I'm afraid that thread is a bit over my head.
Don't bother. They claim impressive figures but they won't get it stable, at least not without throwing much more money and elbow grease at it. Playing in the the 1ppm and better league isn't something you mange to do by just sketching a few parts. I did a few example calculations, but the chose to ignore it.
So, I'm am looking for a dac.
You need three things, a good reference source, the DAC and a gain stage.
- Good reference, because otherwise any change in the voltage reference will be seen on the LM317 output. But not an ultra pricise reference, because the LM317 adds its own error.
- DAC, not more than 12 or at maximum 16 bit, since this is still manageable for beginners, e.g. to get stable, low drifting. And because there is no point in going higher because of the specs of the LM317.
- The gain stage because of the way the LM317 needs to be driven. You need to generate Vout - 1.25 V with the DAC. And these days there aren't many DAC that can produce, let's say 15V output directly. When you find one you should expect to have to add a reference voltage as high as the maximum output voltage. If you go for an external gain stage instead you can use a DAC with a relatively low build-in reference (resulting in a relative low maximum DAC output voltage) and compensate for this with more gain.
So, I would recommend a quality DAC with build-in reference, to minimize the hassle. I.e. pay a little bit more for less hassle. Followed by an OpAmp as gain stage, probably configured as an adder, so you can get below 0V, which in turn means you can take the LM317 below 1.25V to 0 V output.
Have a look a Linear's LTC1257, LTC1451, LTC1655 or similar. In case you want to control other things or more LM317th, have a look of some of their dual or quad DACs.
[Linear also has DACs with higher output voltage ranges, and their soft span DACS are fun, but I don't think they fit your problem well]