long RCA cables . . .where?

Long cable from MC amp to preamp.

could the signal be deteriorated in some form with 20ft of cable?

quite possibly.

Long cables from the MC preamp to other preamp. There is no other choice.

Thanks for your input.
Any more ideas about any significance lost in signal quality with this long run?. Thx.

Is the mc amp a phono stage, which provides riaa equalization and a line level output? Or is it just a step-up, which outputs a moving-magnet phono type of level?

I would not want to run a phono-level signal through 20 feet of cable either before or after the mc amp. If the mc amp outputs a line-level signal, you may get away with it, provided that:

-- the output impedance of the mc amp is low.
-- the cable capacitance is low.
-- the shielding in the cable is high quality.

The only conclusive way to tell is to try it, of course.

Regards,
-- Al