# Passinwind Open Source Hybrid Filter Preamp Builds



## Passinwind (Jun 9, 2022)

Backstory here: https://www.talkbass.com/wiki/pw3b-lpf-open-source-onboard-preamp/

The Wiki could use some love, it's been a few years since I've done anything with it. There have been a few false starts with new versions and most of what I'm going to post here are various new iterations that only myself and a few beta testers have built up. The long Talkbass thread has a zillion swerves in it, but at least two or three commercial makers have spun off their own onboard preamps using some of the information there to get a leg up. But far more people have built pedal versions for themselves, and I'd love to spin off a more feature rich design fork here. These things already work especially well with amplified acoustic guitar and mandolin and that direction is probably going to be my primary focus for a while. But, open source...you tell me! 

So, throw the onboard preamp in a test box and print a label on the home inkjet:






That box has served as a demo unit for several years and I actually just took it back as a trade in from the mandolin player who hosts a cool weekly jam I play half a mile from here.

Put one in a $$$ bass for NAMM 2017, but it was a last minute half ass install (by the luthier) and the bass itself was a bit duff unfortunately. The same year we brought along two in pedals with enclosures from Pedal Parts Plus:





But the booth slaves never really figured out how to drive them and although one online bass oriented magazine did a YouTube feature on it I was still the only one contributing much to improvements. The lack of available dual gang reverse log taper pots suitable for back routed basses was an ongoing hassle, and the linear ones we were all using gave a fairly limited useful frequency sweep range. But eventually I discovered that Omeg would happily make as few as ten units for easy money in a month's time. Great, I ordered a dozen and they work exactly as expected. While they were being built I noticed that Tayda had started stocking some cheap Alpha ones, so for pedals it was now game on, finally. So grabbed a free Adobe Illustrator demo and came up with a quick and dirty trial box from Tayda:





Meh, I can certainly do better, but for whatever reason my next go with a newer AI trial version just didn't quite work out. Tayda really needs to offer digital proofs before printing, IMNSHO. And there's no reason at all to push AI as the exclusive solution for UV print file generation, although I've run into this with much more uptown outfits as well. But I'll cop to not doing a good enough job, and Tayda is obviously doing a whole lot of things right. So I'm just sending one of the "not quite right" mandolin beta test boxes out to my brother for testing during his busy gig season this week, calling it B stock:





I do think that wood knobs on the copper hammertone finish are kind of a cool look, and these walnut ones came to me as unfinished test units for an Etsy vendor called Pick Knobs, who are a joy to work with. He loves doing custom work and the sky is pretty much the limit for inlays, weird shapes, and so on.

And then on this very forum I saw some posts about Amplifyfun, who are about an hour's drive from me and seemed perfect for my particular wants and needs. They'll accept various file formats, give great feedback along with the digital proofs, cost essentially the same as Tayda, and for me economy shipping takes one of two days to arrive. And if I use LMS for enclosures that only takes a day to get to Amplifyfun since they're both in Portland. These two were my trial runs over the last few weeks, using Gorva S90s with the premium sparkle finishes:










The bottom one is the color shifting "chameleon" finish, which goes purple under the right lighting conditions. Pics don't really do justice, it's killer.

OK, enough for chapter one of this book!


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## Bricksnbeatles (Jun 9, 2022)

Looks nice! I’ll have to breadboard it to see if it gets a spot on my acoustic board


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## Passinwind (Jun 9, 2022)

Bricksnbeatles said:


> Looks nice! I’ll have to breadboard it to see if it gets a spot on my acoustic board


That'd be cool, I actually never bothered to do it on a breadboard, just LTspice straight to OSHpark. The newer versions have an extra buffer/gain stage in front of the LPF section, I'll be happy to share a schematic via PM. It's not really necessary in this case but I was spinning off a standalone LPF board for per-pickup resonant LPFs a la Alembic and Wal where you'd definitely want it. You'll probably want to raise the input shunt resistor value a bit too if you are using it as the front end in your signal chain.


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## Passinwind (Aug 4, 2022)

Next gen boards for these are stuffed and ready for wiring:





I'm going to take a stab at using a higher supply voltage this time around, mainly because I have a nice 15V line lump supply looking for a job. I think I'll be using this enclosure, but I have three other options on hand at the moment too:


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## Passinwind (Aug 15, 2022)

Almost done, should be making noise this afternoon:


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## Passinwind (Aug 27, 2022)

And this time, with some sub opamp parts to see if I can get through the parts supply issues for another month or three:


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## Passinwind (Sep 18, 2022)

OK, let's add another function and fit see if we can fit it all in a Gorva C-65:






Meanwhile, here's the latest Gen2 build, which I've already posted in a couple of other threads here:


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## MichaelW (Sep 19, 2022)

@Passinwind are you selling these boards? I'd love to build one of these.


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## Passinwind (Sep 19, 2022)

MichaelW said:


> @Passinwind are you selling these boards? I'd love to build one of these.



