Last I checked, a DAC's Vref should come from a seperate source.
I think you're trying to steady the supply voltages for the whole circuit, if I read you correctly. The diagram seems to have the 317 dictating output voltages which feeds Vsupply for all the other chips.
Last I checked, all these components work within a certain voltage range, i.e. 4.5 to 5.5 v. So you'd be looking to eliminate the transients. You can do that simply by adding caps right at the Vsupply and GND pins of each IC. An oscilloscope would give you a detailed picture. A standard PSU would have transients in the 1kHz to 10 kHz range (from the switching), and might have some around 60 Hz (from AC).
Does that help?
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