I would add a couple of things to what Al said. The ratio of the output impedance of the phono preamp to the input impedance of the linestage should generally be at least 1:10 and preferably 1:20 though there are certainly exceptions and otherwise fortuitous combinations that don't meet these criteria.
All is not lost if you have problems. A buffer can be installed at the output of the phono preamp to drive the long cable run. Yes, it's another box and another set of interconnects, but sometimes this is the only panacea in these situations.
Another concern with long cable runs can be radio frequency interferance, and this can be a bit harder to cure. Certainly, you should use a sheilded interconnect for runs of that length at the least.
All is not lost if you have problems. A buffer can be installed at the output of the phono preamp to drive the long cable run. Yes, it's another box and another set of interconnects, but sometimes this is the only panacea in these situations.
Another concern with long cable runs can be radio frequency interferance, and this can be a bit harder to cure. Certainly, you should use a sheilded interconnect for runs of that length at the least.