Hej Amy, the FMB is not related to soundcard specifics such as gain etc. – neither Soundjack is some kind of amplifier. However, if you talk about your own (loopback) signal have you made sure to increase the (large) volume fader on the SJ settings (on the left) to the very right (maximum) ? It is set to 20% in its origina state. That being said you need to adjust gain at the soundcard level.