I'm recording from my laptop on my PC (from my laptop's line-out to my PC's line-in), but there is electrical noise in the background (noticeable when the audio is low).

It disappears completely when I run my laptop off the battery.

What's the best solution for this? Better soundcard, cables....?

Laptop bult-in soundcard isn't always very good...
I've repaired 4 laptopts during the last month and ALL of them had background noise in line-out. If you need high quality audio on your laptop go for an external soundcard (ie Aureon 7.1 firewire if you have firewire connection on it)

Best Regards, Giorgio

I'm not a laptop user but I've read that complaint a number of times. My strong impression is that it is almost always poorly filtered power supply noise - the basic stuff the laptop lives on. I've also seen, without paying any great attention, lists of which laptops work for recording and which don't (don't in the sense of being able to make decent recordings). since the power supplies are not readily replaced with another having better characteristics, you are probably left with battery use. Different soundcards , cables, or any after-the-fact fix is unlikely to be of any benefit.

If you have somehow recorded decent audio on your laptop and just wish to transfer it to another computer, soundcard to soundcard is not the way to go. If you have ethernet on your laptop, transferring the file that way should avoid the noise and it to be highly preferred anyway. Perhaps you have just not been specific enough about what you are doing, but it reads like a D to A to A to D transfer, which is never the best idea, no matter what soundcards. It is preferable to always keep the information in the digital domain if possible.

It ethernet isn't a possibility, then digital to digital via the soundcards would definitely be better. If the laptop has no digital out then an external soundcard with digital out might help. If you can't use firewire (best), look for USB with its own power supply. Too many USB cards (but not all) will pick up the computer's power supply noise on the audio stream if they are using that power for their own operation.

I agree , and in support of this: my own setup uses the laptop to run foobar 2K, with source files on an external drive, and USB connections from external drive to laptop to home theater receiver (which has a USB input). The receiver is essentially the soundcard in this sort of setup. When using the laptop AC adaptor, there is low-level audible noise at the loudspeakers; when running the laptop on battery power, it's dead quiet.