This is my dream amplifier a S. S. one it is the top version of my Alpha 607 i :

Sansui Alpha AU-907MR

https://www.youtube.com/watch?v=Pa2Y95eQjNA

@michaelalan 

Yeah...if it ever happened I would most likely keep my tube pre. Can  you tell a diff between class D and A?

@oddiofyl 

Ever try the QS AT7?

Never tried the QS preamp,   my last preamp was a CJ Classic 2SE which was an excellent sounding preamp.  Before that a McCormack RLD 1 , a McIntosh C15 before that.  Looking back after using that Zesto for about 10 months they were all slight improvements over each prior but nothing like the Zesto.  In comparing the CJ to the Zesto it was not even close.   It was as if all previous preamps were a bottleneck.  

After fifty years of pursuing the high end… the first forty with solid state amps.. I will not go back to solid state. I found that tube amps can be incredibly reliable and more importantly musical.

When I was working I put about 600 hours a year on my system. That would require retubing about every five years.

I now listen a lot more and have replaced four tubes in the last three years, one DOA and three at normal maintenance time.