Sure. The original through hole version is available on a board share at OSHpark, follow the link in the first post. The new two board hybrid SMD version is in beta testing with a few builders right now, PM me and we can talk about that. And then I've been talking to a certain, ahem, well known DIY PCB vendor about doing an all in one pedal centric version, which I think is pretty likely to happen.


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## MichaelW (Sep 19, 2022)

Passinwind said:


> Sure. The original through hole version is available on a board share at OSHpark, follow the link in the first post. The new two board hybrid SMD version is in beta testing with a few builders right now, PM me and we can talk about that. And then I've been talking to a certain, ahem, well known DIY PCB vendor about doing an all in one pedal centric version, which I think is pretty likely to happen.


Awesome! I just ordered the board(s) from OshPark. I have a buddy that's been bugging me to build him a preamp for his acoustic rig.
Also, since I'm now a "bass owner" (notice I didn't say "bass player" hahah) I think I need one of these babies!


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## Passinwind (Sep 19, 2022)

MichaelW said:


> Awesome! I just ordered the board(s) from OshPark. I have a buddy that's been bugging me to build him a preamp for his acoustic rig.
> Also, since I'm now a "bass owner" (notice I didn't say "bass player" hahah) I think I need one of these babies!


Please PM me your email address and I'll get you some info on mods for your purposes. I'll be putting that in the Talkbass Wiki soon as well, just waiting on feedback from someone I sent a modded board to a couple of weeks ago. One big change is that inexpensive dual reverse taper pots are now readily available from Tayda, so dropping $$$ on the linear Bourns ones we were using 5+ years ago is not the way to go. And the specified low current Linear Technology opamps are way overpriced and not the best choice for pedals anyway.


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## MichaelW (Sep 19, 2022)

Passinwind said:


> Sure. The original through hole version is available on a board share at OSHpark, follow the link in the first post. The new two board hybrid SMD version is in beta testing with a few builders right now, PM me and we can talk about that. And then I've been talking to a certain, ahem, well known DIY PCB vendor about doing an all in one pedal centric version, which I think is pretty likely to happen.


Does said DIY vendor have forum identity issues and needs to shave his avatar?


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## MichaelW (Sep 19, 2022)

Passinwind said:


> Please PM me your email address and I'll get you some info on mods for your purposes. I'll be putting that in the Talkbass Wiki soon as well, just waiting on feedback from someone I sent a modded board to a couple of weeks ago. One big change is that inexpensive dual reverse taper pots are now readily available from Tayda, so dropping $$$ on the linear Bourns ones we were using 5+ years ago is not the way to go. And the specified low current Linear Technology opamps are way overpriced and not the best choice for pedals anyway.


Done! Thank you!!


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## Passinwind (Sep 19, 2022)

MichaelW said:


> Does said DIY vendor have forum identity issues and needs to shave his avatar?


I know nothinnnk...


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## Passinwind (Oct 6, 2022)

Passinwind said:


> OK, let's add another function and fit see if we can fit it all in a Gorva C-65:
> 
> View attachment 32552



Yep, it all fits:






Ready to go live with shares for two of the three boards for this, and the new HPF boards are due in tomorrow, so that one shouldn't be far behind.


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## Passinwind (Oct 17, 2022)

Heh, up to v4 on the HPF boards and still not sure which one is the winner. SO-8 opamps are starting to come back into stock everywhere and I'm currently working through six different flavors in various combinations...this could take a while!


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## Passinwind (Oct 22, 2022)

v2 of the WTHPF, done and tested:





The new opamp lineup I tried this time may or may not really be any better in this application, but they're definitely not worse or a lot more expensive and there are currently plenty in stock, so all good.


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## Passinwind (Jan 5, 2023)

Coming soon, WTHPF v3:





Trying some Cusack 1590BBS enclosures this time around, the Gorva C-65 was a bit of a PITA to fit everything into and naturally I wanted to add another feature or two. Planning to implement a DI out next.


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## cwsquared (Jan 5, 2023)

Passinwind said:


> Coming soon, WTHPF v3:
> 
> View attachment 39625
> 
> Trying some Cusack 1590BBS enclosures this time around, the Gorva C-65 was a bit of a PITA to fit everything into and naturally I wanted to add another feature or two. Planning to implement a DI out next.


And I just got my V2 set yesterday...


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## Passinwind (Jan 5, 2023)

cwsquared said:


> And I just got my V2 set yesterday...


Cool, the new one uses those same boards too. So you can add either or both other modules if and when you feel like it. I already have HPFs built into all my bass amps anyway and don’t necessarily need the variable gain stage, but those features are very important to two actual paying customers, hence the bigger enclosure. Plus, I really don’t like to do the exact same thing twice!


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## cwsquared (Jan 5, 2023)

Passinwind said:


> Cool, the new one uses those same boards too. So you can add either or both other modules if and when you feel like it. I already have HPFs built into all my bass amps anyway and don’t necessarily need the variable gain stage, but those features are very important to two actual paying customers, hence the bigger enclosure. Plus, I really don’t like to do the exact same thing twice!


I like modularity, especially in this case.


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