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Hum/Buzz is back.....

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I've exhausted my thoughts and efforts in eliminating the buzz/hum I'm getting. I had DirecTV installed about 2 months ago and have been getting a hum through the speakers when the Pre amp and amp are one. When they are off the buzz does not come through the TV speakers, only the HT speakers. I've unplugged all components individually to narrow it down. What I've come up with is the the DirecTV coax lines are cause the interence. The hum which is excessively loud (70 dB's) happens even when the power is removed from the DirecTV box and only disappears when the coax lines are removed from the DirecTV box. I've managed to get the hum down to a minimum by running it through the surge protector. any thoughts and Ideas would be greatly appreciated.

I've got 1 APC H10 and 1 APC H15, the amp, pre amp and sub are plugged into the H15 and the rest is plugged into the H10 (TV, XBOX 360, CD player etc.). The H15 and H10 are plugged into the same wall outlet.

I don't think it's a ground loop, I've looked all over the house for other potential grounds and still only find the Main Ground. It could be some Major RFI getting into the lines, if so how do I shield the cable from it?

I've got a Tech comming out sunday to see if there's bad connections or a bad grounding block. Hopefully they'll send someone knoweledgable . I'd still however appreciate any input from you ladies and gentleman in resolving the issue.

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disconnect all your signal cables and plug them back in, one system at a time ( no power when connecting, aye!?! )... lots a work, but worth it. If you discover the device causing the problem, plug THAT device into a grounding adapter without attaching the gound connection ... someboby is sure to speakup about this NOT being correct, but IGNORE. Once you determine the source of your hum, update the thread. It could be as simple as connection corrosion or bad cables.

Good Luck

j

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I don't think it's a ground loop, I've
looked all over the house for other potential grounds and still only
find the Main Ground. It could be some Major RFI getting into the
lines, if so how do I shield the cable from it?




Why do you think that? What you're describing sounds exactly like a text book example of a ground loop to me.




I've
not tried this myself, but Bhendrix has had good results shorting the
shield of the coax to the chassis of his audio gear (or something
similar)....so basically shorting the coax ground to the house ground.




Another alternative is adding galvonic isolation to the
DirectTV coax - so basically a transformer, which that link to parts
express is a good example of. However, you gotta be careful that the
transformer maintains a proper impedance and doesn't start rolling off
the highs...I would try the parts express device, but if you notice
certain channels not working, then you'll have to look into one of the
more expensive options (which are using better transformers).




What's
happening is that your coax ground is at a different potential than
your house ground and your audio ground is coupling to the coax ground
through the chassis of your gear. At least one of your pieces of audio
gear has gotta have a 3-prong plug on it - lifting that prong should
get rid of the hum, but then you're removing the safety feature of that
3rd prong, which I don't recommend unless you've got it plugged into a
GFCI outlet (the ones with the little test and reset buttons on them).

The purpose of the 3rd prong is to provide a safe path for enough
current to travel and trip your house's circuit breaker in the event of
an internal failure that results in the chassis going live. It
basically prevents the user from becomming that path when the gear is
touched. It also prevents a brown out failure from catching the wires
inside the walls on fire. A GFCI compares the current between the
Neutral and Positive and will trigger anytime the current going into
your device is more than the current going out - so effectively
accomplishing the same thing.

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I assume that all components are pluged into the same outlet/power strip. Multiple wall outlets are begging for trouble. I had exactly the same 70 Db hum that you are describing. The addition of 2 monoblocs triggered the noise. Note- my direct TV dish is attached to a steel pole mounted into the ground. I had a slight hum with mine when it was mounted to a wooden fence but nothing like you are describing. Sure as heck sounds like a ground loop. Double check that the cable is not touching or near any amp transformers or crossing any other wires- if possible..The culprit in my situation was a Monster strip that I was using for an extention cord to reach some components. I carefully moved all wires away from the amps and switched power strips. Problem gone. Mine drove me crazy for 3 days until I fixed it.

I am just throwing out some ideas. It is my understanding that some of the most insignifigant little things imaginable can cause these problems.

Hope you find the problem. real PITA.

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Could you take a multimeter with freq. capability and measure a hum like this at the speaker wires? If I had a hum, I would try it and I suspect the hum would be at 60hz.

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Got rid of the buzz by using the cheater plug. That eliminated the rest of my hum.buzz problem.

Now my question is since I've bypassed the safety mechanism should I ground the cheater plug to the grounding lug on the APC unit?

I think the amp is far enough down the surge protection line that it will be fine, the amp is pluged into a Mondial RPC 120 switched outlet the is plugged into the APC H15 power conditioner and it's plugged into the wall.

I don't have a Multimeter. Should I still have the DirecTV guys come out and look at the coaxial lines if they are the ones that introduce the buzz or is it something on my side that needs looked at?

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I don't think you can put a transformer in the DirecTV line(s) going to the dish.

I believe there is a DC voltage present on the line, generated by the box and used to tune

the downconverter on the dish.

A transformer will not pass DC.

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Got rid of the buzz by using the cheater plug. That eliminated the rest of my hum.buzz problem.

[:o]

I have exactly the same problem attaching my HP Pavillion to the TV/stereo (the S-Video cable connection causes audio buzz like the dickens). You DO have a ground loop... fixing hasn't always been that easy for me.

I "live" with an ungrounded connection to the laptop adapter ... but I am willing to take the risk ... so I can't reccommend this 'solution' for everyone.

[;)]

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You know what I just discovered, is that if I switch my playback type from my ps3, I get tremendous mum and buzz. but If I keep it off 7.1 my system is very very quite.

not sure if this helps... but I didnt notice this about playbeack choices just this weekend

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Guest " "

can you put the direct TV box on an optical connection to your audio gear? The optical connection won't transmitt the hum/buzz.

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can you put the direct TV box on an optical connection to your audio gear? The optical connection won't transmitt the hum/buzz.

it is connected via optical, the buzz would stay constant even through HDMI, component video. Eliminating the ground plug fixed the problem

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