Hi Guys
I agree with Samoyed .i have had the nc500 for 3 years now and must say the rev d boards do make a difference,i have tried both flavours of op amps having firstly dismissed the sparkos because of a fuzzy top end from new,having spent 3 months with the sonic imagery i could not live with the slightly lightweight presentation so switched back to the sparkos after 300 or more hours use the have undergone a transformation opening up to such a degree i cannot believe it to be the same op amp ,gone is that fuzzy top end ,the midrange has opened out too and the bass has more definition to it,the sparkos sounding fuller ,both op amps displaying the same level of detail, though, the sonic imagery will sound like it has more because of its lighter presentation it is all there with the sparkos.