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House grounding problems : noise from speakers, fix? - Page 2

post #16 of 28
11/21/09 at 3:41pm
Thread Starter 
I don't believe in carpal punishment..

:] No response to spanking, buzzes on without crackling. I heard one more person report the same thing on the internet so I don't think it's common, sounds like a manufacturing defect. What would I check in this kind of issues? soldering shorts?

Or perhaps this is specific to location; I see radio towers out of my window, but that's only active for emergency broadcasts.
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post #17 of 28
11/21/09 at 4:45pm
Quote:
Originally Posted by AudioNoob View Post
I don't believe in carpal punishment..
Ha! Great retort!

Quote:
No response to spanking, buzzes on without crackling. I heard one more person report the same thing on the internet so I don't think it's common, sounds like a manufacturing defect. What would I check in this kind of issues? soldering shorts?
More like a marginal or cold solder joint. AM radio signals can be demodulated by passing through a non-linear element, such as a diode junction and cold or marginal solder joints can act as a diode junction and demodulate AM radio signals.

Quote:
Or perhaps this is specific to location; I see radio towers out of my window, but that's only active for emergency broadcasts.
Are you able to identify the radio station in question? If so, then you can find out just where they're broadcasting from.

se
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post #18 of 28
11/21/09 at 5:01pm
Thread Starter 
Quote:
Originally Posted by Koyaan I. Sqatsi View Post

Are you able to identify the radio station in question? If so, then you can find out just where they're broadcasting from.

se
To shut them down! They have horrible taste anyway.

So how would I know a cold solder joint, do I ask knock knock? or are those the ones that sort of separate with a black line?
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post #19 of 28
11/21/09 at 6:33pm
Quote:
Originally Posted by AudioNoob View Post
To shut them down! They have horrible taste anyway.


Quote:
So how would I know a cold solder joint, do I ask knock knock? or are those the ones that sort of separate with a black line?
They can be nearly impossible to spot visually. I usually just go through and reflow everything.

se
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post #20 of 28
11/21/09 at 6:43pm
Thread Starter 
by reflow you mean just touch with an iron right? Not reflow as in the solder paste process.
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post #21 of 28
11/21/09 at 6:48pm
Quote:
Originally Posted by AudioNoob View Post
by reflow you mean just touch with an iron right? Not reflow as in the solder paste process.
Right.

se
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post #22 of 28
11/21/09 at 6:52pm
Thread Starter 
I'll grab by soldering Iron and give it a shot in a few days, is there an area of the amp that this would be more likely to happen? Parts of it are cast in hard resin, I can't really touch them.
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post #23 of 28
11/21/09 at 7:12pm
Quote:
Originally Posted by AudioNoob View Post
I'll grab by soldering Iron and give it a shot in a few days, is there an area of the amp that this would be more likely to happen? Parts of it are cast in hard resin, I can't really touch them.
Could be a number of places. And without a service manual with the board layout and schematics, it's hard to give any specific recommendations. Just hit everything you can get at and cross your fingers.

se
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post #24 of 28
11/21/09 at 10:25pm
The engineer in me says build a Faraday cage around the room
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post #25 of 28
11/22/09 at 1:07am
Thread Starter 
Holy, I just plugged in my display and ran the power cord by the speakers, the radio is loud and annoying.
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post #26 of 28
11/22/09 at 2:02am
Quote:
Originally Posted by AudioNoob View Post
Holy, I just plugged in my display and ran the power cord by the speakers, the radio is loud and annoying.
This is not a ground loop issue. A ground loop would cause a significant hum at 60Hz. The only real change would be the volume, not pitch, and ground loops don't manifest as hiss or radio.

It is possible there is some defect in your gear, but I honestly don't think so.

Radio interference can occur when using poorly shielded cables, particularly speaker cables. This is exacerbated if there are AC cables running parallel to the speaker cables (and sometimes signal cables) or coming into contact with them. If the speaker cables must be near any AC cables, try to make sure they only cross at right angles.

Moving your speakers around, closer or farther apart is a lot like holding up one of those Y shaped FM antennas and moving it around to get better reception.

Is it possible to substitute better shielded cables in for a test, to see if the interference improves/gets worse?
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post #27 of 28
11/22/09 at 4:20am
Thread Starter 
The cables are sort of hard to replace but I can give it a shot, but then why do things change when I move other cables around independent of the speaker cables?
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post #28 of 28
11/22/09 at 5:15am
Quote:
Originally Posted by AudioNoob View Post
The cables are sort of hard to replace but I can give it a shot, but then why do things change when I move other cables around independent of the speaker cables?
Seems the other cables are helping to amplify or reduce the interference, odd as it may seem. Moving them closer together or farther apart will raise and lower the antenna type action you have going on. You said that moving your body closer to the speakers also has an effect, which leads me to believe that this really is a matter of airborne interference. If you've ever used rabbit ears on a TV, you might recall that when the picture is less than stellar moving your body in relation to the antenna and TV set can have an effect.

One other possibility could be that there is a ground issue that is not a loop, but something not right in the grounding of your electrical system.

But what you are describing I have experienced before, and the problem was usually solved by uncoiling the speaker cables, moving all AC cables as far from them as possible, or when not possible, crossing them at right angles to one another, and making sure the speaker cables were properly shielded and the lengths as short as possible.

Properly shielded cables should not be this sensitive to radio interference, unless the cables are wound into a coil. When that happens, you can pick up interference without even powering up your system at all.
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