@maprik
I do not know the Merason DAC but its reviews stress its musicality. Its USB interface appears to be first class so changing your streamer (or anything else upstream) probably won't help. AES will probably sound worse as you are then more dependent on the A6's clock which is good but probably not as good as the Merason.
Upgrading (that may not be the correct word, given the quality of yours) your DAC to (e.g. EMM Labs) would cost you to $30k+ and still might not do it.
Your Tim de Paravicini phono stage is legendary for its lush musicality so you may never get the same type of sound - unless perhaps you switched to a tube pre-amp. Are you using the Hegel as an integrated? You could try a Cary SLP-98 (you get 30 days approval on a standard - non upgraded one.) If that went too far with the analog use the Hegel's pre for analog, and the Cary's output into the Hegel's main amp input.
The phono stage is a strong contributor to what you are hearing, as an example when I switched to a Sutherland Dos Locos from the Duo there was immediately more "there there", resolution, sound stage, musicality, richness, dynamics. de Paravicini was a genius and you are hearing his magic.
Switching to Cardas Clear Reflection from DAC to amp might help, that cable is on the warm side without losing definition.
Weird thought - try the DSP EQ system perhaps? I have a T8 and there are a couple of old 44.1 16 bit recordings where I knock down the excessive top end with EQ. Generally I do not use it.
I think I have accepted that LPs and Digital have a different signature, LPs have a warmth and depth, great digital has a wonderful clarity and precision. Generalizing, (and others may disagree) LPs put you in a sweet spot in the concert hall, digital gets you in the front row.
