I have a altec lansing subwoofer, I notice that a humung sound comes out when i plug it into my computer but when i plug it on my cellphone the hum went gone. I was puzzled on how can i fix it. I tried to check the power supply and it was ok. Ive read some comments on the internet that maybe i have a bad volume control? can this be the reason why my subwoofer keeps on humung? I tried to unplug the input and the hum will be gone. Please help