Again, this is 100% about amplitude. You have limited controls in that you can record at 0db on the mic preamp or -10db. Such is the limitation of these “all-in-one” solutions. Since you can only control the mic preamp by a factor of 10db at a time you need more control. You can achieve that with that amp and either leave the mic preamp at 0db and turn your amp down, or you can put it at -10db and turn your amp up (presumably in both cases). If it’s too loud for your apartment environment than no amount of gear or gear tweaking with the equipment at hand will change that.- Using the -10dB setting on the mic? I tried that with the mic a mere few inches from the amp and the whole recording was quieter than the iPad's built-in mic, even. I can try that again and maybe turn the amp up a little to try to compensate, but I'm then in danger of just being too loud for the apartment.
EDIT: Regarding the iPad’s built-in mic. For loud sound sources the iPad has a built-in limiter that reduces the dynamic range. As I mentioned previously, louder is really just a less accurate way of saying less dynamic range. It is not surprising at all that the iPad’s mic would be louder on a source that was clipping a large diaphragm condenser USB mic.