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mvmanolov
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Musical Fidelity M3si 60Hz Hum

Hi all, here is a bit of an oddity that i am struggling with.

I have a MF M3si connected to a part of Monitor Audio Silver 8 towers. The amp is feb by a mac mini via USB.

I hear a constant 60Hz hum from the speakers at all times (independent from volume setting). No matter if anything is connected to the AMP or not, no matter which outlet the AMP is plugged into, and no matter if the AMP is plugged in directly or via a ground lift. I have also tried two different high quality power conditioners, with no effect. And 4 different power cables, again pretty hight quality, with again no effect.

I know that it isn't the AMP because at my dealer's there is no hum.

Its also not cross-talk because the speaker cables do not come even close to any other cables.

And, I also get the same hum from another integrated AMP I tried, and older Arcam unit, which makes me think that its not the MF.

At this point I am at a complete loss as to what it may be.

Any and all ideas are welcome. Please.

Cheers,

commsysman
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Joined: Apr 4 2006 - 11:33am
Bum Hum
mvmanolov wrote:

Hi all, here is a bit of an oddity that i am struggling with.

I know that it isn't the AMP because at my dealer's there is no hum.

And, I also get the same hum from another integrated AMP I tried, and older Arcam unit, which makes me think that its not the MF.

Cheers,

You get the same hum from another integrated amp. That certainly lets out the MF amp.

The amp power supplies should have no problem filtering out any 60 Hz from the power line, unless they both have defective power supplies. No hum at your dealer lets that out anyway.

It seems to me that the only way this can happen is if the amplifier is situated next to a powerful source of a 60 Hz magnetic field. It could be another piece of equipment that is situated nearby, or perhaps some sort of lighting that is radiating. Is there any fluorescent lighting in the room. Fluorescent lighting can radiate a large amount of 60 Hz or 120 Hz crap, which could be picked up by circuits. Other types of lighting can also be guilty.

Try turning off all nearby lighting.

Also, could there be a large electrical device in or on the other side of a
nearby wall?

Grounding the metal chassis of the amp with a 16 gauge or larger wire might be something to try. Also, make sure that the ground pin of your electrical outlets is actually connected to a ground bus in the power panel, which should be connected to a large ground rod or metal plumbing for a true earth ground.

mvmanolov
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commsysman wrote:
commsysman wrote:
mvmanolov wrote:

Hi all, here is a bit of an oddity that i am struggling with.

I know that it isn't the AMP because at my dealer's there is no hum.

And, I also get the same hum from another integrated AMP I tried, and older Arcam unit, which makes me think that its not the MF.

Cheers,

You get the same hum from another integrated amp. That certainly lets out the MF amp.

The amp power supplies should have no problem filtering out any 60 Hz from the power line, unless they both have defective power supplies. No hum at your dealer lets that out anyway.

It seems to me that the only way this can happen is if the amplifier is situated next to a powerful source of a 60 Hz magnetic field. It could be another piece of equipment that is situated nearby, or perhaps some sort of lighting that is radiating. Is there any fluorescent lighting in the room. Fluorescent lighting can radiate a large amount of 60 Hz or 120 Hz crap, which could be picked up by circuits. Other types of lighting can also be guilty.

Try turning off all nearby lighting.

Also, could there be a large electrical device in or on the other side of a
nearby wall?

Grounding the metal chassis of the amp with a 16 gauge or larger wire might be something to try. Also, make sure that the ground pin of your electrical outlets is actually connected to a ground bus in the power panel, which should be connected to a large ground rod or metal plumbing for a true earth ground.

Thank you for this Commsysman.

I actually just tried the following: I turned off all breakers on my panel except for one which feeds a couple of outlets that are not used, no lights or any other electrical devices are connected to these. When I pugged in the MF to one of these there was still hum coming through the speakers, but it seemed slightly less loud (though I can't be 100% sure).

As to the wall, it is an outside wall. But I am in a row-home (townhouse) and I am the end unit, and on precisely that outside wall, I would say about 10ft away are located all the electrical meters for the rest of the homes (6 homes in total). In addition the mains transformer is located just across the street, so my house is about 100ft away from it, and I'm assuming that this is where we get our electrical supply from.

In other words, could it be that all that noise is coming from outside the home? And if so, what are my options (aside of buying a new house of course).

As to the ground, I have not yet explored this further. I do have a 16awg wire connected to the water main and to the panel, and as far as I know (though I will check this also) all the wiring in the house is grounded in the panel to this main ground.

You suggested that I ground the chassis. How would I go about doing that? There is a separate grounding pole on the MF, but I think this is connected to the phono stage.

Thank you again for all of your help.
I truly appreciate it.

Best regards,
Martin

mvmanolov
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Update

I also just checked the grounding on the outlets and everything seems fine, ground is properly connected to the box and receptacle.

commsysman
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HUMMMMMM
mvmanolov][quote=commsysman][quote=mvmanolov wrote:

Hi all, here is a bit of an oddity that i am struggling with.

As to the wall, it is an outside wall. But I am in a row-home (townhouse) and I am the end unit, and on precisely that outside wall, I would say about 10ft away are located all the electrical meters for the rest of the homes (6 homes in total). In addition the mains transformer is located just across the street, so my house is about 100ft away from it, and I'm assuming that this is where we get our electrical supply from.

Thank you again for all of your help.
I truly appreciate it.

Best regards,
Martin

It sounds like you have the answer to your problem. Those electrical meters have high-current 200 volt wiring going to and from them , so you are dealing with a very strong electrical field that your equipment is immersed in.

In my opinion, the only solution is to get your audio sources and amplifier as far from those meters as possible. The speakers could be located on that wall, however, because the speakers and their wires are not particularly susceptible to this type of field.

In any case, find some way to relocate your equipment, and if you have to run long speaker wires make sure that you use 14 gauge wire (not 16 or 18 gauge or smaller). You can get pure copper 14 gauge speaker wire from Monoprice for very low prices, and it is excellent.

commsysman
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SPEAKER WIRE

BE AWARE!

The Monoprice #14917 is NOT NOT pure copper; it is copper-clad aluminum (CCA), which is absolute CRAP!

The Monoprice #2791 IS PURE COPPER and that is what you want!

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