Hi Paul,
Is it true that you have abandoned the Tripath chip for future amps in favor of a discrete (FET) output stage?
Yes - future designs will feature a Class A tube input stage, and a discrete FET output stage, along with our OEM designed LiFePO4 battery power (we have also abandoned SLA batteries as of the Fall, 2010).
but why didn't you just go that way to begin with? It's not like this is new technology. Was there a reason for this 'philosophical' shift? Was the motivation the sonics, or something else, etc?
Not a provocative question at all --- From 2005 into 2010, for amplification we used SLA battery power and Tripath, with excellent results. When we switched to our LiFePO4 battery packs, it opened up a a new door for us, allowing us to add in a tube input stage. The LFP-V Editions outclassed the older SLA / no-tube products in many respects (sonics, play time, battery longevity, higher energy density and current, etc.).
With the LiFePO4 battery technology and tube input stage we decided to experiment with discrete Class AB FET output stages, and combined with the tube input stage and all powered on LiFePO4,
we moved into another class in sonics!

See:
http://www.6moons.com/audioreviews/redwine14/2.htmlI am quoted a lot in this page and it explains all of this and more regarding our 'philosophical' shift.

Thanks for asking,
Vinnie