EMI, RF, or the devil's in my laptop

D

dctoms

New member
I've got noise problems with a laptop rig.

The set up:
Dell Inspirion 2200 P4 - 768ram
TASCAM U-122 USB interface
pair KRK RP5 monitors
1: 3' & 1: 6' monster Studiolink cables from U-122 to KRKs
additional Flat screen

-I have a buzz comming through the monitors.
-Its influenced by the laptop screen - buzz changes tone when I move windows on screen.
-If I turn off the laptop screen and just use the desktop monitor the buzz goes away.
-If I unplug the laptop power supply and use both screens the buzz is gone.
-If I unplug the USB cable and leave the monitors on, the buzz is gone.
-I cannot hear the buzz in my headpones - plugged into U-122.
-Switching from cheap cables to the Monsters helped some.

So, the buzz seems to come from the combination of the Laptop Screen and Power supply. But why would unplugging the USB cable stop the hum?

Can anyone suggest how to kill the hum?
 
Not sure (embarassing).

I'm using Monster Cable Studiolink mono RCA to 1/4". Vendor Page: http://www.monstercable.com/productPage.asp?pin=2319

The description says they use "Bandwidth Balaced Connectors." I have aways assumed balanced cables only use XLR connections. Correct? Are my cables balanced or not?

The outs on the U-122 are RCA. Should I use cables that go from Mono RCA to XLR? Does such a thing exist?
 
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no, RCA is unbalanced...so unfortunately you're stuck with unbalanced cables.
There are types of denoisers/hum elminators like this:
http://www.sweetwater.com/store/detail/DTI/
I have no clue how well they work, but some people have gotten good results. My guess would be it's the cables/soundcard that's picking up the noise, and some of these dehummers say they also reduce noise that's in the signal. And it could also be a gound loop problem...who knows!
 
Thanks for the suggestions.

I was able to track the noise down to a old, junky powerstrip...Ockham's razor, I guess.
 
Another suggestion would be to get an adapter that turns your three prong electrical plug on your laptop charger to a two prong. I had lots of noise issues with my firepod for a while, then I tried that and it all went away. Check it out, it's a $3.00 solution.
 
cawhite12 said:
Another suggestion would be to get an adapter that turns your three prong electrical plug on your laptop charger to a two prong. I had lots of noise issues with my firepod for a while, then I tried that and it all went away. Check it out, it's a $3.00 solution.
Click to expand...

even though that may work...it is definintely NOT advisable to do that. Removing the ground from your gear is dangerous to the gear and yourself.


just play it smart. the ground lifts are good for quick fix, but I wouldn't use it for a permanent installation.
 
try using different sockets (i.e. on different sides of the room) to distribute your power... like plugging your laptop into another one.
 
Yep. Switched powerstrips and everything cleared up.

So, I've got a **VINTAGE POWER STRIP** for sale. Comes complete with real club dirt and duct tape residue!!!

Makes me wonder how many sound guys I have irritated using that thing. I've powered a Yamaha CP30 with it for years and always assumed the noise was just the old keyboard.
 
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