Your problem is not at the machine, it is the desk itself. The desk was made to be light weight, so small vibrations are amplified throughout the desk all the way to the feet. Can't tell you how many of these desks I had to replace when I worked office management for Uncle Sam. Just the weight of files etc on them was destructive. Then people would decide to "sit" (semi-lean) on the edge and they would totally bend. Try adding weight down low on the desk legs, or perhaps extra legs made from 4x4 lumber.
I did exactly what you did but with a plywood desk that has solid ends clear to the floor, and I have no vibration. Good luck.