Reference Transports: An overall perspective

Germanboxers, I would like to emphasize that you are right; the transport is very important. It is responsible for getting the data correct. However, getting the data correct is very easy and very inexpensive and very trivial. All PCs today rely heavily on CD/DVD transports doing their job well. In a PC, when a transport fails, you throw it in the trash and get a new one.

Lktanx, you do understand that a digital bitstream is just a voltage (analog) approximation of a series of square waves representing the "1" and "0"'s? It's not just mathematics.

I was not referring to massive errors resulting in skips, etc. What I was referring to was the fact that all physical systems exibit some degree of random variation (random error for sampling systems) and these non-correlated errors cannot be "corrected". The question that neither of us can answer conclusively is to what degree does a transport that exhibits less random errors have on the final sound quality?

Ram buffering makes a great deal of sense...on that we agree completely!! Why do you suppose a company like Esoteric has gone through the trouble and expense of developing an incredibly massive and robust transport (VRDS Neo) for exclusive use in players that also SRAM buffer the data? I certainly wouldn't offer this as "proof", but it is interesting that over half the cost in their machines is taken up by the transport mechanism...and all of them read the data to SRAM. It would be interesting to be able to take two of their machines, pull the VRDS Neo out of one, stick a CD-ROM transport in it, and compare the sound side by side.

Anyway, interesting discussion. As an engineer, I'm somewhat baffled at times by what can make apparently meaningful changes in the sound I hear. I'm equally baffled by some of the absolute crazy stuff being peddled by some as well.

Germanboxers,

Yes, the 1's and 0's are represented with voltages. But unlike an analog system where any slight deviation is considered distortion, the digital system is orders of magnitude more impervious to signal variation. Here is an example.

Consider a typical system where 0V represent a "0" and 3V represent a "1". For a "1" to be mistaken as a "0" the 3V will have to drop below 1.5V. In the analog circuit case any variation is bad but for the digital case the signal has to lose half it's value before a mistake is made.

Another way to think about this is that in an analog amplifier, the designers have to make sure that distortion is below say 0.1%. But for a digital system, you can tolerate up to 50% signal change (i.e. 3V dropping to 1.5V) before one error is made. Furthermore if an error is made, the use of error correction fixes this issue.

I can say for certain that the data read from a transport after error correction will be ZERO (unless you're thumping the player with a hammer). If this is not the case you have a defective unit and you should get it replaced. Furthermore, if your defective unit is producing bit errors, you will definately hear it. It will not sound like "the soundstage of the music has narrowed". It will sound someone turned on the juice blender for a brief period.

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.

Again, I don't offer this as conclusive proof, but why would a company such as Esoteric spend mucho $ on developing and manufacturing a massively overbuilt (by an order of magnitude in weight alone) transport when the machines they are placing them in also buffer the data to SRAM? I don't think it's reasonable to attribute this decision to marketing bs...way too expensive without meaninful return for that.

Jordan

Jordan/Germanboxers,

it appears that you have not spent much time in thinking about the CD transport stuff. When you write your posts, you seem to be writing ex-tempo & there does not seem to be much depth. you are also blowing the importance of the transport -w-a-y- out of proportion, if I may say so. Transports are very important but they are a means to an end. The end being to get the data read reliably & as quickly as possible. Spend some time & research the matter.

Lktanx has understood the subject matter exactly!

>> The question that neither of us can answer conclusively
>> is to what degree does a transport that exhibits less
>> random errors have on the final sound quality?
I can't remember exactly when this was (maybe it was in grad school) but I remember spinning a CD that had holes drilled in it. NOT THROUGH HOLES; rather, holes drilled deep enough where they encroached into the recording material. These holes were made in the N-S-E-W directions so it looked like an equal-legged cross. Also, the holes were NOT made in the TOC area just so that the CD player would actually play the CD. The objective of this was to demonstrate to us the robustness of the error correction. So, obviously the disk had to play! There was an exact 2nd copy of this disk that was pristine (like the one you'd get from a store). How did it sound? For all practical purposes it sounded just like the pristine copy.
So, what does this tell us? If there are certain # of errors while reading a disk, the error correction system can neutralize them & the sound of the reproduced music will be practically unchanged to the user listening. If the # of errors increases to the point that it overloads the error correction system, then, the sound will be degraded & will "It will sound someone turned on the juice blender for a brief period".
The CD error correction has an enormous appetite for errors & it takes a significant # of errors to break it. Randon errors are just that - random! They do NOT occur at a high enough rate to overload the disk error correction algorithms. Just as Lktanx wrote, if you have a unit that does create a high rate of random errors, you have a defective unit & the transport needs to be repaired/replaced.

