Passinwind

Thanks! I have no interest in selling production hardware at this time, especially in rack enclosures that typically cost a fortune these days. I do however love sharing open source designs with DIY'ers though, for instance: https://github.com/Passinwind/PW3B-LPF I did have a website up for several years offering design services, but The Plague put an end to that dream and I just use it to archive info on my DIY stuff these days.

I recently did a new DIY preamp for my Marco Bass MV4: Bass/Midrange EQ for the neck pickup, resonant LPF ("filter") EQ for the neck one, active mixing, detented volume pots with gain cut and boost available for each pickup. Stereo output possible but not currently implemented. I was recently given a second body for this bass, the new one has a bit of fire damage from the luthier's shop fire a few years ago but appears to be salvageable.

I've owned Ashly BP-41 and Alembic F2B ones, both of which were very cool within their lanes but not quite my long term cuppa. As usual, I'd rather just roll my own: That one is sitting over a commercial 1000 watt plate amp with DSP processing in the pic, but the power amp is now gone along with a more Fender/Alembic style rack job I did: And then I've done a few tube ones: ...which uses 6SL7 and 6SN7 tubes. The second version was two rack spaces rather than three, like so: And then my favorite is in a half rack width format, meant to fit side by side with either a tube one or a DIY 700 watt amp: And then the very similar preamp in this integrated 500 watt amp build can be run completely independently of the power amp section: I still own the first one and the last two, a luthier friend now has #2 and #3 and has taken both to his NAMM booth, and #4 belongs to a well known pro who primarily uses it in his home studio.

Just confirms what we all thought, really. Dude With Tudes 'R Us.

More knobs = more tone. Or not, depending, but I have less than zero use for any passive basses in what passes for my world.

Modulate keys by circle of 4ths/5ths. Whole songs, not fragments. Interpose lyrics between songs, ignore the changes and do it all to one groove. All of those approaches worked well in the one band I fronted for many years, but my stated goal for audiences was sit down and shut up, not dance monkeys.

Here's my Marco Bass MV4 fretless, which is now on its third DIY preamp: This time around I did a "filter" preamp for the bridge pickup, and a more standard Bass/Mids job for the neck pickup. Then the pickups are mixed to mono actively, for the moment at least. Easy enough to do a Ric style stereo breakout though, as the four conductor cabling has a spare available. I set it up so the neck volume control mutes everything, but turning down the bridge pickup fully still lets the neck one come through at a slightly diminished level. The volume pots are detented with more or less unity gain at the noon positions. That allows makeup gain when big cuts are used, leveling out big tone control boosts, and up to a whopping +24dB of gain at bass full up, pretty much still dead clean. There's "Q switch" for the filter resonance, currently with two gain options but probably with a third one added whenever buying the right switch is convenient. I play with a slide quite a bit and solo on many many songs, this new format makes grabbing a brighter more cutting sound trivially easy and although this bass has always sounded quite nice this is by far my favorite iteration.

For a digital possibility, you might want to take a look at the MiniDSP stuff, for starters. No programming needed, just a simple WYSIWYG interface and nothing to build yourself in many cases. I've never looked at chaining two of my open source HPF boards to make a 6th order filter, but it might be feasible. If I needed that transfer function I'd probably just do a new layout though. Fixed frequency certainly makes things much easier in any case!

Always happy to share starter files for fellow travelers breaking into the LTspice world, just PM me if you might find that helpful. I typically use a bit different 2nd order/ 2nd order format from fdeck et al, mine doesn't need a multisection pot and is meant to interact with the bass control in some pretty specific ways. There are lots of workable ways to skin felis catus though! For steeper alignments like 36dB/oct I've just used digital solutions, FWIW.

IMO LTspice is a much better tool for the job, FWIW. You can even run .wav or .mp3 files through your model and have a listen, if desired.

Look at the old fEARful (sic) threads on Talkbass. Those threads are a bit messed up by now due to board software changes but the plans are still readily available with a bit of looking around. If you go this route you'll want the "True Three Way" crossover variant, which some TB'ers developed outside of the original designer Dave Green's purview. He did approve it somewhat reluctantly though. I've done a few more uptown 15/6/1 versions of my own design too, but never really documented them that thoroughly.

Dang, hoping for you that it was the other one.

Through the power amp output or the headphone one?

I repaired amps professionally for many years and there's no chance I'd try to repair a high power Class D module for component level faults without extensive documentation and access to factory tech support/blessing for advice and parts. The modules are generally "replace, not repair" parts, and with good reason as they are quite complex, dangerous, and rigorously regulated for radio frequency noise emissions, especially here in the US. Does Thomann offer repair service on these? That seems like by far your best chance of getting it working. Please be very careful, 300+ VDC is not uncommon in these things.

Probably about a 1% chance, or less. Do you have a proper schematic, signal generator, dummy load, etc?