TRAINEE APCH CTLR HAD LESS THAN STANDARD SEPARATION WITH LGT TURNING WIDE BASE LEG FOR RWY 21 AND AN MLG ON DOWNWIND.

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HAD AN LGT X TURNING BASE LEG; EXTREMELY WIDE AND SLOW TURN; TFC INBND FROM NE DSNDING TO 4000' (OUT OF 4500') BASE TFC DSNDING OUT OF 4000'. ACFT ON BASE RPTED TFC IN SIGHT; BUT NOT TOLD TO MAINTAIN VISUAL SEP. SUPPLEMENTAL INFO FROM ACN 88028: DURING APCH IN VERY CLEAR WX; 25+ MI; WE WERE UNDER RADAR VECTORS TO A VISUAL FINAL TO RWY 21L AT DTW. ENCOUNTERED LESS THAN 1 MI SEP FROM TFC IN OPP DIRECTION. AFTER A 360 DEG TURN; MANY VECTORS AND SPEED UP-SLOW DOWN TYPE APCH WE WERE ON FINAL FOLLOWING VECTORS FOR RWY 21L. WE WERE APPROX 12 MI OUT WHEN CTLR ISSUED TFC AT 11 O'CLOCK ON BASE TO RWY 21L. WE ANSWERED WITH NO CONTACT ON TFC. THE CTLR THEN GAVE US A 90 DEG TURN TO LEFT FOR TFC. ONCE THE TURN WAS STARTED WE SAW THE TFC; AN LGT X TURNING LEFT INTO US. THE REASON WE DIDN'T SEE HIM BEFORE WAS HE WAS HEADED DIRECTLY AT US. BOTH ACFT WERE IN LEFT TURNS BELLY TO BELLY. WE THEN CONFIRMED WE HAD THE TFC IN SIGHT. CTLR STATED 1 1/2 MI APART; BUT WE WERE STILL HEADED AT EACH OTHER. WE PASSED SO CLOSE BEHIND THE LGT X THAT WE HIT HIS WAKE TURB AND WE WERE ALREADY IN A 30 DEG BANK. THE TURB ROLLED THE ACFT TO AT LEAST 45+ DEG BANK VERY RAPIDLY. THE F/O WAS FLYING AND HANDLED THE ACFT WELL. ONCE WE STATED THE TFC IN SIGHT; THE CTLR ISSUED A RIGHT TURN TO FOLLOW TFC TO RWY 21L. I DECIDED NOT TO DO THAT BECAUSE WE WERE SO CLOSE AND WOULD HAVE TO MAKE VERY STEEP TURNS TO DO SO. THE CTLR THEN GAVE US A LEFT TURN FOR A DOWNWIND AND WE RE-ENTERED THE FINAL FOR A VISUAL LNDG. DURING THE VECTORING THE CTLR'S VOICE KEPT CHANGING FROM A MALE TO FEMALE VOICE. SO; I ASSUMED THERE WAS TRNING IN PROGRESS. AFTER WE WERE IN THE GATE AND AT THE HOTEL I CALLED APCH CTLR TO SEE WHAT HAD HAPPENED. I TALKED TO THE SUPVR AND HE INFORMED ME THAT THERE WAS TRNING IN PROGRESS. MY MAIN CONCERN WAS NOT THAT WE HAD A CONFLICT OF TFC; BUT WHY THE TURN INTO EACH OTHER. WE COULD NOT TURN RIGHT BECAUSE OF PARALLEL TFC; SO I THOUGHT A CLB STRAIGHT AHEAD MIGHT HAVE BEEN BETTER. WE APPRECIATE THE ATC EFFORT TO GET THE MOST TFC IN DURING A SHORT TIME; BUT WHEN A GAME PLAN DOESN'T WORK WE NEED A SAFER OUT. THE SUPVR WAS VERY HELPFUL AND PROFESSIONAL IN HANDLING THE PROB.