# Hum from speakers??



## Hakka (Sep 10, 2006)

My system consists of a Denon 3803 receiver, Rotel RB-1070 2ch amp for the mains, Rotel RMB1075 amp for the centre and surrounds, driving B&W 600 series speakers.

Last night I noticed a hum/buzz coming from my centre and surrounds when I got close to them. The hum does not increase when the volume control is turned up, if I mute or power off the receiver it disappears completely. The main speakers that are connected to the 1070 are dead silent. I am guessing this might be caused by a ground loop. All components are plugged into the one circuit.


Any suggestions on how to deal with this?


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## norpus (Oct 11, 2006)

Hakka said:


> My system consists of a Denon 3803 receiver, Rotel RB-1070 2ch amp for the mains, Rotel RMB1075 amp for the centre and surrounds, driving B&W 600 series speakers.
> 
> Last night I noticed a hum/buzz coming from my centre and surrounds when I got close to them. The hum does not increase when the volume control is turned up, if I mute or power off the receiver it disappears completely. The main speakers that are connected to the 1070 are dead silent. I am guessing this might be caused by a ground loop. All components are plugged into the one circuit.
> 
> ...


Yep, pray for a miracle .....(I have a denon myself and with the amount of gear/wires we have in and out of them, its a nightmare)
Seriously tho, you'll need to unhook stuff completely one u nit at a time to find the offender. As you will be running unbalanced rcas like me, ground loops are easy to make and hard to find. Patience is a virtue I have been told.:hush:


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## dynamowhum (Oct 3, 2006)

Norpus out of curiousity, do you have 220 volt mains and are they grounded at the plug? I was just wondering if you could make a direct comparision from your experience over in Oz to what we have here? I guess some of it would be the same I just don't know. No offense intended just don't know.


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## Prof. (Oct 20, 2006)

Hakka said:


> My system consists of a Denon 3803 receiver, Rotel RB-1070 2ch amp for the mains, Rotel RMB1075 amp for the centre and surrounds, driving B&W 600 series speakers.
> 
> Last night I noticed a hum/buzz coming from my centre and surrounds when I got close to them. The hum does not increase when the volume control is turned up, if I mute or power off the receiver it disappears completely. The main speakers that are connected to the 1070 are dead silent. I am guessing this might be caused by a ground loop. All components are plugged into the one circuit.
> 
> ...


Hakka,

I had a similar problem with my old Pioneer receiver, only I had the hum suddenly appear in the right channel...
After exhausting every possibilty, I finally took it to the repair shop..
The problem was dry joints in the circuitry..They re-soldered them and no more hum...
This may not be your problem, but maybe worth looking at..
I don't think it's a ground loop problem if you haven't changed any of the power connections..


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## Hakka (Sep 10, 2006)

We have 240v 50hz power, the plugs have 3 pins but do not always use a ground.

The hum is not present when using the 3803 to power the centre+surrounds, only when the 3803 is connected to the RMB-1075. I f i connect the centre speaker to the RB1070 there is no hum. I only added the 1075 to my system a few weeks ago, I'm guessing its been there all along but I only noticed it a few days ago.

I cannot hear the hum when watching/listening at my normal levels, only when the system is powered up with no audio playing, so its not a huge problem, just annoys me to know its there. When I get a chance I will play around with some connections to see how it goes.


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## norpus (Oct 11, 2006)

dynamowhum said:


> Norpus out of curiousity, do you have 220 volt mains and are they grounded at the plug? I was just wondering if you could make a direct comparision from your experience over in Oz to what we have here? I guess some of it would be the same I just don't know. No offense intended just don't know.


Yes as hakka stated, 230V 50cycle 3 pin plugs, usually earthed on HT gear.
The potentials for setting up hum loops are many.
I had a speaker/amp manufacturer out here Sunday - 1st thing they wanted to get rid of was the hum loop. After 1/2hr trying stuff, we were no further progressed and gave up to do other more exciting things (like subamp testing)
If the hum is 50Hz, (or 60 in US) it will likely be a ground loop. 
Tracking it down to the one or more offending items needs patience to try all options.
starting with plugging everything into same power outlet, (filtering power did not help me), gthen detaching leads one by one until culprits found, then plugging in again the ones that do not bring hum back. This is the theory anyway - I still haven't conquered mine


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## norpus (Oct 11, 2006)

.


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## dynamowhum (Oct 3, 2006)

State side we have 2 banks for our breaker box. I understand that sometimes even if you have seperate circuits, but have both breakers on the same bank, you can have a ground loop. Hope this may help. Cheers.


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