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.