DDJ-RB output levels

I've recently bought a DDJ-RB and DDJ-SB2 to decide which of the two I want to keep. Overall I've been very impressed with both but given my preference is now to use Rekordbox over Serato I'm thinking of keeping the RB. However what struck me when comparing the two is that the headphone and master/RCA output levels are quite low on the RB compared to the SB2.

I tested this more thoroughly by trying the same track in Rekordbox set at the same gain and fader levels (and therefore the same master output level at the top right of the Rekordbox window) and the master output knob in the same position on both controllers (3 o'clock). I used the same USB cable and port on my laptop and the same RCA cable, amp input and volume setting on the amp, and the difference is fairly noticeable. I'm not aware of anything else which is set different on the RB which should be resulting in lower output levels.

I also tried a similar comparison of the master output versus my NI Audio 2 DJ in Traktor Pro and the RB was similarly quiet compared to that.

The headphone output on the SB2 seems really good and barely needs to move from the lowest position of around 7 o'clock to be listenable (eg to around 8 o'clock), whereas on the RB no sound is output at all until at least around the 9 o'clock position. The RB needs to be around 2 to 3 'hours' further round for seemingly the same headphone volume as the SB2.

Is this normal? If it is I can live with it and just turn the volumes up, but I'm surprised at the difference given they're both from Pioneer and in the same price bracket. Or should they be the same output-wise?