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The signal and bass and mid caps are pretty much all on 5 mm pin spacing, so quite a few other brands and types will most likely fit and work OK. I'd recommend at least sticking with the suggested 2.5% caps for C6 and C7 and 1% resistors for the frequency and resonance bits though: R11, R12, R13, R14, and R15. We definitely don't want this thing to turn into an oscillator, which it would be perfectly happy to do with a little "encouragement."
I thought you liked weird, Charlie!
Can you make it a way huge ringworm emulator?
I think you and Marco could make this happen. Just sayin'.
Disclaimer: For a while I've been wanting to put one or another of my DIY onboard preamp designs into an open source DIY oriented format that other TB'ers can build and readily tweak to their particular wants and needs. I've finally settled on a specific concept and am well into testing a few different versions. I'm about to send out a build kit to my first beta tester, and I will also have a few builds mounted in stompboxes and a bass or two at NAMM in a few weeks. I'm hoping to have v1.0 wrapped up a few weeks after the show, at which point I will release a board share at OSHpark.com, where anyone can order up three boards at a time at OSHpark's usual DIY-friendly rates. I'll have zero financial stake in that, and likewise for the BOMs for Mouser and Digikey that I will also provide. All of this has already been vetted by the TB Admins, and I recently ported my status to Commercial User in anticipation of eventually licensing this or some other of my designs to one or more OEMs. I think that puts everything up front, but please just ask if anything seems shady in any way. This is new territory for me and I want everything to be fun for all involved.
Intro: OK, so what about the pie, already? The design features pretty standard bass and midrange control circuits, with a treble section using a swept frequency, variable resonance low pass filter. Here's a graphical representation of various treble control sweeps modeled in LTspice:
And here's a look at the Resonance control function, with Frequency set at the lowest setting:
These are just sample filter alignments and overall gain settings, there is a fair bit of adjustability available with a few component value tweaks.
Here's the first gen circuit board, which has already been superseded by a new one of the same size, which is roughly 2.2" x 1.67":
Current cost from OSHpark shows three boards at $18.30, shipping to nearly anywhere included. Things like board sharing or group buys on pots or other parts will be up to whatever community evolves from this thread. Open Source means that any or all of you are free to do your own perfboard or PCB layouts, mods, ruthless criticism, and so on -- as long as you share all that stuff here. I'll be happy to provide tech support until a mature build spec is reached, and hopefully we can then have a TB Wiki featuring collective wisdom on best building practices, wins and losses with specific pickups and instruments, sound samples, and of course build pics.
As far as overall cost, I anticipate that $50-100 will cover most build specs. Shipping from at least two or three parts sources will likely suck up a fair amount of that at first, but hopefully we can eventually figure out a way to mitigate that some.
I've gone out of my way to use simple "cookbook" type public domain circuits and to avoid using hard to source parts like reverse audio taper dual pots. I have spec'ed fairly expensive and somewhat obscure opamps, but many cheaper and more common subs will probably also work pretty well. If that proves to be true then paring the BOM down to a single source list will be a lot more feasible.
There you have it, my Christmas present to TB, the PW3B-LPF. If any of you are not familiar with Creative Commons licensing, here's a link to the specific license. View attachment 1020173
The license link will always give access to the current schematic version. Please use that link and do not post the schematic in this thread, since TB will cache it and it will inevitably become outdated.
The TB Wiki for this project starts here.
