In short: q) is it worth the money? a)yes, absolutely.
A while back John repaired the Trivista DAC, and since then I’d lurked here, reading upgrade reviews, wondering if there was something in it….
A series of unfortunate events led to the heart of my system (inc the DAC again) going to John for repair and I decided to go for the upgrades.
I can concur with most if not all that has already been written here about the improvements. For me massively improved timing was the first thing, drums now lead the way, rather than feeling a bit behind. But the improvement in the bottom end is most noticeable thing. A large room and a large subwoofer should mean bass heaven, but there were times when chasing the deep extension meant a bloom or overhang. That has gone, and now total control, total authority and a deeper bass puts a big grin on my face. At last my sub is doing what I had always hoped it would. Elsewhere there is more detail at all frequencies, the top end is blessed with a finesse that is at times jaw dropping, making everything a more interesting listen. What is remarkable is that none of the MF Nuvista traits of ‘grain free’ and ‘liquid’ top end have been lost. There is just more of the MF goodness flooding through. As others have said, John is a craftsman, an artist, a fascinating man and a nice guy to chat with when he has a few minutes, and to that list I add ‘miracle worker’ for making what I thought was a pretty reasonable system loads better.