So PC-software-DAC-amp brings up the question: what software/volume control to use to play PC files. I only experiemented to simply find the volume control/software that allows the highest output (amp input not sensitive enough). Didn't consider quality (and haven't concluded yet on easy of use regarding software choice).
Paul McGowen (PS Audio) got me started on this whole idea. He pointed out how a volume control is a restrictive device. Restricts resolution. Like putting on the brakes in a car. He said you should get the volume knob as high as possible so it does as little damage as possible. He said he likes the volume knob UP around 2 to 3 o'clock position. He said the higher volume position has a "HUGE" impact on the resolution/sound.
How the heck can you accomplish this volume position? This led me to use the Audirvana software using a 64 bit high quality controller(Roon also). This allowed a higher position on the preamp volume knob BUT now I was using two volume controllers. So now... lets eliminate one. Get rid of the worst and use the best and most simple.
It's possible that the reason a straight DAC sounds better than a passive preamp is the complete elimination of the restrictive volume control.
I also think people are fooled when they hear a preamp that has a boosted gain. The more dynamic sound is immediately noticeable but at what cost?
I experimented with a Melos tube preamp that adds 20db of line gain !!! Had a big sound with plenty of dynamics. "A fun sound". "Big and Blowsey" (as per stereophile) Couldn't get the volume knob up past 9 o'clock. Way too loud. Having high resolution music source then restricting the resolution with the volume knob seemed counterproductive.
FYI... higher end preamps use better quality 'digital volume controllers' or 'stepped attenuators' to deal with this problem.