Since the Afterburner's bridge spacing is a tad narrower than 19mm, the stock spacing on the Fat Stacks worked out perfectly. Well, I assume these have stock spacing, but they were custom ordered to have the pole "twist" reversed for fanned fret application, so it is possible that the spacing was changed as well. I didn't order them - bought 'em from DavidRavenMoon after a fanned fret project of his got postponed.
The basic difference - Fat Stacks are less sizzly on the high end than the stock FD3's. I like darker sounding pickups because, for whatever reason, my playing technique seems to really bring out the treble response of a bass. Some players just seem to have "bassy" hands, some have "trebly" hands, and I'm definitely in the latter group.
The FD3's are good, but for me, they're just not the ticket. I'd turn down the treble to tame them a bit, but then I'd lose the presence I like. I like my bass to sound like it's right there, I like it to have immediacy, and with the treble backed off on the FD3's it started getting a bit of a "playing through a blanket" feel to the sound, a little distant. Hard to describe. I tried an Aguilar OBP-3 and the Audere with the FD3's -and of course, the stock passive system - before deciding to try some different pickups.
The Fat Stacks, as I said, are more muted on the high end but still have great note definition and character. Clear, clear, clear, all the way up and all the way down to low B. Response seems pretty even, but I can't really judge yet 'cause I need to deepen the routes in the Dingwall a little - the stock routes are rather shallow compared to most basses. An extra 1/4" of depth will give plenty of height adjustment. Right now the pickups are bottomed out and it's fine on the bass side, but the treble side needs to come down a bit (my preference due to my trebly hands).
Loads of flexibility here with the coil switching. Single coil mode gets nice and raw and right up in your face, humbucker mellows things out a bit but remains very present. And things get really interesting when you mix things up - single coil neck with humbucker bridge, series, parallel...... and the Audere pre has a buffered blend, so blending pickups is completely smooth. 70% neck/30% bridge? 40/60? No problem - it's all there.
