AN AIRBUS 300-600 IN CRUISE AT FL330 DECLARED AN EMER DUE TO LOSS OF CABIN PRESSURE. UNABLE TO CTL IN AUTO AND MANUAL. CAUSED BY FAILED RELAYS.

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HAD FLOWN THIS ACFT ON 2 LEGS THE PREVIOUS MORNING WITH THE #2 PRESSURE REGULATOR INOP. PREVIOUS WRITE-UPS INCLUDED THAT THE CABIN 'HAD DUMPED' AT 3000 FT ON THE FLT PREVIOUS TO MINE. MAINT HAD DEFERRED THE #2 REGULATOR IN RESPONSE; BUT COULD FIND NO OTHER PROBS ON THE SECOND FLT. FLEW ON THIS ACFT ZZZ-ZZZ1. THE FLT RELEASE PAPERWORK SHOWED THAT THE #2 PRESSURE REGULATOR WAS STILL DEFERRED. WHEN I REVIEWED THE AML; I NOTICED THAT ZZZ MAINT HAD DONE SOME TROUBLESHOOTING. ANYWAY; THIS DIDN'T HAVE A BEARING ON THE INCIDENT I'M RPTING. ENRTE TO ZZZ1 AT FL330 WITH THE #2 REGULATOR OFF AS REQUIRED BY THE MEL; WE BEGAN TO LOSE CABIN PRESSURE AND THE #1 PRESSURE REGULATOR SHOWED THAT IT WAS FAULTED. THE FO WAS PF AND AS PLT MONITORING; I WORKED THE PROB INITIALLY. THE ECAM CALLED FOR MANUAL PRESSURIZATION PROCS. I TRIED TO CTL THIS LOSS OF PRESSURE WITH THE MANUAL CTLR. I COULD NOT CTL IT. THE CABIN RATE OF CLB WAS PEGGED OUT. I TOOK CTL OF THE ACFT AND COMMANDED THE FO ADVISE CTR OF OUR SIT AND TO DECLARE AN EMER. I HAD 3 JUMP SEAT PAX IN THE BACK AND MADE THE DECISION TO DO A FULL-BLOWN EMER DSCNT. WE ACCOMPLISHED ALL APPROPRIATE CHKLISTS AND LEVELED OFF AT 10000 FT. WE HAD PLENTY OF FUEL AND WE CONTINUED AND LANDED AT ZZZ1. MAINT DISCOVERED THAT SEVERAL RELAYS DOWNSTREAM OF THE REGS HAD FAILED CAUSING LOSS OF CTL OF THE OUT-FLOW VALVES. IT IS MY BELIEF; THAT THE ACFT PRESSURE VALVES FAILED AND THAT EVENTUALLY WE OVER-PRESSURED. THUS; THE EMER RELIEF VALVES OPENED AND THAT'S WHY WE COULDN'T CTL IT.