Why do our Fet Valve amplifiers have such stunning audio performance?
Three basic reasons.
First, because these are unique audio designs, unlike any other amplifiers out there. They could be considered to be elegant single ended Class A tube amplifiers followed by ultra fast and powerful current amplifiers with very low output impedances.
Second, because each separate active device section has its own independent regulated power supply. There are independent regulated power supplies for each plate of each tube, for each small signal power mos-fet in the transimpedance section, and for each output current amplifier section. In addition there are even separate regulated power supplies for each tube heater. This means the amplifier remains rock solid under dynamic transient conditions and plays all the music exactly as demanded with no mush out from supply rails moving because of high current demands.
Third, these amplifiers are uniquely designed for unconditional stability. Every node has a Q of 0.5 so there is no possible ringing or transient overshoot under any condition. Every power supply feed, every audio feed, and even the ground feeds are critically damped. This allows complete use of the awesome speed of the Exicon power mosfet output devices and a real power bandwidth -3dB at 4Hz on the low end and 350,000 Hz at the high end. No transient overshoot means no mud and no rough edges. In addition absolute stability provides superior fault tolerance because transient overloads do not generate excess component destroying heat.
The end result is the lovely musicality you have noticed. You are not alone. In addition to Jim Salk and Dennis Murphy, David Janszen recently acquired two Fet Valve 400R amplifiers to drive his Janszen electrostatic speakers at consumer trade shows. His room got a best sound rave report from one international audio publication at the recent Munich, Germany show where he was using the 240V version of the Fet Valve 400R.
Frank Van Alstine
