Finally got some time!
Went to sewing store, didn't get motor. The one in store has " electronic servo motor " tag, owner said it is family brand. When I try it, is different than mines. speed at 0, motor doesn't run ( mines runs ), at 350, little bit noisy, at 660, little bit more noisy, so higher speed gets nosier ( not that loud as my clutch motor, but still get little noise ).
Back home, tried servo motor on my pfaff, put at speed 0, sew so slow, at 350, no noise at all, at 660, no noise at all, at 3450 no noise at all, quiet!
Yours runs at speed 0? DrmCa.