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Old 28th November 2007, 08:59 AM   #1
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Default Humming

Hi!

I just have bought an old ELECTROCOMPANIET AW250 power amp, which uses a 1.200Va massive toroid. Well, when connecting, appears a "hum" sited inside the amplifier, not through the speakers (mechanical humming). Well, the toroid rests directly over the chassis, as seen in the following pic:
Click the image to open in full size.

The hum within is a constant 50Hz noise, mostly negligible when listening, but if you get concentrated, the noise is there, so now it's inside my head .

Well, somebody know any grandmo trick do minimize this mechanical noise? I have heard that using a kind of hule/rubber between the toroid and the chassis could make this noise sensation ends.

Best wishes,

Jorge.
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Old 28th November 2007, 08:33 PM   #2
jaycee is offline jaycee  United Kingdom
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get a sheet of neoprene or similar and make some mounting gaskets for the transformer. You normally get such things with toroidal transformers when you buy them.
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Old 28th November 2007, 10:30 PM   #3
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Default THX!

Ok, I will go for it. Thank you very much.

Regards,
Jorge.
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Old 29th November 2007, 08:22 AM   #4
Nordic is offline Nordic  South Africa
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Q: How do I get the transformer to stop humming?

A: Teach it the words to the songs...
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Old 29th November 2007, 08:33 AM   #5
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Fantastic solution!

Regards,
Jorge.

Ps.: It's a pitty it doesn't understand Spanish (the toroid, I mean).
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Old 29th November 2007, 08:48 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
The mechanical hum could be due to mains DC passing through the toroid.
It might be worth trying a DC blocker in the primary feed. If it helps then build it into the amp.

Remember, the DC blocker will operate at mains voltage and is NOT isolated. Be very careful with both the temporary and permanent implementations.

http://sjostromaudio.com/joomla/inde...-WARNING-49575
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Old 29th November 2007, 08:58 AM   #7
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Hi, Andrew; thanks for your reply.

I think it's something within the power amp, because that hum doesn't appear in my Vincent SP-991 Plus mono power amps (each one got a 1.500Va power toroid, but fully covered to avoid humming, I think), neither in other amplifiers. Do you still think that could be caused due to DC passing through the trafo?

Thanks in advance,

Jorge.
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Old 29th November 2007, 09:39 AM   #8
AndrewT is offline AndrewT  Scotland
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Mechanical hum/vibration can be due to any resonance brought on by the mains frequency.
Some toroids seem to be tolerant of DC on the mains and others hum badly.
The clue can be that the mechanical hum varies at different times of the day when other industrial loads are on/off.
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Old 29th November 2007, 10:00 AM   #9
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Quote:
Originally posted by AndrewT
Mechanical hum/vibration can be due to any resonance brought on by the mains frequency.
Some toroids seem to be tolerant of DC on the mains and others hum badly.
The clue can be that the mechanical hum varies at different times of the day when other industrial loads are on/off.
It is said that toroids don't use to be noisy, but reality, sometimes, says the opposite.

I was said that depending on the time of the day, the humming can volume up or down, but I just listen the same 50Hz desgasting noise up there. Maybe by isolating the toroid using silicon?

I really don't know what to do, but the only things I think that can end up the problem are or a silent toroid change or by isolating the toroid from the chassis. What do you think about?
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Old 29th November 2007, 10:23 AM   #10
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In this link you'll see a thread when I opened my amplifier up. As you see, the toroid is placed directly over the chassis. Do you know someone with the new model, the ECI 250-R with such a noisy humming? toroid's position is about the same.

http://www.mundohi-fi.com/forum/view...r=asc&start=10

Regards,

Jorge.
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