So from the AHB2 manual, three input gain settings:
Low-Gain = 22 dBu (9.8 Vrms)
Mid-Gain = 14.2 dBu (4 Vrms)
High-Gain = 8.2 dBu (2 Vrms)
From the D90SE manual, two output voltage settings (XLR):
4.2 Vrms @0dBFS (4V mode setting)
5.2 Vrms @0dBFS (5V mode setting)
From my naive...