I wouldn't necessarily say its "innovative", but it is somewhat unique and different from the typical cathode follower tube OTL designs out there. Here is a blurb I copied from an email from Craig when asking him about the design concept of the Zana:
"There are three factors that determine the sound of an amplifier. The amplifier topology, the power supply, and the quality of the components used.
The Zana Duex topology is a single ended class A OTL design. The output tube is the 6C33C-B power triode, chosen for its low plate resistance, and high current capacity. Most tube headphone amplifiers use cathode followers in some form or another. By definition a cathode follower is a 100% feedback device which has less than a gain of 1 and a low source output resistance. Cathode followers share a sonic signature which can be characterized as large, thick, and even mellow. Some describe the sound as tube like. The 100% feedback also tends to make the amplifier sound compressed. A more musical solution is to take the signal from the plate circuit. This has the disadvantage of having a higher output resistance, but better sound if the load is much larger than the plate resistance. In the case of the 6C33C-B, the tube is biased up for a plate resistance of about 90 ohms. With a small amount of global feedback the source output resistance will drop to about 12 ohms. This is a low enough source resistance coupled with the high idle current of the 6C33C-B to do a better job driving headphones than most cathode follower topologies. The Zana Duex uses the 6SL7 dual triode for voltage gain and to bias the 6C6C33C-B.
There is only one coupling capacitor per channel, and that is the output coupling cap. Every capacitor has a sonic signature. The coupling cap for the Zana Duex is custom made, and the best available for this topology. It uses three dielectrics, paper, polypropylene, and soybean oil.
The last element in the equation is the power supply. Because the plate loaded triode, SE, OTL topology has a very low power supply rejection, one could say we are listening to the power supply, or at the very least the power supply contributes to the sonic signature. The ZD uses a classic passive RC, LC, LC filter per channel. High quality film capacitors, and 4 power inductors make up the basic power supply providing clean direct current to the output triodes. Because of their high output current capacity, and slow turn on characteristics vacuum tube damper diodes are used for the AC rectifiers. To further minimize sonic attributes caused by magnetic fields the power transformer is outboard, and the Zana Duex chassis is made from aluminum."
