The infrasonic filter was a particularly useful feature of the phono preamp. He also offered instructions on how to build an external buffer circuit to use with any phono preamp, to avoid cartridge impedance interaction. He sent out a letter with the circuit, and even included a pair of low noise transistors - for free! As I did for the Advent Speaker ads, I`ve tried to recreate
some of the original model 300 materials from photocopies using Quark Express and my digital camera.