haireez
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Post by haireez on Apr 23, 2018 7:24:43 GMT -5
Hi,
Need some help here. I notice some quite loud noise coming from my center channel. It's running from my Magnet power amp to my Marantz 7702Mk2 processor.
I test on other channel using Magnet power amp and the noise can still be heard from other speaker. Therefore, I decided to send the amp for repair. However, the repair guy mentioned that there are some loose solder and it's been soldered to eliminate the noise.
Then I test at the repair shop and truly enough, there's no noise coming from the power amp. I took back the power amp and hook up my system and unfortunately, the noise is still present.
I believed that it could be that I did not do a ground loop. Can anyone help me how to troubleshoot to eliminate the noise? How do you do the ground loop from my Marantz and why only Magnet power amp have this issue and not on my rotel 6 channel amp?
Any help would be greatly appreciated.
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Post by barclay66 on Apr 24, 2018 6:19:38 GMT -5
Hi,
First question: Did it work without the noise at some point or is it that it has been there always?
Second question: If the noise appeared at some moment, did You change anything in Your setup and what?
Third question: Is the earth connector of the Magnet amp connected to the outer contact of its chinch plugs?
Fourth question: Is the earth connector of the Marantz processor connected to the outer contact of its chinch plugs?
I want to get a clear picture of the problem first...
Regards
barclay66
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haireez
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Posts: 68
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Post by haireez on Apr 24, 2018 10:12:13 GMT -5
Hi Barclay,
Question 1: there is slight noise initially but after my 2 weeks UK trip, the sound was too loud that you cannot listen to your home theater.
Question 2: I can't recalled changing anything before my trip to UK. When I turn on my system, the noise on the center channel was too loud to watch any movie.
Question 3: really not sure what you mean by this. Is there a simpler way for me to confirm?
Question 4: I will take picture of the Marantz back panel and will post the picture soon.
Thanks Barclay
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haireez
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Posts: 68
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Post by haireez on Apr 24, 2018 10:21:30 GMT -5
Should I connect wire from the signal loop for grounding? If yes, where should I ground the wire to? |
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Post by barclay66 on Apr 24, 2018 14:20:49 GMT -5
Hi,
Regarding the third question: With a multimeter set to continuity check (or set to ohms measurement if there’s no continuity check option), measure for continuity between the metal outer ring of any cinch connector and the earth contact of the power plug (the longer one in the middle). That should tell You if signal ground is connected to earth potential or not of either device.
That ground screw terminal usually is only used for turntables which have an additional ground wire.
With ground loops there usually are only two options: Either separate the ground potentials using isolation transformers or similar technologies (using optical connections work too) or force both devices onto the same potential by connecting both signal grounds to the same grounding point via thick wires. There should be a lot information on the web. Try searching for ‘eliminate ground loop’ or similar.
Another two questions:
Are processor an amp connected to the same wall plug? If not, try it out.
Can You try a different amp for the center channel? That would eliminate a possible problem with the center preamp output...
Kind Regards,
barclay66
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haireez
Unmoderated Off Topic
Posts: 68
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Post by haireez on Apr 29, 2018 5:01:57 GMT -5
Hi Barclay,
I used a multimeter and there is a continuity between the cinch and the earth contact of the power plug in the middle.
I do use a Shuyanta powerconditioner on same filter for my Marantz and the power amp.
When using another power amp, the center channel does not exhibit any noise.
I did a clean up on the power point plug and re-organise again.
Tried connecting and 'ON'my power amp again. This time the noise is gone when I change the balance cable (preamp is balanced while power amp is RCA connector) .
However another problem surfaces:
1. The noise only came when I turn off the power amp and the noise start to be heard from the center channel again. Weird and I quickly pull out the RCA cable to prevent noise coming from my power amp.
2. When I tried to connect a HDMI cable from my cable TV, the center channel exhibit noise again. Not too sure why?
Do take note that I notice the Marantz power connector is 2 prong instead of 3. Not too sure if this is part of the issue that I face. Been using the processor for more than 4 months now and no issue initially.
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Post by barclay66 on Apr 30, 2018 4:14:29 GMT -5
Hi,
Mixing balanced and unbalanced signals often creates problems. I assume that the processor's output is a XLR socket, correct?
And the amp only has an RCA (cinch), correct? You culd check the adapter cable that You use for connecting them. It should be built like this:
What is the noise from the center channel like? Is it a humming, hissing or crackling noise?
Kind Regards, barclay66 |
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haireez
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Post by haireez on May 3, 2018 5:05:15 GMT -5
Yes. However, the processor also have RCA connection which I'm using right now. During movie time, the crackling noise is gone but when you turn off the amplifier, you can start hearing the crackling noise for maybe 10econds. It is as though as there is some energy discharge from the amplifier.
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Post by barclay66 on May 7, 2018 6:37:20 GMT -5
This is indeed strange. I would suggest adding a separate grounding wire. On the device shown in the picture above You could use the grounding screw. On the other device, You could use one of the screws that hold the metal case together.
Kind Regards,
barclay66
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