it's the other way around. it is dangerous to connect multiple PSUs to a single ASIC.  you can connect as many asics you want to a PSU as long as both your PSU and the 6pin connected can handle the power needed. from a theoretical point of view you can have 4 z9 minis connected to 1 APW 1600w psu ( each z9 mini takes about 350w if not overclocked" ). how ever i would not do that until i verify that the 6 pin connectors which are going to be split can actually handle the load.