Reference Transports: An overall perspective

Mike, I believe Lktak is referring to what nearly all Universal players use. Models like the Denon 3910 and many other Universal players read at something like 10x rate and buffer to SRAM, then reclock out. Some carry this buffering to redbook CD as well. In theory, if your error correction software is infallible and your reclocking extremely precise, this should result in a perfect bitstream. Questions are: 1.) is adaptive error correction good enough. 2.) what influence does mechanical vibration have on (1.) and on the overall performance of the player/transport. I wish I could answer these... I cannot, but I too have heard significant and very meaningful differences among transports.

Lktanx, so if error correction is only for gross errors, then it seems logical that the transport becomes a very important part of getting the data correct, particularly if it can minimize the random errors that occur in all physical systems. If errors are correlated, then adaptive error correction would be helpful, but how are random errors corrected once they occur?

I agree that once the data is read to RAM, the only meaningful influence on the digital signal, other than digital filtering and D/A conversion, is the precision of the clock. Still, to get the data into RAM you need to read it via a transport, and unless you're claiming that all transports are perfect, I don't see how the transport is not a meaningful link? We could debate the significance of this link, but that's another issue altogether.

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.

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

Bombaywalla, the depth of my knowledge in the area of digital audio is not that great...I admit that. I am not a digital engineer. You are also correct that I didn't prepare for this discussion. However, it does appear that you have narrowed this discussion to just the reading of bits off the disk and have in some ways contradicted yourself. I am probably to blame for the former as I focused my response to Lktanx on read errors. My "ex-tempo" response was perhaps offbase or at least, too shallow?

Perhaps we have been talking past each other (maybe not?), but my initial response to Lktank was a reaction to this statement

In a modern properly designed player, transports should make NO difference to the sound.

If this were true (and I view the transport -correctly or incorrectly- as everything from reading the disk to just before the digital filters, including motors, power supplies, etc to accomplish this) then any modern transport should sound IDENTICAL to the next...not almost as good or practically as good, but IDENTICAL. The issue of cost/performance is moot...they must sound identical. A Sony, a Wadia, a Toshiba, an Esoteric, etc should all sound the identical if feeding the same outboard DAC, right?

Forgive my non-technical, empirical approach here, but my experience with the effect transports have on the sound in my system were with the ARC CDT-1, Theta Data Basic, and a Pioneer DVD player using the digital out...all using the same Kimber digital cable feeding a Theta GenVa. The differences were not subtle, even between the Theta Data Basic and ARC CDT-1. Both were noticeably better than the Pioneer player. I realize that there are variables still unaccounted for in this experiment; however, the ARC and Theta did not read to RAM and the Pioneer did.

I asked why would Esoteric spend so much money recently on developing and manufacturing the VRDS-Neo transport when they were going to read the data to RAM? On your first point, you said something along the lines that the clamping system they use eliminates/reduces CD wobble which reduces the "surges in electrical current drawn from the digital supply by the laser optics electronics". You went on to say that "this has the effect of dirtying the digital power supply & this crud pollutes everything it touches". This explanation sounds reasonable and reinforces my belief that the design of the transport is an important part in the design a good digital player. Would you agree? Would using a well-designed linear power supply for the laser optics accomplish the same thing? I don't know...I'm asking the experts.

I'm not so sure that Japanese culture has a great deal to do with Esoteric’s approach to their recent Universal players. I spent a year working for a Japanese manufacturer in Japan in the mid 90’s. I would say I’m fairly comfortable speaking of their culture. High-end Audio is a culture of it’s own whether in Europe, Japan, or the USA. Your statement that Japanese mfg's have been overengineering since the 70's doesn't hold water. The initial offering of all new technologies are usually over-engineered. RCA made some pretty substantial VHS players in the 70’s also. You think the iPod will continue to be housed in the metal chassis for much longer? I’m fairly certain that Esoteric did not over-engineer their recent transports by such a large degree for purely marketing purposes. This would be alot of expense and effort if it made no difference to the final sound. I've found Japanese engineers extremely practical in general and would fully expect them to focus their attention and investment on better digital filters, analog stages, and DACs if the transport made no difference to the sound. Certainly, they wouldn't tie the entire success or failure of a product to a multi-thousand $ "gimmick".

Finally, I have no beef with "computer-based audio" and I'm sure it sounds great. My main point is that there are differences in transports. Whether this is due to corrupted power supplies, read errors, or some other factor...there are differences. I am NOT saying that the differences in transports are massive or that they are more significant to the sound than other parts of the digital playback system. Your statement that

you are also blowing the importance of the transport -w-a-y- out of proportion, if I may say so.

is entirely misplaced. I said that I have heard meaningful differences in transports in my first post...that's the extent of my "blowing the importance of the transport -w-a-y- out of proportion".

Are we talking past each other or are we at least on the same page? Thank you for educating me on some of the technical details I may have misunderstood.