Is that for all of the pots, or just the ones specifically listed in the wiki?
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The Passinwind Open Source Preamp
- Thread starter Passinwind
- Start date
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
It only really matters for the Bass and Mid pots, or if using reverse log or regular log pots for the Resonance and Frequency controls. I'll have to double check on the latter case, but with linear dual pots things work fine as pictured in the Wiki.
Thanks! When I got back to an actual computer and looked at the wiki I saw that the details for all the frequency pots are on there now even though I only remembered one of them being shown. So now it's a moot point.
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
I just finally finished up a long and arduous contract build, so in the next week or two I plan to revisit the whole Wiki for this preamp. But it's also time to get my butt in gear for NAMM already --sheesh!
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Hi Souvik, I see that we are friends on Facebook now. Yes, by all means use whatever opamps you can readily obtain, and please let us now how that works. You may be able to get a few free samples from Linear Technology if you go to their website, by the way. eBay might also be a workable solution, although the LT chips often seem way overpriced there.
As an aside, I just took a look at the battery in my daily driver Marco Bass with the prototype two band preamp in it. After 7 months of use, unloaded voltage still reads 8.7 volts. These LT chips are very frugal with current consumption, yet they still sound quite good in my designs.
First off all thanx for adding me on facebook sir..and secondly for your valuable informations.
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Time to check back in, I guess. Anybody working on new builds?
I decided to take one of my stompbox versions up to my neighbor's house to jam last night. Ran my active 5-stringer into the front end of his first gen Ampeg BA-115. We were all pretty blown away by how good that sounded. Guess I better keep one around. I'm also just about to order a few new boxes for NAMM builds for this year. These will have amenities added like a stomp switch, LED, and external power supply jack. I'm also leaving enough room for the more upscale Bourns pots this time. I'll share whatever I learn along the way, of course.
I decided to take one of my stompbox versions up to my neighbor's house to jam last night. Ran my active 5-stringer into the front end of his first gen Ampeg BA-115. We were all pretty blown away by how good that sounded. Guess I better keep one around. I'm also just about to order a few new boxes for NAMM builds for this year. These will have amenities added like a stomp switch, LED, and external power supply jack. I'm also leaving enough room for the more upscale Bourns pots this time. I'll share whatever I learn along the way, of course.
I've been playing around with a very similar preamp in pedal form 
Got it from a great friend 
Pretty awesome, I think!
Got it from a great friend Pretty awesome, I think!
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Hey all,
Just a heads-up: Analog Devices recently acquired Linear Technology. For our purposes this means that as of today Mouser can now supply all the components on the BOM, including the LT1351 and LT1352 opamps. I've been playing with a few different other parts in my NAMM 2-band preamp builds that may make it into the BOM for the OS preamp as well, but nothing earth shaking. The LT1351 is currently showing an arrival date of Feb. 12th, so Digikey may still be the best option until then.
Just a heads-up: Analog Devices recently acquired Linear Technology. For our purposes this means that as of today Mouser can now supply all the components on the BOM, including the LT1351 and LT1352 opamps. I've been playing with a few different other parts in my NAMM 2-band preamp builds that may make it into the BOM for the OS preamp as well, but nothing earth shaking. The LT1351 is currently showing an arrival date of Feb. 12th, so Digikey may still be the best option until then.
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- Oct 23, 2005
- 1,439
- 1,378
- Disclosures
- Endorsing Artist: MTD Basses, Bartolini, Genzler Amplification, GHS, Tsunami Cables, Sonic Nuance
The more I ponder this preamp design, using a LP filter with resonance in place of a treble control, the more I like it. I recently just hardwired a couple very very small caps pre-buffer on each of my pickups in an MTD to lower the cutoff and boost a bit at the knee, and this preamp would let someone do this at will and move it around. Great idea.
First of all, I appreciate the generosity shown in the way the project has been shared.
I was curious about the so-called "filter" preamp and a search lead to this thread. It looked like a good place to start experimenting with resonant low pass filters without paying a fortune. Of course, DIY always ends up costing more than you'd expect.
For me, the bass and midrange are redundant but the resonant treble control is fantastic. I don't have a fretless anymore but this section works great for my fretted instruments and lets me dial in definition that I can't get through bass amp eq very easily.
There was an earlier comment about the Wiki being on hold until others have built one. My take on this is since this is a bass forum and not an electronics one the better the build information the more participants there will be. To that end I'm willing to contribute where possible.
I was curious about the so-called "filter" preamp and a search lead to this thread. It looked like a good place to start experimenting with resonant low pass filters without paying a fortune. Of course, DIY always ends up costing more than you'd expect.
For me, the bass and midrange are redundant but the resonant treble control is fantastic. I don't have a fretless anymore but this section works great for my fretted instruments and lets me dial in definition that I can't get through bass amp eq very easily.
There was an earlier comment about the Wiki being on hold until others have built one. My take on this is since this is a bass forum and not an electronics one the better the build information the more participants there will be. To that end I'm willing to contribute where possible.
I'm getting a fair amount of low end roll off with C2 1uF in there:
Simulation is showing that a 4.7uf will get me to 40Hz before it starts rolling off. @Passinwind is there anything I've missed regarding this value? Also, I'm assuming the Excel BOM has the current correct values and not the schematic linked from the first post, right?
Simulation is showing that a 4.7uf will get me to 40Hz before it starts rolling off. @Passinwind is there anything I've missed regarding this value? Also, I'm assuming the Excel BOM has the current correct values and not the schematic linked from the first post, right?
