Marantz?s famous in-house tuning tradition tweaks up the PM4400. All the components were re-examined and long and painstaking listening tests have been carried out. Trying one component sometimes force to change another component that have been previously determined. As a result, the PM4400 OSE gives tighter bass and clearer stereo images. The original features such as two-pair of speaker connection are still there since it providesconvenience of bi-wiring connection.