I don't know if this is typical of all 2488 units but mine has always had a faint high pitch whining sound. This sound also breaks though as electrical noise on the Guitar (H) input when using a high gain effect. Anyway I decided to track down the source of the whine. I thought that it was a vibrating inductor or capacitor in the power supply but after careful listening it seemed to be coming from behind the LCD screen. So I tried disconnecting the LCD screen and the noise was gone. Then I reconnected the LCD, disconnected the power wires for the electroluminescent backlight, and again the noise was gone. This means the problem is related to the EL panel in the LCD screen. Since I have a HGR 2488 VGA Monitor kit installed I don't really use the LCD so I cut the A & K wires that provide power to the EL panel. This means the LCD no longer has a backlight, though it is still readable in a well lite room . Anyway this may be of use to anyone else who experiences the same problem.