Class A output stage for CD Player


I have an Harman Kardon HD750 HDCD CD Player and i want to modify the output stage. This original DAC is a Burr Brown PCM1732 one bit with a NJM4560L op amp. I would change the NJM4560L by a AD825 plus a class A output stage (tube or not) or directely replace the NJM4560L by a class A or valve output stage.
This is not a great problem with "standard DAC" but The only problem i have is that PCM1732 have HDCD Gain and i don't want to make a mistake.
Does somebody have an idea how to do ? and where i can found a class A output stage schem for this type of DAC ?

Excuse me for my english, I'm french.