There is more to any piece of electronics than the inclusion of a tube. This is true with preamps, CD players and amplifiers. Just because somebody has a tube in their electronics doesn't make it "good". There are huge issues involved that go way beyond the inclusion of a tube. I can easily identify a few of them. There is regulation, component distortion, parts quality, bypassing.... and much more that is way over my head. Nonetheless, the basics that I do understand provide a very good basis for indentifying electronics quality on paper. I offer this for a couple reasons.
1. I am sure that guys who really "know" simply roll they eyes in dismay when folks seek a particular piece of electronics because it has a tube. I believe Frank is one of these guys.
2. There are some VERY good CD players (i.e. Wadia) that performed great and didn't have a tube.
3. I suggest you try to discern quality with your ears whenever possible. Choose a good symphony recording and listen, listen, listen.
4. While I own a well regulated and slightly modified Anthem CD-1 (it has a tube), I think Frank's DAC is darn good too.
As you explore this, I suggest you call Frank on the telephone and ask him about his DAC. It seems expensive, but there are reasons for this. Sometimes it appears that better quality is available at a cheaper price... until education happens.
IMO, Frank's amps are killer. I have "popped the hood" and found very good reasons for this. There are extremely high quality parts implemented very well - IMO.
Please consider that I only repaired electronics for 3 years, and I have only been building speakers for about 7 years. As such, my word is NOT the last word when it comes to these things.