AIR

[Hermanh]

It is said that linear power supply is very effective for improving sound quality of PC/Mac based transport. I am wondering whether linear power supply is effective for AIR. Does sound quality improve if PC/Mac is supplied with linear power supply? Has anyone tried this?

I think with recent Macs the power supply is built in. The Mac mini a few generations ago had a separate power supply so a linear supply could be substituted. People who tried this had varying opinions, some finding a vast improvement some no difference so I think you will have to try it for yourself in -your- system.
I use 2 Metric Halo ADC/DACs which come with off-board switched mode power supplies. A few years ago there was a big internet debate about this since lots of audiophiles use these for the DAC section alone, which is SOTA.
I tried it at the time myself and could hear no difference, Barry Diament who uses them for his recordings at Soundkeeper, felt that the linear power supply he tried was actually slightly worse in the bass.

It probably does come down to try it yourself at home, in the end, since the internet experiences vary so widely.
My theory has always been that a competently engineered component should be immune to the sort of interference which -may- be generated by SMPS but there are plenty of cottage industry products in this hobby which may have some compelling feature in one sense whilst not being thoroughly engineered in the traditional way. If you have one of these it may be susceptible.

My experience has been that some of my kit is improved by mains filters and some not affected at all, which is part of the data leading to my current opinion.

In my Windows based system I installed a separate PSU (battery) for my SSD and a separate PSU (Teddy Pardo) for the USB-Card both of which greatly improved sound quality. I gained more detail, a blacker background and an improved soundstage.