Hi All I eventualy found the exact article at https://www.digikey.de/ so if your in germany or on the continent this is a reasonable source. Costed 18.00 Euros to ship and 1.46 Euros per LM4040. I got a couple of other parts to make it worth while. And they delivered it fast so it was kind of worth the 18 euros.
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Pain getting these again…
£1.41 at Farnell but there’s £9.95+ handling charge before and VAT to total £15.42 for two!
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I used LM 4040 AIM3-4.1 from Reichelt: LM 4040 AIM3-4.1: Shunt voltage reference, fixed, 4.096 V, ± 0.1%, SOT-23-3 at reichelt elektronik
They are in a SMD package and I just soldered two legs onto it and hot glued everything in place.
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Did someone try with a LM 4040 CIZ-5,0 from Reichelt ? Is it work ?
Did you use the TL431 for a Kosmo 1222 build? I’m having a hard time sourcing the LM4040 and I’ve got some TL431s, but the pinouts look really different. How did you wire it up?
I made my own PCB for the VCO, it’s basically the same as the 1222, but worse as I did not put the pots in the right place and such stuff… But yeah, I used a TL431 instead of the LM4040. I don’t know if it’s better or worse. The VCO is okay, but I have issues with the tracking with the octave switch, but back at the time I did not know that I should have matched the resistors there… I can try how it tracks with just CV input though and tell you, but then again: no idea if it’s because of the TL431…
If you can source a LM4040 5.1, I would try that first… otherwise you would probably need a tiny extra stripboard for the TL431 
My circuit for the reference voltage looks like this:
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Ahhh, gotcha. Thanks for the swift reply!
In case it helps in sourcing, as noted above, you can presumably use a BIZ, CIZ, or DIZ with no problems, or a 5.0 instead of a 4.1. The A/B/C/D designations correspond to different tolerances, but since you’re just using it to feed a trimmer, really whether it’s 4.096 V or 4.156 V or even 5.0 V doesn’t matter, you’ll just set the trimmer differently to get 4.00 V out.
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