This is the Lexicon MPX550. It has been tested and is fully functional, with no crackling. The sound is similar to the higher-end PCM series models. There are a few minor scratches, but otherwise, it's in excellent condition with no noticeable damage. This is a product from when Electri was the distributor. The MPX550's rotary encoders are known to experience contact issues over time, causing the values to jump (data skipping). Therefore, all five rotary encoders on the front panel have been overhauled. They are all working smoothly now. #Yamaha