on the market regulators

SuperTeddyReg

perfect. For us so far the best regulator available for "DIY" projects. Can be ordered directly from Teddy Pardo. We like to use a +5V unit for the analog stage of the DAC.

LT1963EQ

midrange price, ultra-low noise <40μV adjustable voltage regulator module, 1.5 A, we liked it for a budget project (main supply for everything, connected to pi's +5V pin)

LM317

cheap (depending on the components), variable output voltage, vivid, a legend, with excellent PRAT

TPS7A4700

good data sheet ... ultra-low noise, expensive, the DIYINHK unit can easily be integrated, just needs a transformer and you are ready, it offers +5V or +3V3, sound wise not convincing, definitely not for that price tag

AMS1117

extremely cheap, fixed output voltage, available with +5V and +3V3 output voltage, not a great sound

Naim Discrete Regulator

unfortunately something like this is not available. Let us know if you have one for us. We would like to try it.