Tube Pre/ Class D Amp - Who has done it?

For Class D I prefer GaN FET. We evaluated and worked with several Class D amps in the past while designing our preamps but being a tube guy, we found GaN FET designs not only sound exceptional, but with their higher input impedance, they mate much better with tube preamplifiers than previous designs.  With other Class D modules, they were either too warm with no sparkle or they were sterile sounding and only good for bass modules  

Personally , I prefer the combination of a DHT preamp and a Hybrid DHT/Gan FET amplifier. 
 

In some cases I believe this is to allow for the OEM to produce their own high impedance input stage.  If you make pr eamps, maybe worth taking a gander at incorporating your own front-end. :) 
 

Thats what we have done with our Hybrids. 

That’s what we have done with our Hybrid amplifiers. One uses a DHT input stage. I didn’t want to go to far into that as didn’t want the post to look like a promo.