Currently available LDO's are immensely noisy and not applicable to Audio designs. I design own LDO's by the formula Voltage reference ( such as LM431 ) -> heavy filter at the output -> heavy, RC filter after and in series to the output -> buffer -> heavy, RC filter -> output amplifier -> power transistor ( s ). Optical isolator can be inserted in this chain, too. Whether the optical isolator rejects or introduces noise is questionable, but, this is not the question. The question is whether an audio quality, IC, which, requires, just, resistors, capacitors and output transistors is good and whether AD should make such. Attached is the idea.

 

You do realize that capacitors larger than a few pF can’t be integrated?

 

You do realise that Texas Instruments makes low-noise LDO regulators?
https://www.ti.com/lit/ds/symlink/t...764&ref_url=https%3A%2F%2Fwww.google.co.uk%2F

 

How much noise is "too much", in your application?? Then, for audio work, how precise does that regulation need to be??
Certainly a regulator voltage drop reduces efficiency, but usually for low level circuits the small amount of power waste is not an issue. For higher power output stages I have not seen amplifiers with regulated voltage, as usually, providing an adequate power transformer and a large enough filter capacity provides the ability to meet most audiophile requirements.

A very useful means of reducing all power supply noise is the addition of a filter inductor to the filter string, instead of only resistors. Aside from increased space requirements and a greater cost, a filter choke would be a simple solution in a " no-compromise" design.

 

LDO's are immensely noisy

Some people are using "LDO" to indicate any linear regulator. LDO stands for Low Drop Out regulator, which is a class of linear regulator. LDO will work where the input and out voltages are close together. Many linear regulators need 2 to 3 volts (input to output) to work well. A LDO needs about 0.5V. Some much less.

I agree that LDOs are not the best at regulation because they were designed for low drop out not regulation.
Linear regulators are pretty good. Most have an internal reference built on the TL431.

I would use a TL431 or a brother of it with a RC filter or a RCRC filter.
I think your noise comes from the front end of the op-amp.
I would not use a R-R input op-amp for audio.

There is a ref+ two op-amp IC and a ref+ op-amp + comparator IC. I would not use them for audio.
TI has a good line of "audio" op-amps.