You should be incredibly proud of the work you’ve done with them so far. The Cascade by far the best digital sound I’ve ever experienced. I can’t wait to see what you come up with next! Bravo.
What a wonderful post and of keen interest to me as I, like most, consider ways to improve on my system. I rum my Cascade directly to my D’agostino Momentum 400M MxV’s with my Phono Pre going directly into the Cascade. Until reading your post I thought I’d put the preamp question way back and out of sight. As you say it’s not logical that it would make a difference except to add the Preamps sound signature to the mix (+other theories you list). What I’ve read about the 727 (which I almost purchased) suggests it’s an incredibly neutral Pre. That nag is now reestablish.
Using the Preamp function of the Cascade DAC adds no stress or work to the DAC portion. The Preamplifier is purely passive so there is no extra load on power supplies or any other circuitry.
Thank you. That was my understanding.