If I was smarter... I wonder if there is a way to record headphones in a mic. I have a Scarlet interface and a SM57 and 58. Like, play the same piece of music through each channel and record. Just to have a baseline, so when you make a change you can record again and listen. Take a picture of all the dials on all the equipment.
The recording wouldn't be representational or what you are hearing, but the differences of future recordings and the original would at least tell you if you are succumbing to madness. If you're not already insane for doing all this in the first place.
So if the original and the changed, sound the same, then you changed, not the device. I don't tend to remember the exact sound anyways, just how it made me feel at the time. And I didn't do this experiment. But it does make me wonder.
Even if you did all that work, and you discovered there was a change, or no change. Probably, You'd still want to change it to get something more... that's probably why you did the Speedball in the first place. And Bro, trust me, I feel ya. For me, the Crack was such a revelation, that I wanted to take it farther.
I would suggest listening to another device on headphones, then the Crack, then figuring out what exactly you want. More Bass? More Treble? Definition/Clarity? Midrange warmth? What would really ring your bell, and then ask how to attack that specific question.
