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"Ground lifting" to eliminate noise from Computer

I heard a hum/static through my monitors and headphones when using my Firepod... After a while, I eventually traced the problem to the power adaptor for my Laptop. When plugged in, there is a hum, and when not plugged in there isn't. This must be due to the ground... therefore, I'm trying to figure out the best way to solve this problem. I know that Ground lifting is generally dangerous and not recommended. IF anyone has a tip on how to keep my computer plugged in and to eliminate this hum from the adaptor (ground) that would be helpful. Thanks.

Comments

Member Thu, 04/12/2007 - 05:37
Some ideas:

Plug the power adaptor to different ac outlet than the rest of your gear.

Turn the power adaptor 180 degrees and replug it. Sometimes it works.

Use a good UPS and plug your laptop's power adaptor to the battery bakup outlets. You should do this anyway.

Try Ebtech's hum eliminator.

Try a balanced power supply.

Member Thu, 04/12/2007 - 06:08
JCarlo wrote: Some ideas:

Plug the power adaptor to different ac outlet than the rest of your gear.

Turn the power adaptor 180 degrees and replug it. Sometimes it works.

Use a good UPS and plug your laptop's power adaptor to the battery bakup outlets. You should do this anyway.

Try Ebtech's hum eliminator.

Try a balanced power supply.

I tried plugging it into my power conditioner and my regular surge protector, and I still go the same hum.

I turned the power adaptor - doesn't do anything.

What is a UPS? I can only think of "universal power supply". How do you plug the adaptor to the battery backup outlets?

I'll look into the Ebtech.

Please elaborate on a balanced power supply.

I'm still new to DAW recording, so forgive me for my ignorance on some of your suggestions.

Thanks!

Link555 Thu, 04/12/2007 - 06:49
It might be the switching power supply in your computer, which can cause a lot of trouble in the audio band.

Here is some useful background info:
http://www.epanorama.net/documents/groundloop/home_solving.html

I believe the Firepod is not connected to earth; does it have a wall wart transformer with only 2 prongs?

Does you laptop power supply have an earth connection (2 prongs or 3?)?

Do the monitors have an earth connection?


Here is a line isolation transformer (best solution):
http://www.hammondmfg.com/171.htm
This will isolate your PC from the other circuits.

or this -which may not be as good but much cheaper: HUMplug-e
http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html

Best of luck.

Member Thu, 04/12/2007 - 07:38
Link555 wrote: It might be the switching power supply in your computer, which can cause a lot of trouble in the audio band.

Here is some useful background info:
http://www.epanorama.net/documents/groundloop/home_solving.html

I believe the Firepod is not connected to earth; does it have a wall wart transformer with only 2 prongs?

Does you laptop power supply have an earth connection (2 prongs or 3?)?

Do the monitors have an earth connection?


Here is a line isolation transformer (best solution):
http://www.hammondmfg.com/171.htm
This will isolate your PC from the other circuits.

or this -which may not be as good but much cheaper: HUMplug-e
http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html

The HUMplug-e is what I would need. The first one (isolation transformer) looks good, but a little bulky... it would be a pain to carry around with my portable DAW. Also, I can't seem to find a price on that one (unless I called).

To answer your questions:
The firepod is not a wall-wart. It is a 2-prong "central station" power supply seen here: http://images.google.com/imgres?imgurl=http://www.presonus.com/store/images/PSfirepod.gif&imgrefurl=http://www.presonus.com/store/index.php%3FcPath%3D28&h=68&w=73&sz=3&hl=en&start=6&um=1&tbnid=rtZJnFHZMPaFZM:&tbnh=65&tbnw=70&prev=/images%3Fq%3Dfirepod%2Bpower%2Bsupply%26svnum%3D10%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DG

My laptop power supply is a ground connection (3 prong).

My studio monitors are both 3-prong (however they are not the problem - only the laptop creates the ground loop when plugged in).

Thanks.

Member Thu, 04/12/2007 - 10:30
Link555 wrote: Thanks Ardroth,
Ok so the firepod has a floating chassis. Which mean there is no earth connection, IE no third center prong.

All and all I think the HUMplug-e, should work, but if doesn't the Hammond iso-transformer will.

Yeah, I agree... I ordered the Ebtech HUM-X from Amazon.com for $60... hopefully it will solve my problem. Thanks for the help man.
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