You're trying to solve something backwards:
- Need low noise voltage supply
- I know that I can reduce noise using a large capacitor
- Therefore, I need a large capacitor
- Therefore, I need a capacitance multiplier to give me a low-noise supply.
3 (and, in some ways, 4) are logical fallacies.
What you need is a low noise voltage regulator. The idea that this would be realized with a capacitance multiplier is from the 1950s to 1960s, when no good voltage regulators existed, but people were getting used to transistors and later opamps and were excited about the possibilities¹!
A large capacitor, either a real one ore one simulated through a capacitance multiplier, is just that: a kind of energy storage, a cap. It can help smooth out things, but it's just a smoother, not actually a regulator.
You have all the energy you need to keep things smooth (on the input side of your regulator), so you can do better than just having a large capacitor.
If you look into the data sheets of modern linear regulators, even low-drop regulators (LDOs), you'll find that they can achieve awesome things like Power-Supply Noise Rejections (PSNR) of > 60 dB. No way you can do that with a capacitor, and especially not with one controlled by a less-than-complex feed-forward "regulator":
Seriously, all the transistors involved are ancient, and the results will be nothing but a voltage that's worse regulated than one supplied by a sufficiently designed actual voltage regulator based on higher-speed, lower forward drop semiconductors. 1.5 A output current really isn't that much. Use something less ancient than the LM338, and a fraction of the actual capacitors used here, and you'll get better regulation.
more current handling capacity from the capacitance multiplier circuit by paralleling output devices?
- either that capacitance multiplier works well in emulating a low-ESR large capacitor, then: probably not, because you might end up building an oscillator, could be solved by adding dampening, but that would counteract the purpose.
- or that capacitance multiplier has a high output impedance, in which case it'd help, but that would just prove that the idea of using this capacitance multiplier is a bad one.
¹ The fact that this is from an audiophile forum does reinforce that presumption, as they tend to glorify the "sound of old-timey tech".