I have both of these pickups and while I've never mixed the two, I think this would work well because they each bring out different characterstics of a bass. I used to mix the Realist with an Underwood and that was a good combination; the Underwood added some string sounds and midrange punch that the dark and woody Realist was missing. I would imagine the Realist/Bass Max combo would offer the same versatility.
BTW I ultimately decided to use the Realist by itself, keeping the Bass Max as a backup. I hated the extra gear and knob twiddling that was required to mix the two pickups and I'm still happy with the sound I get in most situations.
- Steve
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