The DI503J is a triple mode Direct Box for instrument and a Re-Amp unit for the '500' format of API*.
The DI offers a Passive mode based on a Jensen transformer, a FET mode and a Tube mode. It also include a low noise, low distortion preamp for a line output.
The MC624 is similar to the monitor section of a mixing desk: it lets you select one out of six stereo audio sources, adjust the level and route it to one of four monitor outputs.
