Whatever happened to Tripath?
I can't speak about Tripath directly, but I can about Cirrus Logic.  I used to work for Cirrus, and I know the guy who invented their Class-D technology.  They certainly did not get their Class-D stuff from Tripath.  In my opinion, their Class-D stuff is superior to what Tripath was offering.

After I left Cirrus, Tripath tried to sell me on their technology several times.  But I never got the impression that they knew what they were doing, technically.  It seemed like they were more of a marketing company than anything else.  Either that or their entire business plan revolved around getting bought by a bigger company.  But this is just pure guess-work on my part.