My Dad has one connected digitally via USB to his Mac 8950 and it sounds great with the Mac DAC 2 card doing all the heavy lifting. Yours is all analog so I am surprised to hear you say it sounds better with no preamp.
Maybe time for new tubes?
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.
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
I have gone back and forth with trying dacs straight to amps, and with preamps. Straight into the amp always sounds different, not necessarily better, depends on the dac . Some will sound good at first, then you realize it doesn't really have the drive a real preamp provides.
So a dac needs a good preamp section, which a lot of cheaper dacs doesn't have.
Shocker. That’s exactly why I recommended trying some more neutral/transparent tubes. You can play with wires and tubes if you want, but it sure sounds like too much thick Mac syrup in your system and the A6 is giving you a needed dose of transparency and fresh air when combined with your amp. If you can, try something like an ARC, Linear Tube Audio, or Backert tube preamp in your system and you may be very positively surprised as they’ll all offer much more than the A6 could ever hope to as a preamp — as they well should. I think the A6 gave you a small glimpse into the improvements you could have in store, and I’d recommend pursuing that further as there’s clearly (pun intended) something there.
Trade in the C2300 for a digital preamp. I have the MDA200, it has the preamp section from the C53, and it sounds wonderful straight into my 7270.
I prefer a dac/preamp combo with separate streamer, as compared to streamer/dac with separate preamp.
You can get the MDA200 for about the same price you can sell the C2300 for, and it has the latest D2 dac.
eyelai777, your experience makes sense. If a source such as your Eversolo streamer has a variable output with sufficient voltage and current, then you can drive an amplifier directly. This eliminates interconnects, contacts, potentiometers, capacitors, gain stages (tube or SS), and power supplies that can only get in the way.
Of course, we audiophiles often have multiple sources (e.g. discs, phono, tape, radio) so a pre-amp is a convenient way to select, buffer impedances, and control gain/attenuation.
Your Mac pre-amp should be close to transparent. I recommend setting the Eversolo output for bypass and re-evaluating. It's possible that "analog volume setting to max" in variable mode may not be the most linear or noise free condition.
If the sound is still "veiled" then you could experiment with premium tubes as suggested by another post or explore other solutions if you choose.
I have not used the eversolo before. I would say that it depends on the output section of the Dac. I used to use a dCS Bartok straight into an amp and it was good. I have since moved to MSB w currently with the premier Dac and s202 amp. There is synergy there as they are designed to work together. MSB dacs are also designed so there is enough output coming from their ladders. This eliminates the need to boost the signal at the output stage. The implementation of the volume control is really important too.