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post #1 of 8 Old 08-20-2018, 02:04 PM - Thread Starter
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Projector and Audio noise in speakers

Looking for any hints or experience/ guidance before I head home from work to start tinkering. Have a dedicated HT close to being finished. Marantz 7704 -> Monolith 7X -> Klipsch THX in walls. Speakers have been installed and Audyssey calibrated...etc. Basically everything was running great. The Marantz and the Monolith are each on a separate dedicated circuit. They are connected with BlueJeans RCA's (like 6 ft).


Now last night we hang the screen and hook up a JVC DLA-X590R projector. Picture focus, zoom, shift all look awesome. First movie runs bring a tear to my eye. Finally my own HT.
However, now that the projector is plugged into the Marantz (HDMI through main out) I have a ground loop hum. Not terrible, but easily noticeable.


Marantz and JVC are on the same circuit. Both plugged into the same power filter. JVC is three prong. Marantz is two prong. The Monolith is two prong on a different 20A circuit and its own 20A power filter. Ive already tried grounding the amp to the power filter to no effect.


Obviously the issue is with the JVC being added in. I will move it to a different outlet circuit first. See if that fixes it. But all grounds lead back the panel box...so might be to no avail.

Will it make any difference to use a separate filter/protector for the projector? like plug them into the same outlet/circuit but on separate filters for the Marantz v JVC?
Can HDMI cables have issues onto themselves? can they be the culprit?

The Marantz has a ground terminal on the chassis. Worth a try. But how far should I take it, before saying it was of no help. To the panel? To the copper water main? I actually have a grounding terminal block at my panels that is to the stake outside...so yeah lots of options.

Least desirable would be to switch to XLR inter-connects.$$$ and time to order. Using RCA as I started with A Denon 3400H as the processor controller decided to upgrade due to great price of 7704.

any experience to share, or guidance is appreciated. thanks
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post #2 of 8 Old 08-20-2018, 02:19 PM
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Originally Posted by HighModulus View Post
Looking for any hints or experience/ guidance before I head home from work to start tinkering. Have a dedicated HT close to being finished. Marantz 7704 -> Monolith 7X -> Klipsch THX in walls. Speakers have been installed and Audyssey calibrated...etc. Basically everything was running great. The Marantz and the Monolith are each on a separate dedicated circuit. They are connected with BlueJeans RCA's (like 6 ft).


Now last night we hang the screen and hook up a JVC DLA-X590R projector. Picture focus, zoom, shift all look awesome. First movie runs bring a tear to my eye. Finally my own HT.
However, now that the projector is plugged into the Marantz (HDMI through main out) I have a ground loop hum. Not terrible, but easily noticeable.


Marantz and JVC are on the same circuit. Both plugged into the same power filter. JVC is three prong. Marantz is two prong. The Monolith is two prong on a different 20A circuit and its own 20A power filter. Ive already tried grounding the amp to the power filter to no effect.


Obviously the issue is with the JVC being added in. I will move it to a different outlet circuit first. See if that fixes it. But all grounds lead back the panel box...so might be to no avail.

Will it make any difference to use a separate filter/protector for the projector? like plug them into the same outlet/circuit but on separate filters for the Marantz v JVC?
Can HDMI cables have issues onto themselves? can they be the culprit?

The Marantz has a ground terminal on the chassis. Worth a try. But how far should I take it, before saying it was of no help. To the panel? To the copper water main? I actually have a grounding terminal block at my panels that is to the stake outside...so yeah lots of options.

Least desirable would be to switch to XLR inter-connects.$$$ and time to order. Using RCA as I started with A Denon 3400H as the processor controller decided to upgrade due to great price of 7704.

any experience to share, or guidance is appreciated. thanks
HighModulus,

Even though you have the Marantz and JVC on the same circuit, you indicated that the Monolith is on a different circuit. If that is correct, its probably causing the ground loop due to mismatched voltages, etc. and the lines using the same ground.

If you have any connection between the three it can cause the issue. If there is any mismatch, it can cause a ground loop hum. Try putting all three on the same line. This may eliminate the ground loop. The ground loops are always a headache. I just finished nailing mine down and needed everything on the same 20amp line, Just different outlets on the same 20 amp wire. Hope this helps.
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post #3 of 8 Old 08-20-2018, 02:25 PM - Thread Starter
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I will try it. Easy enough to move them all onto one outlet/circuit as the outlet are all in one area.

Thanks

Would GFI outlets cause anything? Because the outlets are in an unfinished area (feeding a rack in the theater) they were required to be GFI.
And the damn ones in the theater had to be arc-fault. Talk about expensive breakers!!! good lord!
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post #4 of 8 Old 08-20-2018, 02:39 PM
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Originally Posted by HighModulus View Post
I will try it. Easy enough to move them all onto one outlet/circuit as the outlet are all in one area.

Thanks

Would GFI outlets cause anything? Because the outlets are in an unfinished area (feeding a rack in the theater) they were required to be GFI.
And the damn ones in the theater had to be arc-fault. Talk about expensive breakers!!! good lord!
The GFCI's could be an issue. I don't have any of those on my Theater 20 amp outlets and there not required. The other one's you mentioned I have never seen or heard of them and would not know why you were required to have them in the Theater. Those are also worth looking into for the culprit.

Good luck!
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post #5 of 8 Old 08-20-2018, 03:05 PM - Thread Starter
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Yeah arc-fault breakers are now required in all occupied spaces by newer electrical codes so electrician and code official say.
Apparently 2014 National Electric Code and newer require them in occupied space, meaning the theater.


Both the code official and electrician don't like them and jokingly suspect breaker manufacturers to have a hand in the code change. $4 breaker vs. $40 breaker.
But its code.
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post #6 of 8 Old 08-20-2018, 10:50 PM - Thread Starter
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Ok after playing with different connections. JVC 590 projector is the source of noise.
The HDMI connection is causing the noise/ground loop.
Plugging it into different circuit actually made it worse.
Plugging everything into the same circuit did nothing.
Switching HDMI cables and ports on projector and processor did nothing
Trying to ground the processor chassis did nothing.

I am considering starting the effort to return the projector

Now...the one thing that did work...Running the projector without a ground. Like pulling teeth, I removed the ground prong from the outlet/plug end of the detachable power cable.
Checked with two electrical engineers friends. They were not exactly giving me high fives. But both agreed it should function. Apparently I would know instantly if this was a major issue as the electronics may check for a ground and not start up, or there would be even more noise. As the image is silky smooth, operating in normal temperature range and audio is perfectly silent again...I am closing this case

Any comments on this solution?
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post #7 of 8 Old 08-22-2018, 05:03 AM
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By any chance do you have a cable TV (or DirecTV) STB connected to the pre/pro? They're a notorious source of ground loops.

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post #8 of 8 Old 08-22-2018, 06:10 AM - Thread Starter
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Yes there is a "cable box" attached via HDMI. A Cisco 7105 digital box for TV over fiber.
But it uses Wifi for connection. So coax leading to issues is out. And I have plugged and unplugged the little guy, and the Apple TV and no issues.


Watched several movies last night. sound and picture were at or beyond expectations. But due to ground loop noise it makes when installed properly, I may choose something else. Hoping that Epson announces new projectors before my return window closes.
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