Good points by Swampwalker and Dan_Ed. Would a different room be better? Yes, since acoustic feedback is certainly an issue.
However it's far from the only issue and your mechanic was half wrong, or only half right. You should move your TT to an isolated room like Ianlane's AND use your isolation goodies.
A major source of vibrational energies affecting a vinyl rig comes from the stylus-vinyl interface. The earth's noise and other vibrations entering throught the floor and TT supports are also a factor, especially in very sensitive systems like yours. These will be a factor no matter what room the TT is in, even if it's in Dan_Ed's neighbors' house!
However it's far from the only issue and your mechanic was half wrong, or only half right. You should move your TT to an isolated room like Ianlane's AND use your isolation goodies.
A major source of vibrational energies affecting a vinyl rig comes from the stylus-vinyl interface. The earth's noise and other vibrations entering throught the floor and TT supports are also a factor, especially in very sensitive systems like yours. These will be a factor no matter what room the TT is in, even if it's in Dan_Ed's neighbors' house!