What is purpose of a cd transport?

Why to transport CDs, I guess!

Seriously, I have never really understood why the separate transport route. I think it is a throwback to the latter stages of the LP era in a way where merely spinning the record at a constant speed without introducing noise from the motor was deemed not good enough. The same ill logic is applied to digital where mountains are made of the molehills of spinning the disc. I would think that designing a CD player as one integrated unit makes way more sense than a mix and match approach. So, I really have no objection, except for the cost aspect, to having two boxes instead of one so long as they are from the same manufacturer and made to work with each other.

Since high-end is all about overbuilding and overcharging, the separate transport is a great way of achieving both.

Posters will surely pipe up saying that they always hear great and good differences with separates. In years gone by others would have given objective reasons why the two box solution is better, but these posters have all died mysterious deaths in the last few years...

Like anything else that spins, such as a turntable, how well it works depends on how well it spins. The better transports spin with less vibration and noise, the circuitry and laser are better, and they more accurately read the disc and send the digital data to be turned into analog sound.

Its job is to properly read the disc and transmit the digital data. Some transports use better parts and are better built and are therefore better at doing that than others.

Go listen and judge for yourself.......