Bumping this old thread because it was so helpful!
I, like many others, oscillate between emotions about my A4. While it does certain things very well it always feels like a lot of work to get good basses, especially across octaves; you might create a tight mid bass that falls apart in the lower ranges or a good deep bass that relies on extreme filtering thereby losing its top end sizzle.
While most A4 users likely know about using the multimode filter with keytracking to boost low frequencies, there were a few other takeawys from this thread that I found very useful.
1.) The filters are the main source of bass woes; as evinced by oscilloscope images of external gear being run through the A4. In order to get the filters to behave in an “expected” manner (similar to other synths) try the following: for filter 1 take off res boost, leave keytracking off, set res to around 64, and leave the cutoff all the way open. I found that a bit of overdrive is also useful with positive values of 12-25. Use the multimode filter for your filtering needs (envelopes, LFOs etc.).
2.) It is possible to get a pretty hefty square using the tips in step 1 and by setting PW to ranges between -2 to -8.
3.) Not from this thread but it is also possible to get a nice saw by following step 1 and setting the oscillator shape to triangle. Next, turn the PW to -64 and voila.
While there are some other tips here and there, working around the above three (with tweaks to taste) has been incredibly helpful and I have achieved some bass sounds that I thought were outside of the A4’s palette. Of course there is no accounting for taste so experimentation is key but I am now back on the positive slope in my A4 relationship.