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Vostro - major audio interference/distortion
Hey all,
Not long ago I got a new laptop – a Dell Vostro 1520, and when I connect it to my sound system (ie into my mixing desk, which then runs to active audio monitors) from the headphone output, I get extremely terrible audio interference/distortion. Very bad. After some experimenting I realised that as soon as I unplugged the power cable and let it run on battery, the sound was immediately crystal clear. This occurs in different houses with different power circuits/sound systems too.
Can anyone tell me how I can resolve this issue? Two options that came to mind (and I found on the internet) might be:
1. Ground Loop issue? If it's this, what are my options? Would lifting the ground pin resolve this? (ie replace the 3 prong plug with a 2 prong plug) Or more to the point, is that is SAFE to do that? . If that's not safe, are there any other ways I can resolve this?
2. Unregulated power supply - If this is the problem, what are my options to resolve this?
3. Anything else?
Any advice would be appreciated, because at the moment I can't listen to any music at all while my laptop is plugged into mains power :(
Cheers,
Manachi
Jim Coates
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February 14th, 2010 05:00
Manachi,
This used to be a widespread problem but Dell eventually got it fixed by redesigning the power block. You should contact Dell about this in case your power adaptor is defective.
I'll paste in the reply I used to give to folks about this.:
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Some of the Dell notebook computers can experience a Ground Loop noise under certain circumstances. This is mainly an issue on the older models.
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.
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I cannot advise you on the safety of using a a 3 prong to 2 prong adapter because I am not qualified. I can say that I do use one on my old Inspiron 1100 computer. By the way it does not matter if the a 3 prong to 2 prong adapter is attached to the computer or the mixer; either way it eliminates the problem for me.