Will a RCA to RCA adapter hurt the sound?

I don’t think that anyone can say with any certainty, so the experiment suggested by R_F_Sayles would seem to be worthwhile. FWIW, though, my guess is that **if** a difference results it is more likely to be caused by the added length than by the adapter. Depending, that is, on the output impedance of the component driving the cable, the lengths that are involved, the susceptibility of the interconnected components to ground loop issues (ground loop issues can be sensitive to the resistance of the return conductor in an interconnect, and therefore to the length of the cable), and other variables.

I assume, btw, that you are referring to line-level analog interconnects.  Not to phono cables or digital interconnects, for which I would recommend against using an adapter.

Regards,
-- Al

Would it be plausible to sell the two pairs of shorter cables and purchase one pair of the length you need?

thks guys= Yes these are line levels from my preamp to my amp- Just extending one meter- Really do not want to take full rack apart move everything then try it and it does not sound right- anyone know which adapter I should get- Does cardas make an rca/rca-??-thanks for all the help---

No way to know for sure other than try and compare.  

Despite the fact that you're asking the question, you already know the answer.  Unless this is a temporary, stop-gap measure I cannot imagine you would settle for this kludge in the quality of system you've put together.  Man up and do the right thing.