he Khan Audio VTDI is a faithful re-creation of the classic SVTDI all tube direct box. It utilizes a single 12AU7 in a unique 2-stage design that maximizes both the harmonic richness of the tube as well as powerful low-impedance output drive capability. The VTDI is ideal for use with a number of instruments and sources including bass guitar, acoustic instruments, keyboards and synth modules. Power it down and the VTDI automatically goes into passive mode. This handy feature allows it's use as a normal passive DI as well as a high quality tube DI.