Denon ds1 thru mode much quieter than serato line level

hi im just checking if other people with DS1 have similar issues. if i play the same track from serato, and then from vinyl using thru mode, there is an appox. 10db difference (i would expect a slight difference between vinyl level and line level).

I would have thought that the levels between serato tracks and thru mode (normal vinyl) should be similar since they are both coming into the dj mixer as line level. It seems like the phono preamps in DS1 arent loud enough.

would appreciate if anyone experienced with using the DS1 with both serato timecode and normal vinyl records could comment on their experience.