My recorder is a Marantz CDR500, a Pro recorder. As per Marantz today, they advise me not to use anything higher than 32X speed, with recommended discs being TDK, Sony, Fuji, and Taiyo Yuden. My machine records at 2X in the fast speed, if you can believe that. I've tried Mitsui (MAM-A) 1X-16X, but most will not initialize. TDK and Sony music discs are no problem, but I would like to use a better disc.