Long distance between preamp and power amp

There’s no reason to consider selling such a fine amp. If it proves to be necessary you could connect a suitably chosen Jensen transformer (ca. $275) between the preamp and the amp (close to the amp), to convert balanced to unbalanced. That would provide essentially all of the benefits of a balanced connection.

But it may very well not be necessary. What is the make and model of the preamp?

The approach that is best may very possibly depend on several different characteristics of the preamp. Including its output impedance; how its balanced outputs are generated (and therefore whether the sonics of its balanced outputs are likely to be better than, worse than, or similar to the sonics of its unbalanced outputs); and its internal grounding configuration (that may affect susceptibility to ground loop issues, which can be brought out by long lengths of unbalanced cables).

Regards,
-- Al

 I used a 7 meter cable for years between pre and power amp. It sounded fine  , but I always felt it HAD to be a weak link. When I was able to reconfigure my system I went to a much shorter and more expensive cable. Damned if I could hear the difference.

As many of you say, maybe the distance is not an issue after all - as long as I use a good cable. 
My preamplifier is an old (and mint) McIntosh C712. 

yes, my better suggestion is to sell the amp and get one with _true_ balanced inputs

monoblocks should be even better

you can certainly get away with a long RCA run - I did it as a student with Advent speakers and Dynaco gear, but if you want to maximize the SQ do the above

Agree with randy11,

Always been a long IC , short SC fan. Recently found a pair of 30' balanced ICs of my preferred brand and at a reasonable price. (Rare find and Rare price). SQ took the maximum leap.

RCA could be worked with, but was always a bit compromised.

 I begrudgingly worked with the RCAs ( equipment that I had and cost of ICs I wanted ) made it big dollar proposition to make a wholesale change. Thankful for A'gon. Pleased with system more than ever.