Here is what SPL has to say in the Phonitor 2 manual: I actually leave my Phonitor 2 on studio level all the time since I have an external device (Sony TA or Focal Arche) connected to the RCA inputs. Try it and see if it makes a difference for you.
.
RCA input HiFi level / Studio level
If you connect a HiFi audio device (e.g. a CD player) to the analog
RCA input
(18), you can amplifiy the signal from
HiFi level to studio level with DIP switch 3.
The sources are then equal in level when you switch between XLR and RCA (provided that a studio signal is pres-
ent at the XLR input).
DIP switch 3: ON = The RCA input is boosted from -10 dBV (HiFi level) to 0 dBu (studio level)
Yes it made a substantial difference in volume (positively) and sound quality (negatively). IMO on the Phonitor E the DIP Switch 1 (gain) only impact volume levels but DIP Switch 2 impacted volumes and sound quality. For me Dip switch 1 to +22db and Dip switch 2 to -10dBV is the optimal setting.