Sony and Yamaha, back in the 70s, were the very first to offer VFet amps and preamps. Sansui and JVC too offered VFet power amps, which are very rarely seen today! Until Nelson, came out with his SIT line, no one else in the American and British high end clan, even went near Vfets! 

I have read that John Curl, in the late 70s, was to design an amp for Gale with Vfets, but this amp never became a reality. Today, aside from Nelson, there are two Japanese companies offering VFet amps and they are: Digital Do Main, using NOS Yamaha devices and Moxite. I know not where Moxite is getting their Vfets from. I seem to have read somewhere, that the Holcro amps too used Vfets, but I have no way if confirming this. In the pro audio world, the brilliant John Mayer, makes VFet amps to direct drive his outstanding speakers. Again, I know not where John gets his Vfets from either. Nelson had is SIT devices custom made! One or both the Japanese companies mentioned, have been making Vfets amps longer than Nelson.

In the 80s, a company called Thunder, made very sophisticated amps for cars, with Mosfet switching power supplies and N channel only, VFet output stages! Not everything that advances the audio art comes from the high end! A Sony Vefet integrated can be had for 400/500$ and very well worth it! You need to have the diodes in the output stage replaced. The net has the pertinent info... 

The Yamaha is an expensive proposition, as they did not make integrated amps. Their B1 power amp and it's matching pre and the later B2 and it's matching pre were top dollar affairs and to this day are highly sought after. In the beginning, Yamaha did not, like Sony, have complimentary device and thus the B 1 is not fully complimentary. Many believe the B1 is the amp to get, but I can not give a recommendation, as I have never heard a B 1 nor for that matter, a B 2! However, I have owned the top Sony VFet power amp and I would sum up it's sound as "visitations from the heavenly abode"! 

In the early 80s Sony introduced the prestigious Esprit line of extraordinary audio gear. In this line, they offered the worlds very first PWM power amps. There were two models and they both used Vfets as the switching devices. Of these two amps, I have heard the lower powered model. Again, outstanding sound! Go on the First Watt web site and read Nelson's prose and see the pinch curves of SITs and triodes! Very enlightening! Audio bliss is at hand with Vfets! - Kavi Alexander