Frank,
When it comes to top-quality, there are only several CD transport manufacturers in the world of which Sony, Philips and Pioneer are used the most for building audiophile equipment. There are some manufacturers building their own mechanisms, but the Digital Signal Processors (DSPs) used are still Sony, Philips or Pioneer (and strangely enough, some recent Sony and Denon products use Panasonic). This being said, I have extensive in-depth experience with all of the above that includes pure CD, CD/SACD and CD/SACD/DVD transports.
You are correct that it is much easier to obtain best results with a regular CD transport, but there are limitations to it. The processors are old, noisy and 16 bit (no headroom). The disc spins at x1 speed so there is not much room for large size memory buffering (only 512KB of FIFO memory is used), and the so called "read until right" is impossible, so you hit it and it skips.
On the other hand, most CD/SACD/DVD universal transports are built with newer, faster and quieter DSPs with at least 24 bit resolution (lots of headroom for CD data processing). The DSPs have built-in memory controllers and large SDRAM memory devices attached to them (16, 32 or even 64MB). The disc spins at x4 filling up the SDRAM memory. The laser pick-up can go back to a problematic passage and re-read it until the best information is retrieved, all while you are enjoying uninterrupted audio data coming from the memory buffer. The transport jitter is greatly reduced. But what is the problem with such transport then? Unlike CD-only transport, the “universal beast” needs multiple clocks produced by a PLL-based multi-clock generator, usually locked to a 27MHz video clock reference. The PLLs used are very jittery thus decreasing the entire transport performance. But what if the original PLLs and VCOs are replaced with a single PLL solution that is so advanced that its phase noise is as low as the one of a bare crystal? You have a winner, and there is no regular CD transport capable of competing with it, IMHO!
Best,
Alex Peychev
