The Thermionic Culture Robin DI Box is a very simple box, but rather special in terms of quality and application. It features a 10:1 ratio and input impedance is 100x the input impedance of the mic amp, so a mic amp with 1kΩ input impedance means that the transformer will present a 100kΩ load to the instrument. The frequency response is flat over the audio range and there is no measurable distortion added by the unit.
Features
No solid-state transistors or ICs so NO 48 V power is required
Phantom power to The Robin must be OFF
High-spec transformer (E.A. Sowter) to match impedances
Bypass switch so that the transformer is out of circuit and you connect directly to the mic amp input - this works well with the Snow Petrel as it has a relatively high impedance input
The amp jack is connected directly to the DI JACK for a separate amplifier to be used
Earth lift disconnects the ground connection (Pin 1 of the XLR output) from the circuit in the box to prevent a hum loop which may occur if an external amplifier is used or the instrument is powered from a grounded mains supply
Switch guards are provided to protect the switches from possible damage and the box is of very rugged construction