This no-name power supply brand on Amazon gave me a significant improvement amazon.com/gp/product/B08HDGCP3V.
I was prepared to get no improvement. Wanted to convert my Pi power supply from 220v to 110v, took a punt on the low price to see if it would make any difference over the standard Pi wall wart. Was surprised by a substantial improvement along the lines you would reasonably expect with adding a better power supply to decent hi-fi components.
See my full comment on this thread: Raspberry pi 4b ultra low noise Power Supply - #15 by Sven_Eschholz
Presumably all down to a reduction in noise in the audio signal.
Apologies for taking the OP’s thread off course!