Listening to these exquisite old Moody Blues arrangements, I find myself beginning to wonder if the Mark II amplifiers and speakers have any kind of a natural high-frequency rolloff. I find the keyboard balance of my 400 doesn't seem to sound the same as the Mark II, where the high notes seem a bit quieter and also a bit more filtered and softened than the low notes. Has anybody else noticed this and tried working with some lowpass filtering on a 400 to see if it sounds more like the Mark II?