Gain Problems with Zoom R 16 and GarageBand

[gvdv]

Hi,
I have reverted to using my Zoom R 16 as an audio interface (USB) with GarageBand after having had problems for years with my Presonus Firestudio (really loved the preamps on the Presonus, though), and I have a couple of questions related to this.

Unfortunately, I cannot get enough quite enough gain on the GB tracks, despite cranking the R 16's trim knob and boosting GB's track gain, and am wondering if anyone has any ideas about this - today I thought about putting some kind of effect on the track in GB in order to enhance the signal, but will not be able to test this idea for a few days.

Will this work, or are there any other ways in which people can think of either boosting the R 16's gain further, or enhancing the signal within GarageBand?

Thanks,