In the PS Audio Forums Paul McGowan has stated:
Paul CEO PS Audio Sep ’16The BHK preamp has 10dB of gain.
If that is the case, that’s a good thing. You want to be able to have the volume turned up some. 40 (out of 100) is a very reasonable level to set the volume at.
My understanding is that lower gain also means that the tubes will not be run as hard as preamps with higher gain (many have 26 - 29 dB of gain), resulting in less tube noise and longer life for tubes. Maybe someone more knowledgeable can verify or correct that.