Squeak, if you want the drum machine to play it's own patterns in sync with your arranger,just hook up as shown above,and that will work. However, if you want to use the drum patterns in your arranger with the drum sounds from the drum machine-------well, I don't think so,but I would love to be wrong about this!
.I do understand your desire to get Zoom-quality drums for your psr550 and I wish you the best,but I fear that the answer is replacing the 550 with something else with better drum kits.That was my solution. Again, I hope that I am wrong and some midi-master can show us all the light!
Bill