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Eliminating ground loop

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cyberbash +

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Eliminating ground loop
When I plug my laptop into my mixer/speakers I've noticed that there's a hum that goes away when I unplug the charger from my laptop. I've researched it and it appears to be due to a ground loop.

I could get a RCA plug ground loop isolator and insert it between my computer and mixer, but I'd rather fix the problem at the root. One of my friends suggested getting a new charger with only 2 plugs (as opposed to my current one which has 3).

http://www.techbuy.com.au/p/83554/Belkin/F5L014au.asp



I was wondering if you guys could tell me
– Will this work to eliminate the ground loop?
– Is it safe to use, as the fact that it has 'Up to 110w of power to increase laptop compatibility' and 'Automatic voltage adjustment' makes me a bit uneasy...

cheers
BradCooper +

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I've tried this and it works.. get a double adaptor.. break off the earth prong and plug in the charger to that - then plug that into the power supply.
Worked for me and i didnt have to damage my charger!
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I fixed my loop by using balanced cables, since i couldn't drop the earth in a PC config (too dangerous and stupid).
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The earth pin is there for safety. Unless your power supply is double insulated, it will have an earth pin. If you disconnect the earth pin by making a bodgy 'double adapter' or breaking the earth pin off, you're making the thing unsafe... an you're an idiot who hopefully is the only one to get a shock from it if it fails. Buy a PSU designed not to have the earth pin if that's the route you want to take.

You can use isolators from Jaycar etc- these will eliminated most of the 'hum'. Technically you're not getting a ground loop but a reference difference... and balanced leads will also fix it as the bring the ground reference to the same level by making a connection between sound card and monitors.

There's 2 to 3 threads on this forum every year about this issue and the solutions are always the same:

1. Don't be a moron and break the earth pin off - buy the right PSU. It'll serve you well both in home studio and at gigs. It wont hurt anyone if it fails - the earth pin is there and connected for a reason.
2. If you don't want to fork out the coin for the PSU try the line isolators - they're < $40.
3. Balanced cables will ultimately solve the issue depending on your sound card and what you plan to plug it into. If you're planning to doing gigs, the isolators aren't a bad idea as you'll find they fit the situation best when gigging as you may not always get the option to plug into a mixer via balanced cables.
cyberbash +

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Quote:

Originally Posted by jester_fu View Post

There's 2 to 3 threads on this forum every year about this issue and the solutions are always the same:

1. Don't be a moron and break the earth pin off - buy the right PSU. It'll serve you well both in home studio and at gigs. It wont hurt anyone if it fails - the earth pin is there and connected for a reason.
2. If you don't want to fork out the coin for the PSU try the line isolators - they're < $40.
3. Balanced cables will ultimately solve the issue depending on your sound card and what you plan to plug it into. If you're planning to doing gigs, the isolators aren't a bad idea as you'll find they fit the situation best when gigging as you may not always get the option to plug into a mixer via balanced cables.


I don't want to go for option 2 because it seems like thats just putting a bandaid over the problem.

If I bought a different PSU, one with only 2 pins like this one:

http://www.techbuy.com.au/p/83554/Belkin/F5L014au.asp


would I be right in saying that it will fix the hum since this PSU doesn't need a third pin by design?
BradCooper +

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PSU would be the better solution.. the "break the earth pin" trick is just a quick dodgy solution that does work until decide to purchase a PSU, but as you say, removing the earth is not cool :\
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Quote:

Originally Posted by cyberbash View Post

would I be right in saying that it will fix the hum since this PSU doesn't need a third pin by design?

Yes, it should.
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