30 ft rca run too long for a phono to preamp?

I would first do everything possible to make things work for the turntable at its current location. If this is not possible, I would suggest moving the preamp along with the turntable to the new location. The phono stage's voltage output (at line level) is not so much the issue but rather, the preamp (line stage) output stage is likely to be able to better "handle" driving long ICs to the amp than a phono stage's output to drive the same ICs to the line stage input. But still, there is no guarantee this will be a success.
John

Just to chime back in here, I ran a 30 feet RCA Purist Dominus IC from line stage to amps for a couple years and had no hum/rfi issues at all. What people echo from what they have read vs. what they have experienced are very different things. Pushing the requirements for balanced ICs is an unnecessary issue. And converting to/from balanced with bogus adapters will accomplish nothing as well. All of this aside, I still would put every effort into making the current turntable location be a success.