How simple can an audio computer be?

Will be able to compare USB, optical and coaxial from a single device.

The HifiBerry steel case provides good durable protection to the Pi and HAT and adds weight which helps it stay put.  I use them and like them, they allow WiFi and Bluetooth to be used. They necessarily have perforations for connections and ventilation and the 2 parts are not positively electrically connected, so (at computer operating frequencies) it's not a Faraday cage, but better than an EMI transparent plastic case.

Containing EMI requires carefully designed enclosures, you may remember the hoops that Graham jumped through in developing the Accession case to satisfactorily achieve EMI shielding.

With the high frequencies involved in modern digital devices, physical separation is your best friend.

Ian

Thanks for the info. Yes if the Optical has the "Acoustic Mass" of the Coax definitely it would have been the super star. However I just wonder if a better optical cable can make any Difference. 

I plan to clean the optical cable tips with the optics cleaner we use in our work place.

Example: https://sg.rs-online.com/web/p/fibre-optic-cleaning/1038582/

In my work application it definitely increases the intensity of light through the optics, not sure of the Audio quality improvement. 

What is your opinion on your CD Transport? This is the Belt Driven model right? How different it is from the Conventional Direct drive Transport?

   The belt drive supposedly has the advantage of moving to motor further away from the laser, thus reducing reading errors caused by vibration. Unless I had the same machine with a conventional set up, I’d have no way of knowing of how much of a difference it makes. It’s REALLY quiet mechanically compared to other CD players I’ve had, and I’m extremely happy with the sound. 

My only complaint is the price. Talking Australian dollars, the recommended retail here is $4,400, but in Japan it sells for $1,200 Australian dollars. So I bought mine direct from Japan. I think it’s around £2,200 in the UK.

Mick.