Hello, I am totally blind and recently baught a used Ameritron als 600. I baught it for its no tune capabilities and ease of use for a blind person. However, I have a few specific questions that would not have to be asked by a sighted who could read the manual, so please excuse me. First, I note there are two controls for alc, one in the front, and one in the back. how do they differ, and how are they used. I also found out there has been an update to the power supply. What is it, how would I know if my amp has it installed, and if not, do I need it? I am using the amp with a kenwood 940. Thanks and 73'es. Joe.