Don´t know the mcd-500 but my two cents FWIW.
I have been playing the CD-2 through a MA-6600 .
It is far better on direct connection using the digital volume of the c-2 than using the 6600 preamp section .
Using the Ayon cd-1 is just the opossite , that is using the 6600 preamp .
Both Ayons sounds best with the digital volume between -10 to -5 , never use the full output. IMHO.