I use the AX8 as my DI box for all my acoustic needs. That includes steel string, nylon string, and even banjo. Not only does this avoid having to run another XLR cable and use a DI box, but it makes it easy to create presets for each instrument and tweak the sound to optimize each. Check out this tutorial for tone matching your acoustic instruments to a mic'd sound on the AX8 -
(Hey Smitterfar, is that your vid? If so thanks!). Creating your own tone match is going to sound way better than trying to use a match someone else created with a different instrument and pickup system. And the ability to create presets with EQ, IR's, and effects makes the AX8 orders of magnitude better than using even the most high end DI box.
As far as feed back control, here are few strategies I've used:
- Use the PEQ block on your preset to kill problematic frequencies
- Get one of those feedback buster sound hole plugs
- Some of the newer mixers (like the Soundcraft Ui24r) have build in automatic feedback suppression that does a surprisingly good job.