The famous in-house OSE tuning has it roots back in 1990?s. Based on a standard model we are reexaminingall components to find in long and partly painstaking listening sessions the right balance of the best components. Trying one component sometimes force to change another component that have been previously determined. As a result, the PM4001 OSE gives tighter bass, clearer stereo images and a wider sound stage. The original features such as phono input and two-pair of speaker connection with the convenience of bi-wiring connection are still there. The OSE is easy to detect due to the Original SE badge on the solid metal front and of course on the excellent sound quality.