there is really clever and crazy guy who is into noise cancellations, DACs, LPS, etc...
He started an discussion on github so check it out
https://github.com/rootscript/audio-dumpI am into a process of finding good LPS for little money. If you going to buy from China supplier always check they have wire all in under regulations!
Very often you going to find that the casing is made of aluminium or other metals but there is no earth conductor wired in! Also make sure you got one with fuse on DC side! As the last thing you want in case of fault to blown you pricey equipment plugged into it
Regarding the transformers used in LPS for DACs and other audio gear, the R shaped seems to be the best choice as the produce less noise than EI or worst doughnut shape toroidal
R-core
EI shape
doughnut shape
I am in needs of more than one as I have multiple RPis at home. One which is in my another RPi 3 for my , than Raspbian based media server, and RPi in
So I would go for unit like this here
They seems to use good selection of components, you can customize output voltages, even colour of the unit.
I know few people who buying from this seller and they saying the quality is very good for such money.