New Computer, New Noise

Jeremy Steele · From: Princeton, NJ USA

I'm hoping one of you gurus can help me...I record using Audacity, and I just replaced my old desktop (which ran Windows XP) with a new Dell Studio 17 (which runs Vista)laptop....I find when I try to record with the AC adapter plugged in I get all sorts of staticy type interference...the same holds true when I try to play songs from my itunes library through an external mixer/amp...the noise goes away when I unplug the adapter and just run the unit on the battery...any ideas how I can fix this?

Jack Stoner · From: Kansas City, MO

I do a lot of Dell support and with a new PC, best to call Dell as it sounds like potentially a defective part - either the charger or the internal AC power conversion.

Also, if this is within the Dell 21 day return windows (for PC's bought directly from Dell) and you can't get it corrected with Dell support you can call Dell customer service and request a return and in many cases they will offer to replace it with another new system rather than have to issue a refund. The 21 day period is from the date on the invoice (usually the date it was shipped).

There is also a Dell Users Forum and you can post the problem in the Laptop General Hardware section and see if someone has an answer for you. http://en.community.dell.com/forums/3518.aspx

Jeremy Steele · From: Princeton, NJ USA

Thanks for the suggestion Jack...here's what I learned on the Dell Forum, FYI.

Some of the Dell notebook computers can experience a Ground Loop noise under certain circumstances. This was mainly an issue on the older models, so you might want to contact tech support to see if you have a faulty adapter. Or it could just be that Dell has redesigned the adapters and they are bad again. Yours is the second post I've seen about this problem recently after a couple of years of not hearing about it..

Symptoms Include:
1. A scratchy, staticy noise when moving the cursor, and
2. The noises occur only when the computer is plugged into its power adapter and not running on battery power, and
3. The noises occur only when the computer's output jack is connected to another device (like a mixer, power amp, etc) that is also plugged into a/c current with a grounded plug (3 prongs).

If you have similar noises but under different circumstances then it is not this Ground Loop noise.

To Diagnose:

1. Disconnect the power cord from the computer and run on battery power, or

2. Eliminate the ground either on the computer or on the other device it is connected to, by using a 3 prong to 2 prong adapter available at hardware stores. Use this adapter just as a temporary diagnostic tool because eliminating the ground can be potentially dangerous and could cause your warranty to become invalid.

In either case if the noise stops then it is the Ground Loop. It is caused by the design of the notebook's power adapter and there is no repair or replacement that can fix it, but there are some workaround solutions.

Solutions:

1. Isolate the grounds from each other by using a ground isolator. Several forum members have given us positive reports on Radio Shack's $16 Ground Loop Isolator (270-054). There are other such devices available for more money which would probably be better for someone doing pro audio work.

2. Or use non-conducting material to connect the 2 devices; specifically by using optical spdif (Toslink) to transfer the audio signal rather than copper cables. This is not as practical as the 1st solution because the notebook computers don't have an optical spdif port, so this would require getting an external soundcard that has optical spdif output, and a receiving device that has an optical spdif input port.

An external sound card is not in itself a solution, because you will still get the Ground Loop if you use its regular metal jacks to make connections, if the other circumstances described under 'Symptoms' are also present.

Jack Stoner · From: Kansas City, MO

Thanks for the update. I'm not up on most laptop problems as I do most of my support is in the Desktop Audio and General Hardware sections.

(I'm "fireberd" on the Dell forum).

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