Could Class D really be that good?

All op amps have an intrinsic sound.....and how you know this is to listen. There is no monolythic integrated circuit IC (that I know of) that sounds as good as a really great discrete circuit. This is from testing (and designing and making my own) op amps for 25 years. If you have an integrated circuit op amp......you need to upgrade it. So, which discrete op amp sounds the best?......I personally like the LKS and the modified Sparko Labs 2590 the best. When I was modding Oppo 205s I changed the stock 4562 to Sparko 3601 but then went to the LKS (I had modded the LKS DAC so I knew those op amps were probably really great). When I saw them for sale on line I emailed LKS and they sold some of them directly to me. They were much better than the 3601s....Of course, I removed the connectors on the opamps and soldered my own 6n copper leads to the op amp.

I find the Weiss very detailed but lacking depth and musicality. The Sonic Imagrery, and New Class D too transistory sounding. I have not listened to the latest Burson or the Staccato, and I am sure there are others that might be better.

Adding a tube buffer will ADD tube sound. That is what it is for. It will not measure as good, as no tube has the low noise of a great op amp. The tube buffer in the VTV has an op amp after the tube.....so it really is just adding tube sound. Warren at VTV loves how it sounds. It is his reference. He uses the stock 2950 as the op amp on that board. Warren has never heard any of my mods (to the op amp or to his amps). If you are buying the tube buffer it is because you want tube sound....not for its measurements. Tubes add liquidity, space and palpability.....they make for a more "musical" sound. I personally think that if you want a tube in your system.....that it be only one. Too much tube sound makes it slow. This is why people like a tube preamp with class D...or other solid state ammps. A nice combo. I tweak my whole system enough that even without a tube I get very musical and revealing sound. Most people do not know how to tweak that well so a tube piece of gear is a nice way to get to heaven.

The Nilai amps have built in buffers and regulators....so the only tweaks you can do is to mod the output filter caps and change all the wiring and jacks and damp the chassis (yes, it is a worthwhile improvement).

Yes, the amount of distortion and its spectrum has some correlation to sound. However, it is not the major or only thing that makes and amp SOUND the way it does. You can give me 3 pairs of Atmasphere amps and I will change some of the parts in one to really bad sounding parts.....leave one of them stock and in the 3rd one I will change a bunch of parts and execution that I know will make the sound better. They will still all measure the same. Ralph or anyone would be able to pick them apart..........even on a double blind test.

When you change parts, you change the distortion so the sound changes. This is easily measured and correlated to what we hear. So they would not measure the same. Distortion is literally the sonic signature of any amplifier.

Did you not read what I said?  I said the amps will all measure the same.....this is absolutely true.  While it is true that when changing parts the distortion changes....because all noise and veils are distortion.  However, you CANNOT measure a change in measured distortion when changing passive parts.  I can hear the difference in 2 inches of wire.....try measuring that!  We have been down this road many times.  You are one of the few people on the planet who BELIEVE what you just said.  Again, you cannot measure the difference in distortion by changing passive parts, damping, fuses, cables, etc.....no way Jose!  Lift your cables off the floor.....you get lower distortion....try measuring that!  Try removing the steel plate and bolt off your toroidal transformer and raise it off the chassis with a one inch piece of wood and be amazed at the sonic difference....try measuring that.  Please, come over to the "dark side".....it is way more fun than re-stating the same BS.  You will learn a lot and your products will get even better and you will make more money.  A win for everyone.  But many will take their "opinion" to the grave.....It is called being "dead right".  I am wrong many times.....I change my mind....it is fun....it is an ever changing game....infinite and full of surprises.....I learn new sonic things most every week.

I definitely have no experience with op amps but believe in their ability to change a piece of equipments performance. After building the Nilai the first things that come to mind are wanting to upgrade the jacks along with internal dampening. The caps could be a major hassle due to space..the wiring not so much.

As much as I love the beautiful inaccuracies or pleasant mild distortions/coloring of tubes I do appreciate low noise linear solid state gear as well. I pulled a tube pre off the Nilai yesterday and enjoying now straight from dac. With certain music I prefer the visual perceptions I can get from tubes and a clean power amp. Kinda funny how I strive to find & appreciate an amp like the Nilai due to its engineering and impressive specs & then look for different ways to add changes to its sound. Not with just passive parts. 

Whilst Discussing OP Amps, the OPA 1656 is one known to be selected for use in place of other OP Amp's.