>> Again, I don't offer this as conclusive proof, but why
>> would a company such as Esoteric spend mucho $ on
>> developing and manufacturing a massively overbuilt (by
>> an order of magnitude in weight alone) transport when
>> the machines they are placing them in also buffer the
>> data to SRAM?
there are many aspects in the design of a transport. what distinguishes a good one from an average one is: (1) the disk clamping system. A CD spins at 200-560RPM (most of the time, I've read 360RPM). The edges of CDs are not perfectly smooth or straight. Hence, at that speed, if the CD is clamped only in the middle, the CD will wobble. In effect it becomes akin to reading a newspaper placed on your lap in a subway train! In the transport there are surges in electrical current drawn from the digital supply by the laser optics electronics. This has the effect of dirtying the digital power supply & this crud pollutes everything it touches. Also, as the disk wobbles, the laser beam becomes unfocused. An unfocused beam can make errors reading data. So, TEAC's VRDS system was designed to clamp the ENTIRE disk. Does this come for free? NO! it adds weight to the whole transport but it is 1 possible solution to preventing the disk from wobbling. a 2nd solution is available too - a CD cutter w/ a fine edged knife. I believe that it cuts 200 CDs before the blade needs replacing. Solves the same issue by having the user spend less money than buying a TEAC VRDS system. (2) the laser system in an average CD transport has to tilt or rotate so that it can read the entire CD surface. This has the bad habit of spreading the laser beam. this is said to increase jitter & also possibly cause read errors. So, what TEAC does in its VRDS & VRDS NEO systems it that it has the laser pickup on a sled. This pickup operates just like a linear-tracking tonearm on a TT. However, this sled has to be stable. Does this come for free? NO! it adds additional mass to the transport. Plus, it needs a motor & a clean power supply, which add further weight to the system.
I believe that TEACs solution is one manuf solution to these problems & I believe that they have kept the overall transport system as simple as possible but NO SIMPLER. This, of course, does NOT mean that their solution is simple; rather, it is only as complex as it needs to be. If you look at one of their VRDS transports, it is one serious work of art & engineering - I have SE transport in my Wadia.
There is one other factor that is part of the Japanese culture (that an American consumer will probably not understand): the Japanese are favourably disposed to over-engineering. It is in their products since the 1970s. Look at old Sony Walkmans, Sony TVs, etc: they look beautiful inside just as they do outside.
What I'm saying is that there is some element of over-engineering in the TEAC VRDS transports. However, the Japs take it in their stride as they have their home market in mind 1st. The fact that Wadia, the only American company AFAIK, uses it as well is just some side business for them.

there is 3rd aspect that plays superbly into the American manuf's hands: the US audiophile LOVES heavy weight audio gear! If it's heavy, it must be good! To that effect, name 1 European CD player manuf using the TEAC VRDS transport?

Once again as Lktanx wrote, computer-based audio has come a very long way in catching up w/ CD transports. The CD/DVD drives in today's computers are superbly robust & when they get done reading the data from the CD, it is practically 100% correct. CD/DVD drives have always been built with on-board SRAM & they have always been accompanied by hi-speed buses (IDE or SCSI in former years & USB 2.0 today) to carry the data to the CPU. This plays superbly into the hands of a PC being used as a transport for audiophile grade sonic quality.
I have personally pitted my 861 against the my friend's higher-end PC which he uses as a transport into a Scott Nixon Tube DAC+. His floor-stander PC uses a gaming chassis so it has a fancy blue flashing light, it uses higher speed hard-drives & a Lynx sound card. It was self-assembled & probably costs $2000-$3000, which is less than half the cost of my Wadia! Sonically, the difference is even less than the cost disparity. I love my Wadia & I won't part w/ it but it would be utterly foolish of me to ignore the "threat" PC audio is giving TEAC VRDS transports. You can ignore it but at your own peril.