On my Virus b, I use PWM with a fairly fast LFO rate modulating the PW. The trick is to detune the oscillators and turn on Unison with a wide spread to make it sound really full. Then just adjust the envelopes to your liking. Sorry if this is too vague. There's a great Virus pad tutorial at
www.trance.nu.
Peace \/
Dan
www.soundclick.com/chisel316