I Guess Its Called A Ground Loop Problem

rob aylestone said:
If the computer power supply is a simple fixed voltage unit with nothing clever, then try a different power supply - this won't work with a few makes like Dell, who manage to code their power supplies so the computer recognises if a different PSU is driving it, and applies different levels of nuisance treatment. If it just says 15V DC or something - then a proper DC power supply can be sourced and try it.
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Yes. Please be careful to check the polarity before you plug it in! One would hope that the laptop has built in protection against the horrible destruction that wrong polarity DC supply could cause, but better safe than sorry.

Also try to make sure that the current rating is somewhere close to the same.

You might get some mileage out of filtering the power supply. Really just a resistor and a couple capacitors could take a lot of noise out of the PSU. It's hard to specify exactly without a bit more information. Actually would be pretty easy to build a nice regulated and filtered power supply of your own if you know which end of a soldering iron to hold.

Not sure I'd bother, though. Does the battery work?
 
what do you mean by the battery work? the laptop doesn't produce a noise with battery,it only does when i plug my charger. I tried taking about my charger from laptop too but it doesn't work
 
davethangjam said:
what do you mean by the battery work? the laptop doesn't produce a noise with battery,it only does when i plug my charger. I tried taking about my charger from laptop too but it doesn't work
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Does the battery work? Like does it hold a charge? Can you run the laptop off the battery for at least a couple of hours?

I suggested earlier just running off battery for critical tasks where the noise will actually be a problem. Is this not an option for some reason?
 
yeah the battery works for around 2 hours. @BroKen_H sorry for the typing mistake. I mean,i do try taking out the charger from my laptop and run without a battery,but it doesn't work
 
This is a pretty classic earth (aka ground) loop problem.

That the Sony is quiet on battery power just about nails it. The problem is because the charger IS earthed! The monitors are also grounded (IEC power leads?) and there lies the problem, two earthed devices.

DO NOT UNDER ANY CIRCUMSTANCES REMOVE ANY MAINS WIRING EARTHS!!!

As has been said, a 1:1 line level transformer isolator box* twixt AI and monitors would surely fix the trouble but yous broke!
One possible solution is to lift the SIGNAL earths, i.e. screens on the cables to the monitors. This almost always works but can leave the system open to RFI. That can usually be fixed by connecting a 1nF capacitor twixt dissed screen and shield connection on jack or XLR. In effect you are putting BACK the earth but only at RF.

Best fix of all is to replace the charger with one that is double insulated (we call it "class 2") and does not need or indeed have an earth......Yeah! I know!...Broke!

http://www.amazon.co.uk/gp/product/...m=A3P5ROKL5A1OLE&pf_rd_r=1A7DWH90YB90JWXDD9PW

^ had a couple of those and they work surprisingly well for the money. Be ok till fortunes improve?

*NOT! A guitar DI box!

Dave.
 
yeah. the skytronic isolator looks good but they don't ship to india. will check with another website. btw what is lifting signal earths,i don't really know anything about Electric modification
 
davethangjam said:
yeah. the skytronic isolator looks good but they don't ship to india. will check with another website. btw what is lifting signal earths,i don't really know anything about Electric modification
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Bugger! Best solution is to make a couple of "stubs" to insert in the lines. Are the monitor feed cables XLR at least at the speaker end? If so, can you run to a pair of XLR male and female cable plugs and a couple of feet of two core mic cable?

In any case I shall attach a drawing soonest.
Shame you are so far away, I have all this stuff spare and you would be very welcome.

Dave.
 
There you go.
Sorry for the hurried scrawl! You don't have to fit the capacitor C1 but it can help stop RF interference. The value is very non-critical, 1000picofarads (1nF) is about right but 10times either way would not hurt. Voltage rating is completely immaterial, no volts on it!

Any questions, redraws, come back.

In cases like this I like to make up short modd' leads, XLR to XLR about a foot long. Saves having non-standard cables around. But then, as I say, I've got all the bits!

Dave.
 

Attachments

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I'm not sure if you've checked this, but I had a similar problem recently. My monitors were buzzing like some mad hornets. Turned out I had left my phantom power on my interface on. Switched it off & fixed the problem. I'd check that before going to any elaborate schemes to fix it.
 
cldyer said:
I'm not sure if you've checked this, but I had a similar problem recently. My monitors were buzzing like some mad hornets. Turned out I had left my phantom power on my interface on. Switched it off & fixed the problem. I'd check that before going to any elaborate schemes to fix it.
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Spook juice should not cause any noise under any circumstance. There is a fault somewhere in that set up.

Dave.
 
I just want to pipe up and say that a GFCI is a ground fault circuit interrupter, not an isolator. It senses fluctuations in the electricity flow between hot and neutral and trips its own internal breaker if it detects any. This is to protect people from shock and to protect faulty devices from overheating or otherwise causing trouble. Unless it has its own isolated ground, it still uses the house's normal ground (and so it won't do anything about noise).
 
davethangjam said:
i'm planning to meet up a laptop technician/electrician in a couple of weeks. i'll be testing new power supply if it works then i'll invest on it or maybe let the electrician modify the power supply. what do you guys thinks?
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Well I'm not a recording expert but I am an Electronic Technician on my day job. Your problem definitely as stated before isn't a ground loop since your laptop power supply doesn't have a 3 prong grounded plug. A ground loop is caused when you have a potential difference between the grounds that two pieces of equipment are plugged into (say an amp and a mixer, plugged into two different outlets) this could cause current to travel on the ground on the patch chord between the two pieces of equipment, creating noise. Your problem is most likely a noisy power supply. Modifying the power supply to add a ground probably won't fix your noise problem, and will void any warranty you may have on your PC or power supply. By the time you pay a technician to look at and try to modify or fix the power supply you could buy a new supply. If you get another supply from the same manufacturer you could wind up with another noisy supply. Other than the suggestion already made regarding wrapping the power chord to the computer around a toroid (a circular piece of black magnetic material, they used to sell them at Radio Shack, I'm sure you can find them on-line pretty cheap). As someone else said a post or two above a GFCI is a safety device to keep you from being electrocuted won't do anything to reduce noise.

Your options are trying the toroid (experiment with the number of wraps, depending on the frequency of the noise it can be anywhere from 1 wrap to ten), finding a power supply that doesn't have this problem, or running on Battery. Modifying a switch mode computer power supply with a ground wire most likely is not going to work and isn't worth the effort to try.
 
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davethangjam said:
cool let me first search in a local shop,if i don't find one then i'll order it from the ebay
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Are you speaking of the power supply? If so do nothing until you tell us what you have now! Does it have a 3 pin "cloverleaf" mains input?

Dave.
 
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