I have an Alverez Fusion Series acoustic electric with the Alvarez Series 500A preamp installed. I have been looking for a new preamp as this one no longer works. I can only find the new System 600T Mk II. I would like to know if anyone knows where I can purchase the original preamp (it is no longer in production) and/or how difficult it is to change it to the new preamp. I have been told they the dimensions of the two are definitely different. Any help would be greatly appreciated. Thanks.