PLTS OF MIL FLC DID NOT FOLLOW ATC AMENDED INSTRUCTIONS TO TURN AND LEVEL OFF FROM CLB CAUSING AN NMAC.

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WE DEPORTED NAS MIRAMAR ON THE JULIAN 9 DEP WHICH REQUIRED US TO CLB AT A HIGHER PERFORMANCE THAN OUR NORMAL CRUISE CLB SCHEDULE. PASSING 3000 FT. I CONTACTED SAN DIEGO DEP CTL TO RPT PASSING 3000 FT TO 11000 FT. HE RESPONDED 'CLB AND MAINTAIN 7000 FT. I REPLIED; PASSING 4000 FT FOR 7000 FT. THEN RELAYED IT TO CREW. THE CTLR THEN CAME BACK AND SAID; 'TURN L 310 AND MAINTAIN 5000 FT. I ACKNOWLEDGED THAT AND RELAYED IT TO THE CREW. BUT DUE TO THE INHERENT AMBIENT NOISE OF A P3C FLT STATION; THE ADDED NOISE OF FLYING THROUGH RAIN AND THE HIGHER THAN NORMAL ENG NOISE REQUIRED TO DO THE JULIAN 9 DEP. MY VOICE WAS SOMEWHAT WASHED OUT AND NOT HEARD BY THE CREW. THESE EVENTS COUPLED BY THE FACT THAT THE PF THE AIRPLANE'S COMS SELECTOR HAD MALFUNCTIONED AND BECAME INOP; PREVENTED THE CREW FROM HEARING THE 7000 FT AND 5000 FT ALT AMENDMENTS BY THE CTLR. WHILE PASSING THROUGH APPROX 5700 FT ATC CALLED FOR US TO VERIFY OUR ALT. I TOLD HIM WE WERE 5700 FT AND GOING DOWN TO 5000 FT. THERE APPARENTLY WAS ANOTHER AIRPLANE AT 6000 FT. I DON'T KNOW HOW NEAR A MISS THIS INCIDENT WAS BUT BY THE HIGH TONE INFLECTION OF THE CTLR'S VOICE IT WAS OBVIOUSLY TOO CLOSE. UPON RETURN TO NAS WILLOW GROVE; PA; I CALLED THE SAN DIEGO DEP CTL SUPVR AND WE BASICALLY DISCUSSED WHAT I HAVE WRITTEN IN THIS RPT.