ProD8

From Radial Engineering:

The ProD8 is a high performance 8-channel passive direct box optimized for keyboard rigs in professional touring, with redundant 1/4″ inputs for each channel and a completely passive design that requires no power to operate.

The ProD8 features up to 8 direct box outputs in a single 1RU rack space for professional touring, with dual ¼" inputs on each channel to incorporate a backup system or connect up to 16 channels of audio at once. A ¼" TRS effects insert jack on each channel allows for connection to various effects devices while adding greater routing options, while a thru-put jack delivers a direct feed to the artist's playback system. The front panel features isolated XLRs for balanced low-noise outputs, each equipped with ground lift and 180° polarity reverse switches.

The engine inside the ProD8 is a custom wound Eclipse ET-DB2 transformer that performs both the impedance matching and balancing. Linear from 20Hz to 20kHz, it is able to withstand the extreme dynamics common with today's digital keyboards. Unlike active circuits that overload and square wave when the rail voltage is exceeded, transformers saturate. This means that as the signal increases, the ProD8 naturally rounds out the tone producing a warm Bessel curve reminiscent of the very best vintage audio gear. The other significant advantage to this passive design is 100% galvanic isolation between the source and destination, which eliminates hum and buzz caused by ground loops.