Kevin Hartz, a co-founder of Eventbrite and longtime startup investor, has watched as venture capital firms unveil multibillion-dollar funds to back cash-hungry AI companies at every stage of their lifecycles. He’s taking a different approach.A-Star, the early-stage venture firm Hartz launched with former Coatue investor Bennett Siegel, is set to announce on Tuesday that it’s raised $450 million for its third fund — its largest to date, but a far cry from the $15 billion fund that Andreessen Hor