Reference Transports: An overall perspective

Germanboxers,

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So, you are saying that mis-reading a "0" for a "1" or vice-versa with some random frequency will cause the sound to become like a blender? It won't just misrepresent the amplitude value of the complex wave at those particular sampling points? Assuming a .1% error rate, that's still 40 some errors in amplitude resolution/sec.
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It is due to the way PCM is encoded. Once again do not think of this as an analog signal. For CDs you have data which is 16 bits long. If any of the LSBs (least Significant Bits) were transfered in error, then you would probably not notice this. But as you mentioned since this is random, any of the 16 bits could be transfered in error. If any of the bits which did not reside among the lesser significant bits were corrupted the amplitude error would be huge. Yes, it would actually sound worse than a blender. Just think of what happens if one iota of a note went from very soft to very loud almost instantaneously.

Fortunately, this never happens for a properly designed player. Because there should be ZERO errors after error correction. Like I said, if your transport is failing, you will know it. It is not subtle.

Bombaywalla, ALL CD/DVD/SACD players have a sled with linear tracking for the Laser, except for the famous Philips "swing arm" transport which is now obsolete. The big VRDS-NEO and some newer Philips transports are using a combination between radial and linear tracking where the focusing lens is "suspended" on magnetic field. Since this type of “suspension” is inertia-free, it is the fastest and most accurate reading technique available.

You CAN NOT prevent the disc from wobble, especially with higher than x1 rotation speeds when SDRAM buffering is used, without having a FULL disk support on the top (or bottom in the case of Pioneer "Stable Platter" system). With the Audio Desk Systeme Lathe you're talking about, you can balance the disc and prevent from vibrations caused by eccentricity, but NOT wobbling.

From what I know, the Esoteric VRDS you have in your Wadia spins at x1. The VRDS-NEO spins at about x10 using a large SDRAM buffer from which the data is clocked out. This allows the Laser to go back 10 times and re-read the data should there is error sensed by the DSP. Also, the VRDS-NEO is the ONLY transport currently available which is NOT suspended in any way. Still, even at this very high rotation speed, there is NO vibration you can sense. The READ error rate of the VRDS-NEO is almost 0 (if not 0) but Esoteric still uses the latest Digital Signal Processing with the most powerful error correction AND memory buffering in order to make sure that the error and jitter are indeed ZERO. There is no other disc spinning device (including CD/DVD-ROM) to offer these qualities.

Also, even though with computer based audio certain "error free" software can be used, this does not exactly mean that there are no transport device READ errors.

Any current $150 universal player uses powerful DSP and memory buffering which according to your and Lktanx theory is sufficient to do the job providing error and jitter free data output. Why don't you get one of these and hook it up to an external DAC together with your x1 reading and non-memory buffering VRDS Wadia and see which one will sound better? I can tell you right now; your Wadia will be a LOT better. Also, when you were talking about your friend’s computer based audio with external DAC did you try your Wadia as a digital transport through the same external DAC? If you have not, please do that and let us know if the computer based “error free” “transport” can provide the same bass extension and the same top octaves clarity, air, openness and resolution as your Wadia will.

In conclusion, it is a real fun for me to read all these "error free" discussions, but at the end of the day, there are many other VERY important things when it comes to digital audio other than "Zero" error.

Regards,
Alex

"Also, even though with computer based audio certain "error free" software can be used, this does not exactly mean that there are no transport device READ errors."

Alex, if one uses (and correctly sets up) Exact Audio Copy (EAC) along with a good CD-ROM drive that supports both C1 and C2 error correction (a Plextor Premium or similar) then you *will* get bit perfect copies, as long as there is nothing inherently wrong with the disk. If there is, EAC will give you an indication each and every time an error is detected. Any scenario which would cause a read error that was not detected by this set up (I'm not really sure that's possible) would neither be detected by a dedicated transport.

