Long distance between preamp and power amp

 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.

I couldn’t find an output impedance spec on the C712, or anything that would provide an indication of how its balanced outputs are generated. But given that it is a solid state design chances are its output impedance is relatively low. And given that all of the input connections it provides are unbalanced, chances are that one of the two signals in the pair of signals it provides to its balanced output, for each channel, is generated by putting the other signal through a simple op amp stage, ca. 1995. Which in turn suggests that the C712’s unbalanced outputs stand a good chance of providing better sonics than its balanced outputs.

Given those considerations, I would suggest simply using an RCA cable having relatively low capacitance, less than say 20 pf per foot, and providing good shielding. Blue Jeans LC-1 meets those requirements at a low price point.

I suspect that will work out fine. If not, though, a Jensen transformer can be considered, as I mentioned earlier.

Also, FWIW, personally I would much prefer to replace the preamp and/or add a Jensen transformer than replace your amplifier, which is a treasure based on all of the user comments I have seen about it.

Good luck. Regards,
-- Al