Today's Transport War: Significant Differences?

Pardales - A CD-Rom based CD player is actually just a computer-based system. Maybe we are arguing semantics. I believe what Alex is arguing is something entirely different though. I just cannot figure out what it is....

Steve N.

Seandtaylor99 - EAC does a great job of ripping. Foobar2000 and SRC do a great job of upsampling. I much prefer this to spinning CD's because of the lower jitter and superior sound quality.

Steve N.
Empirical Audio
Manufacturer

Drubin - with a computer external converter, the power supply can be just as quiet, whether it is USB or Wi-Fi.

Steve N.
Empirical Audio

The term "hard-drive" based source is a bit misleading. The hard drive is only a place to store the data. It might be stored in RAM in the future or 3-D magnetic memory. The term should be "computer-based" source.

You can read this paper comparing computer-driven to CD transport:
http://www.positive-feedback.com/Issue22/nugent.htm

In a nutshell, the computer has the capability to "feed" the audio device in any number of ways - streaming at high speed, native speed, bursting or network packets. Many of these data transfer techniques have intrinsic buffering in them, allowing the D/A converter to be fed with a fixed clock rather than a PLL. Doing this with a spinning CD is much more difficult. The Lavry concept is a good one. I'm not convinced that it is jitter-proof however. I have at least one customer that replaced his Audiophile USB with my Off-Ramp Turbo 2 and reported that the sound was more clear and focused driving the DA-10. This should not have been the case if jitter were completely rejected. However I do believe that Lavry's DAC is one of the better designs on the market for jitter rejection, even though I have not heard one yet.

The point is that there is at least the opportunity to generate a non-PLL clock to drive a D/A chip directly with Computer-driven audio. Not so with a transport. You might say: well what about a word-clock driven back to the transport? It turns out that the reality of this is much more difficult than the concept. Most modern D/A chips are not even clocked on the word clock, it is the bit-clock or the master clock. To drive a DVD player for instance, you would need a 27MHz clock from the DAC to the Transport. Then you must divide this down inthe DAC to synthesize the clocks needed for the D/A converter. Then, in order to make this work, the D/A must resolve the phase difference of the Transport signals and the local non-PLL clock. The phase of these signals will change with the digital cable length, delays in the transport circuitry and clock generation etc.. The total timing budget is about 75 nsec for 24/96 signals, assuming S/PDIF interface. The slop in the reading of the bits from the optical head will probably eat-up most of this budget. The only way to pull it off is probably to FIFO buffer the data coming into the DAC to allow it to slop around. I'm not saying it is impossible, just more difficult and involves tight coupling of the transport and DAC. Mixing and matching transports and DAC's would not be possible. The Meitner system got around all of this by using an I2S interface. This is much simpler, but still relies on a PLL.

Steve N.

"Hopefully in the future the time will come when proper technology will be developed so one is able to load favorite music onto a computer based audio solutions and play it back while achieving the same audio quality as with the classic dedicated stand alone digital front-end is possible today"

I'm more than optimistic. I'm already there.

Steve N.

"A computer is quite evidently capable of preserving the 1s and 0s, since it's able to install an operating system from a CD-ROM. The computer might have jitter and noise on the output, but it's not rocket science to buffer and reclock data, to completely remove the timing jitter from the computer."

Exactly my point. It is easier to do this with a computer because the data can be fed in a number of different ways that lend themselves to buffering and reclocking. The data is not necessarily coming on-the-fly like it is from a CD spinning at the native rate. You cannot re-read a block of data on a CD or read-ahead at high-speed and store the data in blocks. You have to provide the data on the first pass and continuously without breaks in real-time. If a CD-player is doing buffering and high-speed transfers of blocks of data, then it is actually a computer-based CD system, not a classical CDP at all.

Steve N.

Alex - I dont know what you mean by "Noiseball", but I do know that once you remove the digital and analog conversions from a typical computer chassis, whether it is using USB or Wi-Fi, this provides the opportunity to generate an extremely low jitter data stream.

Likewise, if you speed-up the CD player and make it essentially a CD-ROM drive and buffer the data, you again have the opportunity to generate an extremely low jitter data stream.

As for the computer sounding unsatisfactory, you obviously have not heard a good computer source yet. This is like listening to a $60 Walmart CD player and then proclaiming that all CD players sound terrible......and BTW, the Olive will only challenge good CD players once it is modded.

I have superb native 24/96 tracks mastered from tape in .wav format. I would like to see you play these on a CD player.

Steve N.

Jsadurni - too bad about your experience with the SB. I have found that USB audio is much better quality than Wi-Fi (even though I sell an Off-Ramp Wi-Fi), but dont expect miracles if you buy a cheap converter. USB audio can outperform most transports IMO, but ONLY if:

1) you use a custom S/W driver - only comes with certain converters
2) you avoid the TI 270X chips - most of the converters are based on this
3) the converter is clock by a low-jitter clock, such as Superclock
4) you use a PC and SRC upsampler
5) you use the right ASIO plug-in

I know it's a lot to consider, but the results are well worth the effort.

Steve N.
Empirical Audio
Manufacturer