I Guess Its Called A Ground Loop Problem

davethangjam said:
what do you mean by 3 pin mains input. yeah all my house have a 3 input plug. but my laptop charger (present) only have 2 input
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OK! Now we know! Forget everything about earth loops. It looks as though you have a "dirty" power unit. Is it an actual Sony PSU? if so I would give them a hard time since...
1) The PSU should be clean.
2) The laptop should be filtered against a reasonable amount of DC borne crap!

Dave.
 
In India they use type D receptacles:
india.gif
Don't know why they wouldn't have two prong to three prong adapters if they have two prong equipment...
 
Ah, but reading the rest of the posts tells me a ground adapter is not going to fix a faulty PSU :D
Go get em, tiger! :thumbs up:
 
Do you have your cellphone on and nearby? I found that interference from my phone was causing big noise through my audio interface. I keep it AWAY!
 
davethangjam said:
yeah the noise disapper with unplug charger ,as i mentioned in the post. @MrClean then how do you fix it?
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I've had this problem before or, at least, a problem with similar symptoms.

In my case I found that putting a meter between mains ground and my laptop chassis read about 3v.
I didn't have the problem when I put a mains powered preamp in front of my interface which got me thinking.

In short, establishing a path from laptop chassis to mains ground solved the problem immediately.

For example, say you connected the laptop headphone output to a mains powered amplifier's line inputs, that may solve the problem as the jack cable shield would, most likely, establish a path.

I do not recommend attempting any DIY ideas or anything like that.

FWIW, my laptop was a dell vostro 1500 with analog video outputs. Dell even acknowledged the need for manual grounding as there were documented issues with video output, for the same reason.
 
Steenamaroo said:
I've had this problem before or, at least, a problem with similar symptoms.
It's almost always filed under ground loop and almost always nothing to do with ground loops. ;)

In my case I found that putting a meter between mains ground and my laptop chassis read about 3v.
I didn't have the problem when I put a mains powered preamp in front of my interface which got me thinking.

In short, establishing a path from laptop chassis to mains ground solved the problem immediately.

For example, say you connected the laptop headphone output to a mains powered amplifier's line inputs, that may solve the problem as the jack cable shield would, most likely, establish a path.

I do not recommend attempting any DIY ideas or anything like that.
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This is DEFINITELY worth a try. Electrically solid advice as you are grounding the chassis to something that is grounded. (you don't have to monitor the other amp, just use it to ground your chassis). Specifically, plug in as described, turn on the grounded power amp (home stereo, whatever) and turn the volume off (you may not even have to turn the amp on, depending on it's circuitry). The headphone jack is grounded to the chassis, the amp is grounded to earth. MUCH easier than removing the case and running from the monitor ground to a grounding adapter as some dufus suggested :facepalm:

If that fails, you're definitely going to have to work toward getting your power supply replaced.
 
bmong88 said:
Do you have your cellphone on and nearby? I found that interference from my phone was causing big noise through my audio interface. I keep it AWAY!
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I don't think that would make a change when you unplug the laptop...but it's an easy check. :D
 
Something to try if at all possible is taking the whole rig to another location and checking the noise performance.

A modern office perhaps?

Dave.
 
What I should have also mentioned was that the cell phone interference was seemingly random. Actually the noise would stop sometimes when I turned off/on my monitor amp or changed a signal path in outboard gear trying to troubleshoot it. After a few months of the annoyance I realized it was the cellphone actually causing the interference. Again, sometimes unplugging something seemed to stop the noise but in actuality it was the cell radio transmitting something. Doh. I figured it out when I had my cell phone next to another computer in a different location and the 'noise' was the same frequency coming out of that computer's own connected speakers which was nowhere near my studio but on the same wifi network. Anyway - something to try that's painless!
 
I've found a good solution,i'm gonna sell my laptop tonight and work with my desktop again. and by that time i'll save up for a mac book so that i'll have no issue next time :)
 
I have been involved in the radio business in the past where I had to fix some switching power supplies. In every one and they use them for pro broadcast equipment too there is no connection of any kind from the AC terminal to the DC output(s) of the equipment. They are totally isolated. If the power supply is old and has many hours on it it can have failing caps in it. You might have to replace it. Many people in the Radio business come first to the Chief Engineers office to get solutions to their Electronics problems.
In this I have replaced a lot of supplies in looking at what was available at Marlin P Jones and Associates or MPJA.com and getting a supply that is as good or better than what they have and maybe having to change a connector on the DC side.
I think your problem stems from a difference of ground from the USB interface and the laptop. The first step to try which is the cheapest is to attach a alligator clip to some ground terminal on the laptop to a ground on the interface. See if noise goes away. It is not common that an interface will be getting hum from a power supply as they operate in the 50-70KHz region and those are filtered out with toroid coils.
It is not likely a ground loop in the typical sense.
 
skywaveTDR said:
I have been involved in the radio business in the past where I had to fix some switching power supplies. In every one and they use them for pro broadcast equipment too there is no connection of any kind from the AC terminal to the DC output(s) of the equipment. They are totally isolated.
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But presumably something in the chain isn't isolated.
The power amplifiers, desktop computers...whatever.

skywaveTDR said:
I think your problem stems from a difference of ground from the USB interface and the laptop. The first step to try which is the cheapest is to attach a alligator clip to some ground terminal on the laptop to a ground on the interface.
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I'd certainly recommend trying this, but in my case there was continuity.
 
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