One of the cornerstones in Zenn Audio's philosophy is the strict belief that only triodes are capable of truly musical sound and the employment of pentodes and tetrodes are unacceptable compromise. Thu s where high power is not a requirement, a single ended triode amplifier is the best way to go. Such as a 2A3 for 3 1/2 watts, a 300B triode for 8 watts and a 211 triode for 25 watts. For higher power, the hybrid amplifier using triodes to drive mosfets ,which are solid state devices that behaves like triodes and can sound like one in  the appropriate circuit.

The Zenn hybrid amplifier is a forte of Zenn designs. Many years in the making ,culled from the experience of building many hybrids, one at a time. No two customed hybrids were ever identical. Each was listened to carefully ,evaluated as to why it sounded different. From this long, learning period was born the Zenn hybrid amplifier. It was discovered that for the hybrid amplifier to sound like a great tube amplifier,the tube driver stage was the key. It was found that for the mosfets to sound good , they needed a tube driver with very low output impedance ,that is one with lots of current delivery. In theory ,mosfets don't need much current to drive them due to their high input impedance , but in practice they just don't sound good that way. Thus the Zenn hybrids use a 6AS7 twin triode, which is a very low impedance output tube and often used in OTL designs. This tube is used as a cathode follower to drive the mosfets creating a hybrid design that is definitely more musical than amplifiers employing EL34s,6550s and other such non-triodes.

Another aspect of importance to Zenn hybrids is the use of the classic Pi power supply. This entails the use of a tube rectifier and choke besides the usual capacitors. This ensures a sound that is smooth yet transparent.

In the past , the few hybrids that were around were not only limited in their musical capability, they were also far from being reliable. And when they fail, they do so with fatal consequences for the speaker's woofers. One of the primary reason for this failure was often in the relay mechanism used in all early hybrid designs. They fail to protect the speakers from the large DC surges that occur in the tube stage when coupled to DC coupled solid state output devices. The Zenn hybrid employs a circuit that is so safe that no relay protection is used. Thus this removed the relay circuitry as the main cause of failure in a hybrid design. You can even switch on a Zenn hybrid amplifier first and then switch on the tube preamplifier. Doing this with an amplifier with a solid state output stage would be committing sonic hara-kiri.

Thus the Zenn hybrid amplifier sounds like a great tube amplifier and behaves exactly like one.