\rHi Robert:
The Pre-1 is a nice addition adding additional switching options for the AMP300. But it is not mandatory. The Pre-1 is good if you have a Turntable utilizing a Moving Magnetic Cartridge since it has a phono preamp not found in the AMP300. It also has a tape loop for adding an Equalizer, 3 other inputs, a Mono Stereo circuit, Bass, Treble, Midrange, and Loudness contour switches. It also features a 1.5 MA additional gain. Just a little more control for a pure High Current Amplifer that already has automatic Source switching between Line 1 and Line 2 inputs.
TimL/OSD Tech Support 7/13/2021\r