CDP vs DAP

I love to write a sentence like these, 100% unintelligible except if you visit audio forums too often.


$6,500		$ 100

You rip a CD on your PC.
Will this sound right, is it possible that a cheap optical drive can equal an high end CD transport?

If you install some software from a CD ROM there are 2 options:
The data is read correctly (bit perfect) or not. In the latter case, the reading aborts.
Small wonder, even 1 bit toppling over violates the integrity of the data.
Today’s optical drives does the reading at great speed making a noise like a turbine, having your laptop shaking and still they read every single bit correct.

If your PC can do this, why shouldn't it be able to do the same with a audio CD?

Ripping a CD is different from playing a CD. When playing, the correct speed is important as the output of the CD transport goes straight to the DAC. Ripping has nothing to do with real time, some rippers can read a track 80 times, just to make sure they read it correctly.

Audio CDs (Red Book audio) is a bit more relaxed standard than CD-ROM.
If a reading error occurs, the error correction comes in to play:

The lowest level is "EFM" or eight-to-fourteen modulation". It takes each byte, and turns it into 14 bits in a fashion wherein it is possible to both correct many misreads as well as tell when a misread is uncorrectable.

Then there is an interleaving, to allow for scratches, holes, pits, etc in the CD data layer.

After that a reed-solomon code is used to error correct and error check again.

After that, if the RSC can't get it right, the player either interpolates (for a block or two) or mutes.

On most CD's there is almost nothing getting past the reed-solomon code. Usually in fact nothing at all

Source: http://www.hydrogenaudio.org/

I think one can safely conclude that modern optical drives are able to read a CD bit perfect.

In order to be sure that we hear jitter effects and not reading errors or interpolations from the CD player we had to monitor the correction flag (cflg) output of the CD-player's decoder chip SAA7376

This was accomplished by an external microcontroller that was programmed to increment the number on a 4 digit display on every interpolation or hold. With this tool we had the accurate count of all uncorrected samples that were output during the track or the entire CD.

The funny thing is, that the low cost CD723 player ($ 99) is able to read any CD or CD-R that is not severely scratched without any interpolation or hold. You can even put it upside down, there will be zero interpolation /hold.

Uncorrected samples could only be generated by dropping the player (5cm) or by extremely scratched CDs.

Source: www.jitter.de

Now if you play the CD from the high end transport and the bit perfect copy on your laptop, will they sound the same?

You play it on the CDP (Compact Disk Player) and you play it on the DAP (Digital Audio Player) and you have both connected to the same DAC (Digital to Analogue Converter), is it possible that they sound different?

To compare them properly, everything should be the same, the only difference should be the two sources.
If you have an integrated CPD (a transport and a DAC in one box) and you connect the DAP to the digital input op the DAC you are not comparing properly.
The transport and the DAC are internally connected using the I2S protocol and this is jitter free by design (both the signal and the timing are provided to the DAC as a word).

The DAP is connected by S/PDIF so the jitter generated by the DAP is processed by the DAC.

If you have a separated DAC and both the CDP and the DAP are connected by S/PDIF then you have a true comparison.

If you do hear differences this can not be due to the audio signal (bit perfect so identical in both cases). The only explanation is the difference in the timing (jitter) or the famous placebo effect.