So when I record guitar or bass, I put a SM57 and MD 421 on the amp, basically center cone. Then a large diaphragm condenser about 3-4 feet out in front of the amp, and finally the DI track in case I need to re-amp: 3 mics/4 tracks per guitar or bass. Maybe overkill but it sounds GOOD. I've never had to re-amp anything and the DI track is GREAT for seeing the transients, since amp tracks are usually undefined blobs of waveform.
I still have my gear set up from when I tracked my Mexican Player P-Bass with stock passive pickup. I have the DI track going into a channel on my FMR Really Nice Preamp. The gain knob is at 48db and the thing only goes to 66db so, yeah, you'll have to turn up the gain. That's about 3/4 of the way up the dial on this knob. If your bass is anything like my basses, there will be notes on certain strings that are super loud compared to others. Just make sure you're not breaking the meter on the preamp into the audio interface.
I have a UAD system and use Distressors on the three microphone tracks and each is set at 6:1 and to hit pretty fast. I now know why people love Distressors on bass. But the point I'm trying to make is the signal won't be amazing at first. But you compress it more than you would think, maybe hit it with some tape saturation or a saturation plugin and perhaps using EQ ahead of all that, and you'll make it sound fine.
This is the DI track of just the P-Bass into a Radial DI into the RNP into the Apollo x16:
View attachment P Bass DI Track (no effects).mp3
And then the three microphone tracks, mixed together to a bus and the Decapitator with maybe 1-2 db of the meter working:
View attachment P Bass microphone trackes mixed.mp3
I left the mic-mixed tracks at the levels I have them in my project, which is the two close mics' faders at about -2/-3 db and the room mic somewhere at like -6/-8db (they're a lot quieter than that in the meters, it's just the fader levels). They still ended up close in volume to the 0db fader'ed DI track and for sure more even in volume. I attribute the evenness to multiple mics on an amp plus compression.
Edited to add: I use flatwound strings because I play guitar and I like to keep the skin on my fingers. I picked this bassline but usually I finger pick because it is so fun! The amp is a Hartke TX600 into a Seismic cabinet I bought on sale on Amazon and put a 12-inch 400-Watt Yamaha bass speaker into that I bought from a local guitar/music shop
Double edit: Ha, I misspelled 'tracks' on the one file. d'oh