclaimer from Polk before I plunked down $100 for 2 of those things.

 

It's the practice of satellite installers to ground their EQ directly to a cold water pipe.

You could try and ground your antenna mast to the same pipes.

Or, you might try and change locations for the DirecTV ground. At least see if the hum disappears when you disconnect the ground wire from the pipe.

Then you can relocate it to a spot where it doesn't cause a ground loop.

Worth a shot before spending cash on something.

 

Hi GoldenBoy,

The Polk customer service people are extremely friendly and knowledgeable. Maybe you should give them a call to see if this product will work or if they have another suggestion for you.

-Jeffrey

 

Good idea Jeffrey, I think I will.

 

G-Boy,
My advice would be to try and spend some time trying to determine exactly what the problem is. I can tell you what to do to find out if it is a ground loop.

Understanding how you get a ground loop might be helpful to you. A ground loop is caused when your system sees ground (ie. the physical connections) via more that one path. The classic cable/sat TV ground loop is when your sat signal cable is grounded somewhere near the point it enters the house and another component (anything with a three prong plug) is grounded into the outlet near your A/V system. Lets use the A/V receiver as the three-pronged compnent. Because all the interconnecting cables amonst the various compnents electrically hook all the chassis together, every component in your system can now see ground through both the sat cable and via the A/V receiver ground plug. In that case you have a ground loop and there is the potential to pick up induced currents theat can be audible.

A ground loop sounds like a low frequency hum.


Now we can say a few things.

1. I you have no three pronged plugs on any of your components then you can't have a ground loop. Its something else.

2. Take all your components with 3-prong plugs and temporarily lift the ground using a cheater plug (3-prong to 2-prong adapters). If the hum goes away then for sure you have a ground loop.

John

 

John,

Thanks for your input. I did in the past experience this same problem with my pre-amp and power-amp. It would generate a hum throughout the system whenever I connected the satellite receiver or VCR to the pre-amp. It was fixed when I did like you suggest above and put the cheater plug on the power-amp.

Now, on to my current setup. As far as I can tell, there are no components using 3-pronged plugs, but the hum is very much there. I have tested it out, and it only appears when I hook up either VCR or the satellite or both to the A/V receiver and the cable from the dish and/or the antenna are connected. If I disconnect both the sat cable from the sat receiver and the antenna cable from the VCR, the hum disappears.

 

A correction: I'm a big idiot. Contrary to what I stated above, one of my components does use a three pronged plug - my turntable. I double checked everything again and realised this. I then put a cheater plug on it and plugged it back in and then connected the audio outs from the sat receiver to the A/V receiver. After giving it a listen with the sat receiver connected and disconnected, I have determined that the hum is still present, but at a much lower level than before. So, even with the cheater plug on the TT, I still have a problem. That unit from TrippLite that Jetsons suggested is looking more and more like the way to go for me.

 

G-boy,

The fact that the hum gets reduced with the cheater plug has got me a little worried, you may have a combination of problems.

One more question. If the turntable is completely unplugged do you hear the hum? I would assume yes.

I think you are following the correct path though. Get rid of the hum with the turntable unplugged first, then see if anything happens when you plug your table back in.

John

 

So you think that the TT is part of the problem too? I can completely eliminate the hum with the TT plugged in by disconnecting the antenna and dish, but with them connected the hum does reduce somewhat with the TT plugged through a cheater plug. Again though, with the TT plugged in, cheater or none, there is no hum unless the antenna and dish are connected to the TV or VCR respectively.

BTW, just in case you or anyone was wondering, I do have the TT grounded on the receiver.

 

You could check this site http://www.jensen-transformers.com/ for info on cable TV induced hum. Jensen transformers are a little pricey, but I think the TV source is the source of the hum, so concentrate on filtering that signal. If the Radio-Shack filter works and is cheap, go with it.

There are some discussions on hum and buzz in the Audio Hardware archives.

 

I agree with cwon as I myself was told by an audiophile dealer that the Radio Shack is just as good as the Polk but 1/20th the cost and mine is still fuctioning perfectly after 4 years.

 

Thanks cwon, I'll take a look. You guys are all so really helpful.