Gain spec of Joule preamps in product lit are not accurate. I have actually measured many different Joule preamps.... in default shunt to ground volume control configuration, a Joule LA-150 has little bit more than unity (i.e a few tenth more than 0db IIRC) gain at max volume. Switching the preamp volume control jumpers to voltage divider got you around 6dB.
CheersRich
CheersRich