Hello, I have a Yamaha P90 digital piano. I have not used it for some years, yesterday I turned it on and it seemed to me that the sound is still not as great as I remember. It seems there are some artifacts (or noise distortion) around the Mib 4 . It could be something around the output preamp (from the schema, there is a double opamp there). The same issue appears on different sounds and with headphones or by the jack outputs. Any idea or suggestion about what I can try or debug, or test what could be the issue? Thanks!