Anti-jitter RAM buffer in DACs, Which have one ? Options

[Pio2001]

In, http://www.tc.umn.edu/~erick205/Papers/pap...html#principles we can read about RAM buffers :

This process is referred to as timebase correction and as stated before, any quality piece of equipment will implement it.

That has been the ritual answer to jitter concerns since I'm on the Internet.

But... if "any quality piece of equipment will implement it", then some non-quality pieces of equipment don't implement it. My question is : which ones ?

The statement "quality piece of equipment" is completely subjective and doesn't give any information. For my grandfather, a "quality" CD reader will be a portable radio-cassette-CD-speakers combo for 100 $ in the supermarket. The "non-quality" one will be the Fisher-Price toy for children from 3 to 7.
For an audiophile friend, the "quality" CD player will be the 25,000 $ Wadia CD Transport+DAC, while any player under 1,500 $ is just worthless crap.

So, do a 200 $ CD Player always have a RAM buffer ? Or is it not considered a quality piece of equipment ? What about a 300 $ CD Player from 1990 ?

[Patsoe]

You're pointing out the exact reason why a two box transport/DAC combo has jitter problems: you can't afford buffer underruns, since even the most unmusical listener will hear that.
So, when an spdif link is used, DACs don't use their own free running clock; instead, they have a clock that can follow the transport's clock. This is an ugly process: the perfect square wave that the transport's clock may well have is lost in the long way to the DAC; there's non-ideal cabling, noise, intermodulation between data and clock signals, and lots more. The DAC then, is not following a perfect clock at all!
So you see, 'in real life', buffer over/underruns are not a big problem. But precluding those problems causes this other problem.

As to one box cd-players: the rate at which their transport reads is controlled by the same clock signal as the DA-rate. By principle, the fifo will always be filled then. The purpose of a fifo here, isn't in the first place to buffer reading speed variations, but to cope with the fact that bits don't all have the exact same length on the CD surface.