o.k anybody know anything about shm-cd they claim there indistinguishable from the master?

One of the ’advantages’ of digital is you can make copies of the master without any sonic loss. So the big sonic differences that existed between various vinyl pressings from different countries is mostly a thing of the past. So if the sonic quality of the master is any good, all cd pressings made from that master will probably sound good as well.

The one remaining variable is the manufacturing process of the disc itself. In my experience Japanese cd pressings usually sound a little better, even if they use the same digital master as its source. I suspect this can be attributed to better manufacturing, as Japanese cd’s are much better centered than cd’s manufactured elsewhere. It seems the laser/transport has more difficulty reading discs which are not centered, causing errors that need to be corrected in the digital domain. This manipulation may affect sound quality.

SHM is only about the material of the disc, not about manufacturing or digital processing (like Victor’s K2 or XRCD mastering). The SHM cd’s do feel somewhat heavier than regular discs, but it seems a stretch to attribute any sonic benefits to this.

So the data is encoded as a series of on and off, or ones and zeros. This is the digital system, it's an encoded language. The actually transfer and storage of the data exists in the analogue world. A  flip flop is an electrical circuit, used to store a value, this is what the digital data is stored in with RAM.

The quality of the storage system/device and the retrieval of the data is all done in the analogue world. For example it could be via a cable, where the electrical signal energizes and de-energizes delivering the pattern representing the values of the data being conveyed. The device creating the analogue signal, electrically, through an oscillating stream of light, or a radio signal, what have you, the connecting medium through which the signal travels and the end device that through engineering has to read or discern what the signal represents have varying degrees of efficiency.

The encoding is called digital, as for the entire rest of the computing system including the transfer of the language it's electronics and can be transferred by light pulses or an electrical system, radio signals. All of these methods of transfer of a language are prone to mechanical limitations and failure.

Digital being the organized structure of the data may be perfect, the storage, retrieval and conversion from and back to the analogue world is not perfect. That is why the technology for storage, retrieval, computation and conversion is always being improved upon by engineering methods.

As for SHM CD this appears useful >

https://www.cdjapan.co.jp/feature/shmcd_allabout

They are like any other CD recording there are some good ones and not so good

What is a  SHM CD?