marantz av7005 hum noise - AVS Forum
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post #1 of 8 Old 03-04-2012, 01:22 PM - Thread Starter
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everything that is hooked up in the current setup:

computer:
mac mini connected to av7005 via HDMI

storage:
mediasonic hf2-su2s2
plugged into the macmini via USB.
(problem 1(but very minimal): when the drive seeks you can hear it on the speakers, I believe this to be because of the ****** on board sound card in the mini)

preamp
marantz av7005

fronts
yorkville nx55p (connected via XLR)

subs
yorkville ls2100p(connected via XLR, plugged into a surge protector on the other side of the room)
2x12" MTX terminators with a sony car amp which im powering with a computer PSU(connected via RCA)

Other devices:
xbox 360 (hdmi)
wii (directly into the TV, component)

power
Belkin PF30 - receiver, nx55ps, mini, tv, mixer(not in use) - everything else is plugged into a surge protector which goes into the wall.

cable box
explorer 3250hd

TV
LG 60" plasma (dont have the model # on hand)


up until this point everything is fine except when the USB storage seeks files i can hear it.

I then tried to connect my KRK rokit 8's into the surround L & R XLR outputs on the marantz and as soon as i do this the yorkville speakers buzz/hum?(power plugged in on opposite side of the room) It doesn't happen until the power is connected to the rokit 8's.

I have tried differen't XLR cables without any change, and tried different outlets with the studio monitors. also tried plugging one directly into the belkin pf30 with no change. Tried XLR to RCA and RCA to RCA cable and it lowers the noise but doesn't remove it.

The nx55p have a cut off button which changes it from 60hz to 100hz, when i turn it on a bunch of the noise is reduced.

I've tried the usb storage which causes the other noise but there is no change.

I've also tried disconnecting the subwoofers and no change.

The house is very old, can't think of anything else to add I'm sure there are a few other things I've tried but don't remember now


edit: removing the nx55p's when the rokit 8's are connected removes "some" of the noise but the rokits on their own still create hum

disconnecting the cable box hdmi from the av7005 removes some hum.
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post #2 of 8 Old 03-04-2012, 01:40 PM
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Wigging the cables listen for changes in hum
Move the hardware, magnetic fields
Do a 180 with the power cords, one at a time. you will need to make a cheater
I used a 3 to 2 prong adapter and filed down the fat side.
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post #3 of 8 Old 03-04-2012, 02:05 PM - Thread Starter
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so it seems most of the noise is coming from the cable line that plugs into the digital box.

however there is still a noise over the nx55p's with the rokits plugged in, i would describe it more of a buzz than anything else

what also puzzles me is why does the cable line only cause noise when the studio monitors are plugged in?
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post #4 of 8 Old 03-04-2012, 02:27 PM
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99% of the time, hum, buzz or whatever is due to wiring and hardware placement. The next step is the hardware has a issue and may need service.
It maybe the gains are set to high. Check the manuals for setup tips.
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post #5 of 8 Old 03-05-2012, 09:53 AM - Thread Starter
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cable box doesn't buzz if monitors are not plugged in.

monitors dont create noise if they are connected via RCA(preamp) to XLR(monitor) and if they are plugged into the same power outlet as the preamp.

XLR to XLR causes buzz, all the cables work fine on their own.
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post #6 of 8 Old 03-05-2012, 12:40 PM
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Quote:
Originally Posted by icecold2021 View Post

so it seems most of the noise is coming from the cable line that plugs into the digital box.

however there is still a noise over the nx55p's with the rokits plugged in, i would describe it more of a buzz than anything else

what also puzzles me is why does the cable line only cause noise when the studio monitors are plugged in?

because it completes the ground loop...

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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 #7 of 8 Old 03-05-2012, 02:25 PM
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Ground loop problems are usually caused by cable TV. I had one recently, it was 90% cured by using an isolator for the cable input (I had a surge suppressor with one). A 3 prong to 2 prong cheater plug fixed the rest.
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post #8 of 8 Old 03-19-2012, 05:46 PM
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Quote:
Originally Posted by icecold2021 View Post

...
I then tried to connect my KRK rokit 8's into the surround L & R XLR outputs on the marantz and as soon as i do this the yorkville speakers buzz/hum?(power plugged in on opposite side of the room) It doesn't happen until the power is connected to the rokit 8's.

I have tried differen't XLR cables without any change, and tried different outlets with the studio monitors. also tried plugging one directly into the belkin pf30 with no change. Tried XLR to RCA and RCA to RCA cable and it lowers the noise but doesn't remove it....

Not sure if this is related but wanted to post something as I was dealing with a similar situation.

I run a record label and have the following setup in the studio:

Yamaha RX-V867BL 7.2-Channel and using it as a preamp
KRK Rokit 8 (Fronts)
KRK Rokit 8 (Center Channel)
Fostex PM0.4 (x4) (Rear)

I was getting a hum with the Rokits as well. It was driving me crazy as I tried using different ac outlets, power cords, 1/4 inch and XLR cables. Nothing seemed to work until I ran this in between the monitors and receiver:

Ebtech HE-8 Hum Eliminator 8-Channel Single Space Rack


They also make in for XLR: Ebtech Hum Eliminator (8 Channel XLR)


Once I got that hooked up the hum was gone...completely.
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