Kettle lead in recording chain creates noise

M

musicdavid

Member
I have started to use my laptop instead of my PC to record onto. I'm using exactly the same set-up as before, with the same equipment.

As soon as I use anything which involves a kettle lead, this creates loud distortion. I have every combination I can think of in terms of switching leads on different piece of hardware but nothing makes any difference. As soon as the kettle lead is pulled out, the noise stops. It's particularly annoying as it means I can't use my Mackie mixer which is powered with a kettle lead.

I can only assume it's something to do with the laptop.

Any ideas why this might be happening and how to get around it? Thanks.
 
Pretty common problem with laptops. Has to do with the power supply and a ground loop. Try using your laptop with just battery power and see if it goes away. If it does, you have a ground loop and will need a ground lift on the laptop powersupply.
 
Technically, you shouldn't but personally, I would. Do it on the laptop though. As mentioned, try your laptop on battery power first to make sure that is the problem. Also, you can search for "ground loop" and you will find more info about it.
 
musicdavid said:
I'm no electrician. I assume disconnecting the earth isn't dangerous?
Click to expand...

It's not a good idea, no.

The root of the problem is that the laptop power supply is noisy and has a lousy ground, and as soon as you patch in something else with a three-prong plug, the path to ground through the audio cable shields and out the Mackie's power cord is better than the ground path through the computer's own power supply!

The best solution is probably to ground the laptop properly. Get yourself a three-prong power plug, an 1/8" mini plug, and a few feet of 10 AWG wire at Radio Shack. Solder yourself together a cable that connects the ground of the 110VAC power plug to the ground on the 1/8" stereo mini plug. Put some tape over the other contacts in the back of the power plug so that if the wire comes loose, you won't fry your laptop. Finally, plug the power cord into the wall and the 1/8" mini plug into your laptop's built-in sound card. Ahh. Sweet silence. :)

Now if you're using the built-in audio (why?), you'll have to do a little extra work. Convert that ground lead into a grounding pigtail by wiring up a normal 1/8" stereo mini jack to the 1/8" mini plug using a piece of shielded audio cable. (If you don't want to buy shielded audio cable, just get a shielded 1/8" audio cable, cut off the plug, and wire it to your custom plug.)
 
everyone always says its not a good idea... but seriously your laptop isnt some dodgy high voltage piece of equipment ...i expect on the whole planet there might be a guy who dies from doing this but there are a whole lot more dying from crossing the road..

if its buzzing take off the earth and run that gauntlet!:)

a great deal of the planet doesnt even have an earth but they get by...
 
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