The Passinwind Open Source Preamp

Discussion in 'Pickups & Electronics [BG]' started by Passinwind, Dec 25, 2016.


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  1. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I'm finally starting to gear up in earnest for SMD work. I have a microscope and new lighting incoming, and plans to turn over some old school bench gear for more relevant pieces.

    In the meantime I've started working on some boards that are probably at least "DIY possible" for quite a few people. For me hand soldering 1206 parts is no big deal at this point, especially if I take a little break after doing the more demanding bits before I dive into the rest. I reckon I could build up a board like this new three bander in about an hour or so without much stress these days:
    PW21B.JPG

    That's a test bed for a more tunable bass section, and also the second build I've done with the OPA2145. Both aspects show a lot of promise and are likely to make it into the next OS 3-band boards, I think.
     
    Last edited: Feb 17, 2021
  2. BassikLee

    BassikLee Commercial User

    Feb 13, 2004
    Deltona, FL
    Owner: Brevard Sound Systems
    Have you tried air soldering? At the very least, it's fun
     
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  3. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yep, but unfortunately I've not yet managed steady access to the tooling.
     
  4. I'd be willing to take a crack at that, but I'd need one of those air de-soldering suction pumps — just in case.
     
  5. SteveCS

    SteveCS

    Nov 19, 2014
    Hampshire, UK
    It is difficult to measure as it is quite a convoluted shape, so I tried trace the outline and add a few key dimensions. There isn't much space in the top route, especially where it narrows down at the far end. This is looking from the top, so output is to the left and volume to the right...
    20210218_064756.jpg
    ...and it is only 1.25" deep...
    20210212_193748.jpg
     
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  6. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Random update:

    The OPA2145 has turned out to be an absolute champ so far in various builds I've tried it in. It compresses less when pushed hard than many FET opamps I've tried and scoped, and headroom is exceptionally good. It's also been quiet and very stable, and availability has been no problem thus far...yay!

    Digikey are now offering a similar small quantity board production service to OSHpark. The MOQ is four boards and that costs $6 per square inch (for 4 boards), shipping included. Beyond that, you can just bump up the quantity in single unit increments, unlike OSH who only go by threes, so if you need say five or eight they can do that. The boards are red, of US production, and have the same ENIG finish for the pads as the OSHpark ones. Minimum size is 1 x 1 inches, so OSH is still the best US option for really small stuff. I'm going to order a set for a new two band build spec today, with the quoted turnaround time at ~10 days.

    The standalone LPF filter board is nearly at the top of my build queue now, finally. I have all the parts on hand and it should go very quickly. I've also caught wind of a new commercial filter preamp builder in the UK and hope to have a few beta test samples in hand within the next month or so. I only have a few details but I like what I'm hearing from the builder so far. Can't really say more myself just yet, but if you sniff aorund BassChat you might find some details soon I think.
     
    Last edited: Apr 1, 2021
  7. Chip shortage is a problem for sure. I have a few 2145s in my cart, which I created more than a year ago now, but at no point has everything been in stock. A recent concerted effort to replace backordered parts with comparable substitutes (ex: different voltage/temp range/tolerance part -- invariably more expensive) has me down to a single backordered item with no suitable substitute. It should be back in stock within a few weeks, but what are the odds something else isn't out of stock by then!
     
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  8. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yep, I've had to resort to downgraded voltage specs, different pad spacings, etc. just to keep things rolling. And my last Mouser order took over a week to ship, but at least that matched their posted disclaimer.
     
  9. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    And for once it did:

    PW23B.png


    Actual size is 2.07 by 0.88 inches (52.6 x 22.4 mm). With SMD resistors in 1206 format it would be ~1.66 by 0.88 inches. I could also get height down to ~7mm with some different electrolytic caps, this version is right around 9mm.
     
  10. -Asdfgh-

    -Asdfgh-

    Apr 13, 2010
    UK
    I'm hoping to find my soldering iron again this weekend, after moving. First port of call is a series of fixes of pickups, and then work on a piezo pickup for one of those short scale, six string piccolo bass things. Then I might start looking at the preamp. My wife is away so I have time, but sadly she's also vastly better at soldering!
     
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  11. Looks great, Passinwind!
     
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  12. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Just a heads up on a potential new commercial design that I caught wind of on Basschat: Experimental Prototype bass... I hope

    I expect to get a couple of test boards in soon and will post a dedicated thread on it eventually if it comes to fruition. I have no affiliation with the maker, but he solicited my feedback and as always I'm happy to give that when it makes sense.
     
  13. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Thanks, here's the latest "what-if" format I came up with a couple of days ago:

    PW23B_smd.JPG
     
  14. You gotta name these things something like: Gnat, Midge, No-Seeum... I've seen postage stamps that were bigger. :laugh:



    I've been collecting some smaller SMD project boards to practice on. A buffer, a 1590A reverb, and a couple others. I figure, "Sure, I'll practice soldering SMD, but I still want something useful resulting from the effort". I don't get the SMD "practice" boards I've seen... you could maybe use them as a coaster, or lightweight paperweight.


    If [when] my micro-buffer and A'Verb etc work out, I'll be hitting your Oshpark page hard.
     
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  15. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Cool. It gets easier, that last build I pictured took right around an hour and 1206 resistors would've gone just as quickly for me by now. But something was not quite right with that boy, so I built another one the next day which unfortunately manifested the same misbehavior. I've shelved them for now, but will work it out sometime next week. It's a good excuse to finally break out the microscope that @AudioTaper set me up with recently, if nothing else. ;)
     
  16. A9X

    A9X

    Dec 27, 2003
    Australia
    Wery interesting build PW. Aesthetically the UK build is more than a little challenging for me, but the design of his pickups is very similar to what we're prototyping now. Pre is similar in general topology and opamps ( mine summate individually, not series and are SC, 5st in the proto). If I've read it right he doesn't understand he difference between 2nd and 4th order.
    My psu is almost identical to yours but 5 pin XLR. Proto pre is a current hog.
     
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  17. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    He hasn’t sent me the info on the volume/mixer board yet, not sure how it’ll ultimately be configured. I haven’t done a deep dive through the whole thread yet, but the whole thing looks like a definite work in progress. Nice guy though, and I always enjoy talking with fellow travelers, so to speak.
     
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  18. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Shipping to my PO box turned into a bit of a snafu but the service rep tells me they've now sorted things out permanently and he got back to me very quickly at least. I ordered and paid for 4 boards but actually received six, and they look quite decent:

    DK_Board.png

    Digikey requires a full set of Gerber files rather than a single .brd file, and unfortunately they're not set up for board shares just yet. But I'm expecting that they'll have a fully integrated modeling data/layout footprint/BOM/parts ordering/board fabrication, and maybe assembly workflow all in one place sooner than later, which would be uber cool.
     
  19. BassikLee

    BassikLee Commercial User

    Feb 13, 2004
    Deltona, FL
    Owner: Brevard Sound Systems
    That looks great!
     
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  20. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Yep, I'll report back once I get one built up. I just ordered a set of new three banders to see if they have their shipping act together now. I'm optimistic, my interactions with the DigiKey support staff have always gone pretty well.
     
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  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Sep 24, 2021

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