Music Reference RM-4 and Sumiko Blue Point 2

I've just got Pro-Ject RM5 SE turntable with Sumiko Blue Point 2 cartridge. I've connected the turntable's output to Music Reference RM-4 phono preamp input. And then to headphone solid state amplifier. The system is playing, but the sound level is very quite, barely audible. Apparently the output signal that is coming out of Music Reference RM-4 output is really low.
On a back panel of Music Reference RM-4 there is a printed note saying there are some input/output "switches" located inside the box to control the output gain and something else... I have opened the box and inspected it inside. Unfortunately I couldn't find any "switches" there.
I have been using THIS phono-preamp (Music Reference RM-4) in past with my another turntable (Oracle) with Orthofon SPU Royal N. And it worked just great. I think the reason must be in difference that exists between Sumiko Blue Point 2 and Orthofon SPU Royal N voltage output. And I probably should set properly those "hard to find" switches that are inside Music Reference RM-4. Here is the basic characteristics of Sumiko Blue Point 2:

Cartridge Type: MC
Output Voltage/Channel 2.5 mV
Load Impedance 47k Ohms

Many thanks in advance!