Back when there were few choices in 500 Series preamps, people really appreciated the many permutations offered by our DIY500 template. For those who were not DIY-savy, they'd write with a specific request and Jens would create a custom preamp module trying to address this request. Each one was unique, built-to-order, and assigned a serial number (EAC###) and a brief descriptive name. This series came to be called "Eisen Audio Custom". The service lasted from 2006 through the end of 2010 when we discontinued our DIY500 product. Dozens of different modules were made, including a limited edition of fifty EAC312V. A few examples are pictured below.