imaband,

1. 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. This fix should only be used for diagnosing the problem ... if this eliminates the noise use one of the other solutions for long term.

2. Or isolate the grounds from each other by using a ground isolator or a direct box with ground lifter. Several members have given us positive reports on Radio Shack's $16 Ground Loop Isolator (270-054).

3. Or use non-conducting material to connect the 2 devices; specifically by using optical spdif to transfer the audio signal rather than copper cables. (You would need to have an external soundcard with optical spdif... like some Soundblaster cards.)

Jim

Thanx for this reply Jim. I have an Inspiron 8500 and have been using it for serious home studio recording and I get terrible ground loop feedback complete with hard drive feedback through my studio monitors. Unplugging the unit eliminates the sound. I tried to use RF chokes from radio shack but to no effect. I will investigate this 'ground loop isolator' dealie from radio shack that you speak of.

I was also wondering if perhaps a pro-audio rack mount power conditioner would filter out the noise. It is totally disrupting my ability to use this computer for its intended purpose. . .

I just bit the bullet and purchased a tripp lite isolation transformer for about 80 bucks.  I am waiting for it to get here in the mail but if it works it will definitely be worth it.  I have lost too much time fretting over this problem.

I'll let you know how this turns out!

Well I got the isolation transformer in the mail, plugged it in, plugged my computer into it and the sound was still there!!! AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAARRRRRRRHHHHHGGGGGG!!!!

I feel like Charlie Brown right now. After spending HUNDREDS of dollars on 2 breakout audio interfaces, radio shack rf chokes, an isolation transformer that supposedely "eliminates RF and EMI interference" and never feeling the least bit good about it I am ready to take this $2500 dollar laptop and throw it out the window! I have spent TWO YEARS trying to eliminate this problem and I have totally, utterly, failed.

Message Edited by logikbomb on 06-14-2005 04:57 PM

I didn't say it wouldn't work long term, just that it should be used as a diagnostic test and not long term, because the ground is a safety feature.

Usually this works equally well whether the adapter is used on the computer or the other piece of equipment.

Jim

jimco

What sort of an adaptor do you mean? Maybe because I'm in the UK I'm not aware of there being any way of getting mains into my Dell or (say) Yamaha keyboard without using a 3-prong mains plug

Thanks

Giles

logikbomb

Don't give up yet. I too have been having this problem for ages. It even happens in this way:

1. I connect my PC to my Yamaha stage piano via MIDI
2. I connect my Yamaha to an external amp
3. There is noise coming out of the amp

What I reckon is that the power supply wiring in the Dell is dodgy somehow and it essentially puts a signal on the ground/earth of ALL peripherals, i.e. USB ground, audio ground and MIDI ground for example. To such an extent that it mucks up the grounding on the Yamaha. I'm not sure that it is even a usual "earth loop" as it doesn't sound like "mains hum", but I may be wrong.

I used a simple DI box with earth lift (Behringer DI20 I think http://www.behringer.com/DI20/index.cfm?lang=ENG) as suggested elsewhere here between the audio outputs and the amp and that cleaned up all the noise. I plan to do some more tests when I have time to understand better what is going on.

The radio shack device looks like it should do the same, though the cables look a bit cheapo so you may get better signal using a Pro quality DI box with pro cables - and the signal coming out of the DI is balanced.

From talking to someone in a Pro Audio shop the other day it looks like this may be a not uncommon problem these days with laptops.

Good luck!!

Giles,

the adaptor is a simple 3 prong to 2 prong plug available here at hardware stores. It eliminates the ground wire and leaves the hot and neutral.

Jim