Upgrading digital source device is not easy

I see.
Then please recommend DAC for me.
My music collection is mainly classical and Jazz

thank you for suggestion

You may want to check out the NEW PS Audio Direct Stream since they announced another firmware (or Operating System) update yesterday.

"PS Audio's digital guru Ted Smith has been busy during the six months since the release of the Huron OS, announced at the time as "revolutionary". How do you follow a revolution?

You get to work. By diligent effort Ted has managed to improve upon Huron, the best-sounding firmware PS had ever released. The new OS, Redcloud, improves upon Huron's already-exemplary spatial presentation, dynamic contrasts, and low bass. By better-linearizing low-level signals, Ted has managed to reduce residual noise and THD even more, with startling improvements to low-level resolution, ambient hall sound, and solidity of bass performance. Blacker backgrounds, immediately-identifiable concert venues, and incredible dynamic slam are all evident with Redcloud.  

As good as Huron was, Redcloud is far better. The improvements are immediately noticeable---as Paul McGowan put it, "it's a 10-seconder. You hear how much better it is instantly."

A used PS Audio DS can be upgraded for free to the RedCloud update. This thing also has ROON support via the Network Bridge II card. This unit is likely my next DAC.