Noise with laptop on AC

20 Jan 2005, 12:42

I'm using a laptop (an HP zd7000) in conjunction with my Fantom S88. I have a 16-track mixer, and I have the ZD outputs and Fantom outputs going to seperate channels, then from the master to powered studio monitors. The problem I'm having is when the ZD is on AC it is causing the Fantom to emit a kind of crackling, fuzzy noise. If I unplug the AC it goes away, and the reason I think it's coming from the Fantom is that if I bring the sliders down on its inputs on the mixer the noise also goes away. So it would seem that some component in either the transformer or something else in the power train is causing the noise. It's not 60hz ground hum - so that rules out a ground lifter - it doesn 't have a pitch, rather just crackling.

Anyone else run into this? Any solutions?

TIA

Ken

Ken

Re: Noise with laptop on AC

20 Jan 2005, 19:43

Sounds like some sort of random RFI, perhaps generated by the laptop transformer. If you have access to another power supply you can try that.

Re: Noise with laptop on AC

20 Jan 2005, 21:08

This is an especially common problem with laptops, and it affects all kinds of people in different ways.

I'll guess that your AC Adapter is a 3-prong type correct?

If so, consider one of the following fixes:

1) Get an adapter that converts a 3-prong AC plug to a 2-prong plug.

2) Buy a "Universal Laptop Adapter" that has a 2-prong AC plug.

3) There are other solutions, but they are much more complex and expensive.

Re: Noise with laptop on AC

21 Jan 2005, 05:06

about the 3 prong AC connection, get someone to check to verify that it is connected right
in the states you should be able to connect a tester to the ground hole, with the short slot of the receptical and get ~ 120, and when connecting the short slot to the long slot, ~ 120...but you should have 0 volts when connecting long slot to hole
older houses may have been fitted with 3 prong outlets, but in fact have no grounding electrode connected, (they did it so you can plug in stuff, (NOT GROUNDED...smart)

i also had this hum, it seemed to be related to grounding
i also got a smlall soundcard i velcro to the lid of my laptop (M-audio transit, or Mobile pre), hat helps alot,
the transit is cheap and small, consider it

its not the size of your kit, its what you do with it!

Re: Noise with laptop on AC

23 Jan 2005, 12:36

Thanks very much, folks. You've given me a bunch of things to try In the meantime, I've gotten rid of *most* of the noise by running an extension cord from an outlet on the other side of the room. I was also able to reduce the noise by simply plugging into another surge strip. I have a snake pit of cords under my Fantom, since I have my desktop, various peripherals, a mixer, powered monitors, etc, all together in the same area creating the typical studio mess of wires which I realize is a classic scenario for noise. It was not ground hum though, a sound I know well. I'll still try the 2-prong ground lifter, as yes, the laptop AC adapter is a 3-prong.

Ken

Ken