Re: 8400GS and crackling noises with DVI connection
DAC stands for Digital to Analog Converter. DVI is digital. VGA is analog. If you plug a DVI cable into a CRT then the DACs inside the monitor are used. If you use the VGA cable instead, then the DACs on the card are used.
There is no real benefit to using DVI for a CRT, in fact, as your case shows, it could be worse than using the VGA cable.