Eversolo DMP A6 with or without preamp

Maybe having both a Mac pre and amp was too much of a good thing?  Agree with maybe trying some new and maybe more transparent tubes.  Hard to believe you couldn’t significantly improve upon the preamp section of a $900 streamer/DAC combo unit either with new tubes or a different preamp altogether.  FWIW, and best of luck. 

All analog or analog outputs?

All analog outputs

I ran mine USB and then I switched it to analog directly into my MC 601s. I’d like a direct into my 601s better than going USB. It just sounds more lively, more dynamic I guess. I don’t think the differences in my head, there’s no way to a-b it.

I first plugged the A6 to an Anthem mix 510 via analog and thought it sounded real good.  

Today's digital gear ain't too shabby.   I just picked up a Cyrus i7-XR  Integrated Amp and I love that little amp.  It has a built in DAC and coincidentally it has the same ESS chipset as the Eversolo.   I can't believe how good my TV, PC , and Vault 2i sound with that little guy.    That said I'm not surprised you like how it sounds.   

Some Mac preamps and integrateds have an input trim setting. Personally I would start with the Eversolo' s output set to fixed or maxed out.  I forget how it achieves max output , but you want a fixed out equivalent to approx 2 volts like any other source component RCA. 

If you have it XLR , I would do the same as it should be about 4 v when fixed.  

Then with that fixed I would adjust the input trim plus or minus if so equipped