Having said all that, I agree with you completely that a bit perfect audio image is only part of the picture. But the tradeoffs between a server based bit perfect image and a fine transport are smaller than the D/A conversion of either of these signals, IMO. I've just recently moved to a server based world (a Squeezebox into my D/A converter), and guess what? That does not sound quite as good as my transport (a Proceed PDT3) into the same converter. Is it comparable to some of the other transports I've tried over the years? Yes. Is it scary close to what I have now? I'm afraid to say, yes, with the deficiency being (I believe) in the Squeezebox, and not in the server based delivery of a bit perfect signal.

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Any current $150 universal player uses powerful DSP and memory buffering which according to your and Lktanx theory is sufficient to do the job providing error and jitter free data output. Why don't you get one of these and hook it up to an external DAC together with your x1 reading and non-memory buffering VRDS Wadia and see which one will sound better? I can tell you right now; your Wadia will be a LOT better. Also, when you were talking about your friend’s computer based audio with external DAC did you try your Wadia as a digital transport through the same external DAC? If you have not, please do that and let us know if the computer based “error free” “transport” can provide the same bass extension and the same top octaves clarity, air, openness and resolution as your Wadia will.
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Alex,

I am only discussing transports and their associated error correction circuitry. Let's not compare different issues. Of course a Wadia will sound different than a PC playing a CD. This difference is not and should not be due to the transport and error correction. This is because both the Wadia and the PC possess transports/error correction circuitry which produce ZERO errors.

The Wadia sounds different because it has a different clock reference with different jitter characteristics. The Wadia also has different digital filters and DAC. So obviously they should sound different. Nevertheless, I will not state which sounds better.

I am not claiming that all CD players sound alike. I am claiming that a properly designed CD player's sound should be completely uncorrelated with the transport. The sound will be a function of the following (not in any order of importance):

1. Digital filters
2. DAC
3. Clock reference
4. Clean analog power supply
5. Output driver stage of DAC

Note, the transport/error correction circuit is one thing engineers can do perfectly, inexpensively, repeatably, and in large quantities.

I am purely speculating on the actual numbers but here is an example:

High end transport = 1 error per minute
Cheapo transport = 100 errors per minute

Obviously the high end trasnport is better here. Now with error correction:

High end trasnport with EC = 0 errors per minute
Cheapo transport with EC = 0 errors per minute

I hope this helps you decide where to invest your hard earned $.

Tonyptony and Lktanx, every CD player, even the cheapest one, has C1 and C2 CIRC error correctors which have certain ability to "correct" the error. If the error exceeds the capacity of the C1 and C2 THEN you have an Error Flag output. So, if there is no error flag, this does not meant that there is no error; it means that C1 and C2 were able to correct the errors. Also, please be aware that there are also error correction errors which mean that C1 and C2 sometimes will "correct" something that did not need to be corrected. The other VERY important factor is the EFM Jitter, for example, if two different CD drives have the same error correction engines which will ALWAYS report Error free output, the one that has less EFM jitter will sound better.

In the case of my example in my previous post I meant not using the Wadia as a stand alone unit, but A-B testing it against the computer based "transport" through the same EXTERNAL DAC. In this case, digital filters, DACs and Analog stages will not be the cause of the difference.

My point was also that even a $150 universal digital player uses VERY powerful error correction and memory buffering using large 64Mb (and some times 128M and 256M) memory chips which completely "remove" error and jitter from the reader similar to what can be done with a computer based digital. So my question to you is why then those error and jitter "Free" digital players will not sound as good compared to even a 15 years old regular CD player when used as a digital TRANSPORT ONLY. I am not talking about stand alone use.

This is what I meant when I said that there are many other important things other than a fake "error free" digital data output.

Given the CD surface is really perfect, with the Esoteric VRDS-NEO transport the error is REALLY Zero, not only that, but the EFM signal jitter is also MUCH lower than anything else currently available.

I am sure that one day soon you will realize that “error free” and “bit perfect copy” doesn’t really mean anything when it comes to digital audio sound quality.

Regards,
Alex