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Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it.

I think I'm finally starting to understand what you are proposing ...

*** I know one buffer that will surely do, the buffer sized 800M,
but then you have to hit the stop button on the DAC. ;) ***

So what you are essentially proposing is a "DAC" that:
- buffers an entire CD into memory (800MB)
- then plays back the whole CD from memory under control of a local clock
- with transport controls (Play, Pause Stop) embedded in the unit to control the buffer playback

If that is what you are proposing, then I agree, such a unit (i think it should be more appropriately called a player rather than a DAC) should exhibit very low jitter.

I think you will find people like Ted would also agree with you - I suspect Ted was assuming you were proposing a mechanism to reduce jitter in an outboard DAC with SPDIF as the only input method.

Of course, although you have avoided data interface jitter, you still need to be careful of other factors that may still induce other forms of jitter. For example, memory access latencies can cause jitter (Stereophile reviews of some of the early hard disk players reveal they have jitter as bad or worse than CD players). You also need to consider shielding the DAC from EMI generated by the microprocessor. And you also need to watch out for the microprocessor inserting noise into the power supply which then increases intrinsic jitter.

But assuming you have solved all those problems, then yes, you should have low jitter.

In fact, you don't need to buffer the entire CD at all. What you can do is have a relatively small buffer, but read the CD in non-real time (ie. using Digital Audio Extraction) and fill the buffer on a "just in time" basis. That's the approach I am using in my player.


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