The PDI-01 D.I. box is a passive unit that works exceptionally well in almost any standard application. A specially designed high quality balancing transformer provides smooth frequency response throughout the audio range, huge amounts of headroom, and maintains signal integrity. A rugged diecast alloy box provides excellent RF shielding.

The SOFT GND feature is new and exclusive to the latest version of the PDI-01. The two grounds are not directly connected to each other, but instead are connected through a capacitor to form a "soft" ground. The reason for this "soft" ground is that many computers and other equipment radiate high frequencies that have a very disturbing effect on the signal, which can be heard as a high-pitched buzzing sound. This can be eliminated by grounding through a capacitor, which, due to an adequately high resistance, also takes care if the normal 50/60Hz AC hum. The SOFT GND should be used if the PDI-01 is connected to a computer sound card or interface device.