High end Class D amps?

tweak1:
" I have owned many different class D amps for over a decade. A few I would say would have benefited from a romantic tube somewhere in the system, BUT, D has gotten much better, especially in the high freqs, to where, IMHO, changing cables would be the better option. The Cable Company would be a good source to try a variety of cables

I have a Tweakaudio EVS 1200, which uses the same IcePower AS1200 modules as PS Audio M1200, but are highly tweaked by Tweakaudio. No tubes anywhere in my system, and it's very detailed without being edgy"

Hello tweak1,

     You made a couple of excellent points I can tell came from personal experience:

1.   Class D, in my experience, is so accurate and neutral that it facilitates the perceptions of how changes upstream in the system effects the overall system sound quality.  This applies not only to more significant  system changes, like the source components and the quality of the recordings themselves, but also down to smaller changes like in the ics and power cords utilized.  In my opinion, this qualifies as very high quality transparency.

2.  I've come full circle about my thoughts and perceptions of combining tubes with class D amps.  I began by using a VTL 2.5L preamp with an expensive set of 4 NOS Mullard tubes swapped in for the standard Russian or Chinese ones.  I used this for several years with my class D amps and liked it so much I thought  I'd never take it out of my system.
     But I happened to hear a Mark Levinson 326S ss preamp at a local hi-end shop.  I was so impressed with its performance, especially the amazingly real stereo sound stage image it presented, that I bought a used one and tried it out in my system. 
     Well, the midrange and treble sounds just as sweet and euphonic as the VTL with NOS tubes and the palpably realistic stereo sound stage illusion the ML presents was just too good to resist.  So, I sold the VTL to a friend and I haven't regretted it since. 
     So I've come full circle from thinking I had to have tubes somewhere in my system to discovering that my system without tubes can sound even better.  The only qualifier is that it took a very good and expensive preamp to top the tubed VTL. 
     My current opinion is that tubes combined with a class D amp usually results in very good overall sound quality. But I also agree that the quality of the midrange and treble performance, on good quality class D amps, has generally improved to such a degree that tubes may no longer be needed.  As usual, it'll probably come down to the specific and unique amp/preamp combination utilized.

Thanks,
  Tim

I'm no EE but the board's "wiring" or circuit path into the Sphynx's modules seems infinitely less complex than what's going on in the Dragon board's circuits going into the Dragon's modules.

If you look at the photos of the Dragon the hypex module plugs into the board the same as any other input buffer board. The tubes are not inserted into the hypex board and the input buffer board doesn't look anymore complex, that's not to say something in the buffer board could be different but the tubes in no way are inserted into the hypex, it's marketing speak for look we added distortion to a perfectly good amp. 

djones51:  I don't think that "insert" has to be literal!  There is a myriad of pins on those modules that likely allow for other configs.  Did you read any of the interviews provided or any others out there?  I don't have a dog in this hunt, I'm just asking if anyone has any experience in comparing Rogue's basic tube buffered input style to their TubeD designs.  As I've said, I live in an audio desert and shipping amps around gets kind of expensive quickly.

From Dagogo - MO: What is really exciting to me is that these amplifiers are much more than just a tube circuit in front of a class D circuit. We use only the modulator and mosfet output stage, and bypass all of the other circuitry on the amplifier modules we are using. We actually combine the tube and buffer stages with the output section, using proprietary circuitry that makes the output section perform like a tube stage rather than solid state. What is quite gratifying is that we have had numerous class D naysayers wind up purchasing them.

From Positive Feedback -  So I built what is a basic Hypex-type amplifier, as that was the baseline on one side; and then I guess our top-of-the-line Apollo mono-blocks were the design goal on the other side. I never started off to make a pure digital circuit; I just built one without the tubes in it—though I knew that wasn't what I ultimately wanted. But I wanted that as base line: like, okay, here's what the Hypex Modules sound like used as they were designed to be used, to build the same kind of digital amps that a half dozen other companies out there are building with the Hypex Modules, the big difference being that we only deploy the switching MOS-FETs on the output section of the modules and otherwise we bypass everything on the modules that Hypex supply that everyone else uses—we are not using the Hypex Modules' driver stages or their input stages.

Seems pretty evident to me that unless a respected and accomplished guy like M O'Brien is really being evasive, exaggerating or such, there is a decidedly different implementation of the tube portion and use of the Hypex modules, in those amps.

Lastly, I really don't care about the details and as it's been stated, likely correctly numerous times in this thread, it's all about the implementation details. This would seem to be a different implementation.  Just asking about experiences of any audible differences within the lineup, due to this implementation.

While not Class D, check out the Cherry Amps which are digital.

https://www.cherryamp.com/

@grk, Tommy's Cherry amps are Class D.