Does anyone know how to set this up with the Trimmers?
Cheers
Rob
on the Sam website i find this
“the trimpots are used to fine tune the centre of the attenuverters. So if you find completely attenuated is not exactly central, adjust the trimpots until it is! :). there is 1 trimpot for each attenuverter.”
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I did read that a couple of times but it did not make sense at the time of reading, I think it makes sense now.
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Just curious if anyone has done anything funky with this. Any cool projects to share?
Maybe I’m just missing something, but I went ahead and built this as a dual OBA (with no extra attenuverter or inverted input) on stripboard and everything works except for the boost section. I went ahead and isolated the boost section and tested it again on a breadboard and same thing. Any help would be appreciated if you’re able to see a mistake I made! 
Hi, how do you know it is “not working” ?
The max voltage is 12V so maybe the boost can’t do much anything if the signal is already high.
I built that one and i tested it only with the offset first. Setting it to a low voltage, use the boost to increase the LED signal.
Only thing i can think off as well is that this boost is an inverter so if you have boosted negative signal and only look at the LED (1 or 3) you might miss the fact that it is working.
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Ahhh, thank you - that makes perfect sense!
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My Adaptation of O.B.A. - OBVRT
3.5mm & 4mm (Banana) Inputs and Outputs.
Nifty tool to use for interfacing Ciat-Lonbarde gear with Euro since CL CV signals have a 4.5v DC Offset (Biased at 4.5v/aka Virtual Ground) - this allows for a faux Negative swing on signals below 4.5v DC (2.5v. - 4.5v = faux negative - 4.5v - 6.5v = positive swing) - So having this OBA is a great tool
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I’ve been studying this circuit, nice case study of various ways to use op amps. Also cross-referencing it with the Kassutronics Precision Attenuverter, I got the various parts of working on breadboards, experimented a bit with values, and came up with a different design with two channels and a mixer.
I attempted to build it on a prototype board, but it was a bit too complex and messy for a protoboard and I couldn’t get things to work, so I went and designed a PCB to figure out how to use JLC’s SMD assembly service.
I hoped to confirm with @lookmumnocomputer if it’s cool to proceed further? Like, is it ok to put out a minimum JLC order for my own use? If it works, is it ok to release the file? It’s 80% the original circuit with some values adjusted.
(Also, before anyone points out I could use two TL074: with JLC, it’d be actually more expensive that way!)
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I’d be very pleased if someone who does figure that out were to write up a tutorial on it.
Sometimes two dual op amps are easier to route than one quad, too.
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I’m using this plugin that does 80% of the work! It has a built-in search and outputs the BOM & CPL files in the format JLC expects, takes care of rotations too.
This is from JLC’s own viewer, seems they got it right:
I’ve modified the design a little to use only “basic” parts, the ones they keep loaded on their pick-and-place machines at all times, to avoid manual labor surcharges (it should cost me €28 shipped for 5 PCB, the mimimum order). The plugin lets you search directly in kicad for basic parts, even tells you how much stock they have left.
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Still hooping to hear a word from @lookmumnocomputer! I’ve been sitting on this design just waiting to for an authorization but I’m not sure what are the usual ground rules about re-making mods on your designs
I’m not sure if I should interpret the silence as a “No”? I don’t mind hearing “No” but I hate that I’m just sitting on this Gerber that’s ready to print and waiting on an answer, I sent a reminder DM a little while ago, I’ll just ping @lookmumnocomputer one last time.
I don’t think he would have a problem, it’s not a direct clone , I see you have credited it’s citcuit.
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I hope so, but I’d rather not just assume when I can ask
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its fine! as you know its mainly somewhat datasheet circuits bolted together. go for it!
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sorry, im just crap on computers and going through everything consistently. i must admit its getting worse. i find myself falling into sitting on my computer for ages somewhat procrastinating instead of doing stuff i was supposed to do, so i have been trying to build a habit of putting the computer and my phone in my backpack and leaving them for as long as possible, the downside of this is i come across as bloody rude, very sorry. best means of contact is carrier pigeon.
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not a write up, buuuut
This was how I initially learned -
JLC makes it even easier now - say if they dont have a part - they now have a search option to swap it out for a different component - though, you would hafta update your spreadsheets yourself once you find the replacement.
The only really annoying part through JLC’s service is finding all the LCSC numbers on their parts library.
Some companies offer to source all the parts based on your spreadsheet and position files.
But it really is as simple as generating 2 files for them, and sourcing the parts in their library
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Thank you!
The order is sent, we’ll see next month if it works, I’ll share the Gerbers if it does! First SMD order for me.
I took the opportunity for a last minute design change (if things go wrong, there’s enough test points to hack in something). And to add a little doodle by a friend of mine.
I don’t have the patience for a 30mn video, but scrolling through it quickly, it looks like most of the stuff he’s doing is fully automated by the plugin I suggested! I certainly didn’t have to bother writing spreadhseets manually.
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