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
The schematic as linked in the WIKI and the BOM match, as far as I can see. Here's an LTspice sim of the rolloff with C2=1uF:
So my model predicts that the low rolloff F3 will actually be at ~16Hz when C2=1uF.
I'm running in severely sleep depleted mode after two intense days of NAMM prep for a luthier friend. I'll try to dig into this a little deeper before I leave for the show, but if I can't manage that I will definitely get back to this thread as soon as I return home early next week. If you are also modeling in LTspice we can take a stab at working through things together then.
And thanks to everyone here who is contributing to moving things along in one way or another.
Completely forgot about NAMM, sorry 'bout that. But I can imagine the kind of shape you'll be in when you return.
My bad, I thought since my schematic had the same file name and version it was the same as the one linked in the first post. It is not.
Don't worry about my build - I will work through it. Thanks again for sharing.
My bad, I thought since my schematic had the same file name and version it was the same as the one linked in the first post. It is not.
Don't worry about my build - I will work through it. Thanks again for sharing.
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Thanks. I did 8 complete onboard preamp installs in new basses in the last two days, and half of those were not even my own preamps.
My model was based on the earlier PW3BLPF_schemo_1_0 that had C2 tied to the half rail:
On the newer schematic it is connected to ground. When I do that I get the same result you did. So that mystery is solved, but not the mystery of why the real thing is acting like the incorrect model. Back when I figure it out...
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Post NAMM update:
This time around I ended up not having time to build up a new version of the OS preamp stomp boxes. We were still doing preamp installs in basses on the Sunday afternoon before show time, and the truck needed to leave on Monday morning. And several of the installs didn't even use my preamps. Good times, or sumthin'. But I'm about to order some enclosures from Pedal Parts Plus and once everything's properly sorted out builders will be welcome to order directly from PPP. I'm thinking of providing a graphics template that you all can customize any old way you want to. That way you could pick your own enclosure and graphics colors, pimp your own names, and so on. Or the graphics can just serve as a drilling guide, which helps a lot in achieving a clean look IME.
The show went quite well for me. There were 4 basses in the booth with my new 2-band preamps in them, three of which were plate-mounted Jazz Bass types. I think that most of those 4 basses were sold at the show, and user feedback was very encouraging. Most likely I will just sign off this design to my luthier friend and he will jump through all the hoops to get it into production. Eventually he plans to sell standalone units if all goes well. I was also approached by another luthier about possibly doing a bespoke version for him, which is exactly how I need and want things to work.
Hopefully it's OK for me to drop this pic here. I was not an official NAMM exhibitor and I did not get paid for providing prototype preamps; this was all just necessary research as far as I'm concerned. And as usual I have no hardware to sell at this time, although occasionally a few close friends have managed to con me into selling leftover prototype builds. So after saying my goodbyes on Sunday I left for my hotel, having timed my departure so I could catch a few tunes on the big main outdoor stage from a band whose bassist is an endorser for Marco Bass Guitars, the guys I've been working with for the last two shows. It was a Portland based band, The Junebugs, and I thought they sounded very good. It turned out that he was playing one of the show basses with my new preamp installed, which no one had bothered to tell me until a few songs in. So much for my canny marketing skills...LOL!
This time around I ended up not having time to build up a new version of the OS preamp stomp boxes. We were still doing preamp installs in basses on the Sunday afternoon before show time, and the truck needed to leave on Monday morning. And several of the installs didn't even use my preamps. Good times, or sumthin'. But I'm about to order some enclosures from Pedal Parts Plus and once everything's properly sorted out builders will be welcome to order directly from PPP. I'm thinking of providing a graphics template that you all can customize any old way you want to. That way you could pick your own enclosure and graphics colors, pimp your own names, and so on. Or the graphics can just serve as a drilling guide, which helps a lot in achieving a clean look IME.
The show went quite well for me. There were 4 basses in the booth with my new 2-band preamps in them, three of which were plate-mounted Jazz Bass types. I think that most of those 4 basses were sold at the show, and user feedback was very encouraging. Most likely I will just sign off this design to my luthier friend and he will jump through all the hoops to get it into production. Eventually he plans to sell standalone units if all goes well. I was also approached by another luthier about possibly doing a bespoke version for him, which is exactly how I need and want things to work.
Hopefully it's OK for me to drop this pic here. I was not an official NAMM exhibitor and I did not get paid for providing prototype preamps; this was all just necessary research as far as I'm concerned. And as usual I have no hardware to sell at this time, although occasionally a few close friends have managed to con me into selling leftover prototype builds. So after saying my goodbyes on Sunday I left for my hotel, having timed my departure so I could catch a few tunes on the big main outdoor stage from a band whose bassist is an endorser for Marco Bass Guitars, the guys I've been working with for the last two shows. It was a Portland based band, The Junebugs, and I thought they sounded very good. It turned out that he was playing one of the show basses with my new preamp installed, which no one had bothered to tell me until a few songs in. So much for my canny marketing skills...LOL!
Last edited:
- Dec 3, 2003
- 23,054
- 45,930
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
I just found this demo clip from the Seattle BassCon, which was all the way back in April of last year. I'd never heard it until last night, and in fact I never knew it existed until I blundered upon it during my cleanup of Facebook Messenger detritus. I'm having some problems seeing it on TB it myself, so let's see if the rest of you are able to view it:
https://images.talkbass.com/data/xengallery_videos/5307/5307892-7e6ee7fd2cb1bad7c2b9de7d746f3a7f.mp4
https://images.talkbass.com/data/xengallery_videos/5307/5307892-7e6ee7fd2cb1bad7c2b9de7d746f3a7f.mp4
