Help! My preamp/DAC is unable to drive my poweramp

My Bricasti M12 is unable to drive my Nagra 300p amp. Even at max volume of +8dB, the loudness in the room barely reaches 85dB.
Would love some advice from the audio gurus before I give up on my Bricasti M12.

My speakers are Devore O96 which can be easily driven by 8W SET amps, leave alone a 20W Push pull amp like Nagra 300p.

It has something to do with gain of the preamp. Impedance matching seems to be fine.

Bricasti m12 preamp/DAC specs:

Balanced Analog Outputs Connectors: XLR balanced (pin 2 hot) Impedance: 40 ohm Output: @ full scale ( +8db front panel )+16.5 dbm (5.2V RMS) D/A Conversion: PCM 24 bit delta sigma 8x oversampling, DSD direct 1 bit Frequency Response @44.1k: 10 hz- 20 kHz +0dB, -.2 dB Dynamic Range: >120dB A-Weighted THD+N @ 1k: .0008% @ 0dBfs / .0004% @-30dbfs
Unbalanced Analog Outputs Connectors: RCA Impedance: 40 ohm Output level: Full scale ( +8db front panel ) = +10.7 dbm (2.6 V RMS) D/A Conversion: PCM 24 bit delta sigma 8x oversampling, DSD direct 1 bit Frequency Response @ 44.1k: 10 hz- 20 kHz -.2 dB Dynamic Range: >120dB A-Weighted THD+N @ 1k: .0008% @ 0dbfs / .0004% @-30dbfs

Nagra 300P specs:

2 x 20 watts RMS stereo into 4, 8 and 16 Ω
14 Hz at 56 kHz, +0/-3 dB
> 70 dB
Typically 105 dB (ASA-A weighted)
0.8% @ 20 W
> 48 kΩ
«Soft start» circuit
Incorrect mains voltage (115V or 230V) Output transformer removed
Error in tube anode current <15mA or >180mA 120 W continuous, <1 W stand-by
100, 115, 230 V ± 10%, 50-60 Hz