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Amp buzzing noise, fix needed

post #1 of 10
5/26/08 at 3:02am
Thread Starter 
So this is somewhat a speaker question, but the headphones are also part of the setup, so there's my relevancy connection.

I was getting some noticeable buzz from my new speakers that after much investigation I nailed down to this: I've got the TV and the CD player hooked into the same preamp which outputs to the amp that goes to the speakers. When connected to the TV, even when set to the CD player, the preamp was putting out a loud buzzing noise through the amp.

Finally figured out that it was coming from the cable box. Coaxial cable goes into the box, and any connectors (HDMI in this case, but composite had the same result) that went into the TV routed its way through into the amp. I've moved the cable box and coaxial cable so that it's no longer intersecting with any cables or power sources, but no change. Is there any quick fix to this, besides don't use cable TV? Any sort of filter I can use?
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post #2 of 10
5/26/08 at 8:58pm
JENSEN TRANSFORMERS, INC. - ISO-MAX® Audio Isolator Products

Look at the VRD-1FF
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post #3 of 10
5/26/08 at 9:12pm
Thread Starter 
Anything cheaper than $60? That seems way too high a price.
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post #4 of 10
5/26/08 at 9:54pm
The cable coming into your house is grounded in a different physical location from your audio gear, and when you connect the two, the variance between the two grounds causes ground loop hum.

An isolator might be the only safe way to prevent the two grounds from interfering. You could try plugging all of your equipment into the same outlet/circuit, but if the cable itself is the problem, that won't help.

From the Wikipedia page about Ground loops:

Quote:
"Ground loop issues with television coaxial cable can also affect any connected audio devices such as a receiver. Even if all of the audio and video equipment in for example a home theater system is plugged into the same power outlet, and thus all share the same ground, the coaxial cable entering the TV is actually grounded at the cable company. The potential of this ground is likely to differ slightly from the potential of the house's ground, so a ground loop occurs, causing undesirable mains hum in the system's speakers.

As with audio ground loops, this problem can be solved by placing an isolation transformer on the cable-tv coax. Alternatively, one can use a surge protector that includes coax protection. If the cable is routed through the same surge protector as the 3-prong device, both will be regrounded to the surge protector."
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post #5 of 10
5/26/08 at 9:57pm
Is your TV CRT? If the noise comes from the Flyback, not much to do there, unless separating them....Here is another solution...$60.00 for two baluns connected reversed...gimme a break!!!
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post #6 of 10
5/26/08 at 10:13pm
Quote:
Originally Posted by Sovkiller View Post
Here is another solution...
Oh, wow, I didn't look at the other one... It's a simple part after all.
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post #7 of 10
5/27/08 at 12:02am
Thread Starter 
In theory that $11 one looks good, but it's not recommended for digital cable. And I've got a 1080p LCD television. The cable box (only for television, Internet connection is through DSL) was plugged into the same power bar as the audio system and the TV.

The setup in question is visible in these two links:

http://ryanmance.com/images/2008/gear/audio1.jpg
http://ryanmance.com/images/2008/gear/audio3.jpg
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post #8 of 10
5/27/08 at 12:24am
The Jensen I suggested will work with digital cable. The cheap ones won't.

It's not a back to back balun design. It is an isolation transformer designed for this purpose.

Jensen builds some of the best transformers in the world. Legendary even.
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post #9 of 10
3/20/09 at 12:59pm
I get the ground loop hum in my system as well, but I have satellite TV. But when I disconnect the coax cables from my Directv DVR (two tuners), the hum doesn't go away, so does that mean the satellite TV is not the culprit?
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post #10 of 10
3/21/09 at 3:05pm
Quote:
Originally Posted by ScoHo View Post
I get the ground loop hum in my system as well, but I have satellite TV. But when I disconnect the coax cables from my Directv DVR (two tuners), the hum doesn't go away, so does that mean the satellite TV is not the culprit?
If it's not plugged in, it's not the problem.
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