Did updating your audio driver help the situation? What model of Inspiron are you using? Try using a set of headphones instead of connecting the audio output to your amplifier.
To keep you all updated. I have just had my laptp returned this afternoon after being in service for 2 weeks , ttech told me it would take no longer than 3-5 business days, 2 weeks later they have returned it . They told me they had replaced the motherboard yet there was a letter with my laptop saying they had done a suite of tests and diagnostics and could not recreate the fault and could not find any malfunction with my laptop. I have just this minute set it up again and lo and behold the static sound is STILL THERE, i cant belive it.
The staic sound is still only present when i am using the ac adaptor, when running on battery it is fine, i phoned customer care and toild them this , i also included the ac adaptor when the laptop was returned. I am waiting to hear back from them. Maybe they will send me out a new ac adaptop, why they didnt givem me a diffedrnet one when it was returned i don know.
I have just spent the last 2 weeks having to go to an internet cafe to check my mail and i recieved my phone bill yesterday, £40 woth of call charges to tech support about this problem. I have been driven to despair and i think it has now reached the stage that i will give them one more chance, if the fault isnt fixed i shall bed contacting trading standards and demand a refund on the grounds that they have supplied my with unmerchantable goods.
If anyone has any answers please let me know, i explained all of this to tech support about the ac adaptor and battery but they have obviously not taken any note of this . I just want to get the problem solved or if it cant be then have my hard earned money back with compensation and then move on with my life.
I have the exact same problem....it hums when connected to external speakers, when the AC is plugged in. With headphones it sounds fine. Checking all the various mute switches in the sound properties makes no difference. I sent it in to Dell, it came back with a note "updated bios", but it still makes the noise.
This is totally unacceptable....I'll be returning it if I can't find a solution soon.