Monitor is causing hum in microphone recordings.

[LokiNya]

I've recently bought a dynamic microphone and mixer and connected it to the line-in of my sound card. When I'm playing back what I've recorded, I can hear an annoying hum.
So I tried to track the problem and it seems the hum is gone when I turn off my monitor.

I don't have grounded wall sockets in this room, so I connected everything with an extension cable to the grounded socket in the bathroom. Sadly, the hum wasn't gone, and I gained another hum in my speakers when it's grounded. :eek:

Has anyone here maybe some ideas on how to fix this?
Would a "Ground Loop Isolator" between mixer and sound card help? Or some of those ferrite clamps on cables? :confused:

Here's some more info.
Microphone (Shure pg48) is connected to mixer (Behringer Xenyx 802) and the mixer goes to the line-in of my sound card, and from my sound card output an amp with a pair of speakers.
Monitor is a SGI GDM-FW9011 24" CRT

[BakedA|aska]

A ground loop isolator wouldn't be a bad idea. What would really help, I think, is a power conditioner. Ferrite beads wouldn't hurt, either.

LCD monitors all have one or more small fluorescent tubes, which requires a high voltage ballast circuit to be driven. To me, it sounds like that ballast may be "leaking", causing the EM interference you're hearing.

It's either a leaky ballast in your monitor, or an issue with EM noise in your home's electrical wiring. Both problems are usually fixed by isolating ground, and conditioning power.

[LokiNya]

Thanks BakedA|aska.

I don't have an LCD monitor, but a CRT (there's a topic about this monitor here (http://hardforum.com/showthread.php?t=952788))

While recording I moved my microphone a good 2 meters away from my monitor, and the hum was gone, so doesn't look like the interfering signal is traveling through the cables or a ground loop, but some RF interference or magnetic field that my monitor is creating or something.

Hopefully, it's the cable that picks up most of it, then I guess a quick fix are some ferrite beads on the XLR cable, or make a heavy shielded cable myself. If most of it is picked up by the microphone, which is more likely I guess, I'm not sure what to do. :(

[BakedA|aska]

Thanks BakedA|aska.

I don't have an LCD monitor, but a CRT (there's a topic about this monitor here (http://hardforum.com/showthread.php?t=952788))

While recording I moved my microphone a good 2 meters away from my monitor, and the hum was gone, so doesn't look like the interfering signal is traveling through the cables or a ground loop, but some RF interference or magnetic field that my monitor is creating or something.

Hopefully, it's the cable that picks up most of it, then I guess a quick fix are some ferrite beads on the XLR cable, or make a heavy shielded cable myself. If most of it is picked up by the microphone, which is more likely I guess, I'm not sure what to do. :(

The fact that your monitor is a CRT probably has something to do with it. If I had to venture a guess, I'd say the flyback transformer or the circuits ancillary to its operation are leaking. What sort of pitch does this hum come in at? I'm assuming it's not 60hz.

[LokiNya]

Hmm, If that would be the case, I guess it will involve replacing parts? Any way to confirm if that is the problem?

Here is a short recording I made on a high volume. It begins with the monitor on, then you can hear a click. That's me turning off the monitor and later turning it on again.
You can also hear some static, but that's only noticeable at these volumes.

http://www.megaupload.com/?d=162LP7G3

(sorry about the megaupload, can't access my ISP's webspace atm.)