2 unit active analog transformers. Not re-clocking devices, but reduces R.F.I./ E.M.I. & cleans up data stream between transport & DAC.Comes w/ digital cable, but will make any coax. cable sound better.Google Positive Feedback. com, go to archives & type Audient Technologies. Go to Dynamic Design site, & read review. Also Vol. 5, #3, 5, & 6.Was also endorsed by Ron Hedrich of Marigo Audio Labs. If you still listen to 16 bit cds, for this price, it's definitely worth checking out!