Discrete R2r With Tube Output

the aqua hifi lascala would do it

https://6moons.com/audioreviews2/aqua/2.html

pure r2rdesign

plays high resolution files

incredible analog stage

modular and upgradable

Dave and Troy

audio Intellect NJ

aqua hifi dealer

I have the Lab 12 DAC 1 Ref.   It really sounds good.  Something that should be auditioned or have an easy return policy.   I listened to a few DACs below , at , and above its price.   Loved its sound and can live without DSD and fixed output. Which I prefer on a source anyway. Not for everyone but a really nice sounding DAC. 
 

Maybe DSD is why he wants a FPGA type DAC….

The Wells Audio Cypher Dac is fantastic and uses the latest Sabre pro dac chips.

good luck on your search.

@glennewdick 
I just got that LTA Aero Dac and its incredible. Excellent resistor chip and there's no beating a David Berning tube stage of power supply.

Lampizator