I believe you can contact the distributor, Divergent Technology, and they can increase the gain. I can't remember by how much or the charge to do this.
Modifications to improve gain of ASL mini phono.
I use Mullard 12AX7 on my mini phono and it improves the bass a little. I use Shure V15 type V cartridge and my Sonic Frontiers SFL-2 preamp volume is at 12 O'clock level. I wonder if there are mods to improve gain on the mini phono.