I have heard and I can't personally hear a difference. However, the 640a cd player v.1 to v.2 there is a difference that I could hear. The v.2 is imo the best amp for the money out there. I have the v.1 amp and love it...great bang for the buck.. If you really want to hear the amp sound good, upgrade the power cord from the stock cord.. It will cost about $100 dollars to get a decent cord, but the difference in sound is worth every penny
