Did the stock cable on the Vega need some kind of Burn-in ? Because actually, im using my Fiio balanced cable that was on the Fiio F9, and the mid are more clear and the bass is tighter... from a AK70 balanced...
The stock Vega cable is single ended (3.5mm) - if you were using the balanced cable from your F9, you will be comparing the balanced output of the AK70 to the single ended output, and that will potentially be different in terms of power, crosstalk etc. That may be the source of the differences?