Today's Transport War: Significant Differences?

Seandtaylor99 - Steve has listed the main software components. Also ensure that for whatever sound output device you use, make sure you have the latest software drivers and use a dedicated computer with latest software (Windows XP SP 2). In foobar2000, use either kernal streaming or ASIO for playback.

I much prefer this to spinning CD's because of the lower jitter and superior sound quality.

Sure! :-)

Regards,
Alex

Thanks Steve.

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

Cics, what computer programs are available that would allow you to rip, upsample, and potentially word extend and dither redbook CDs ? It seems like an interesting direction to go in.

What is Jitter? is an interesting read and offers a good reason for why transports sound so different.

I have setup a computer transport with great success. Its easy to get started but more effort/learning is needed to get best performance. After comparing my setup with some exotic (& very expensive) front-ends (Wadia 9 series, Esoteric P03/D03 & MBL Ref trans/DAC), I don't have a need to upgrade. Sound is superior to Wadia (bad dealer setup most likely here) & Esoteric (detailed but lacks musicality). MBL was excellent and couldn't be faulted but I don't need it.

It seems that computers are far better at upsampling than hardware based algorithms within a transport and/or dac. Upsampling after all is a computing function and doing it correctly, needs lots of processing power.

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.

Steve N.: "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."

I guess this might be what I really want to know. Is it evolution, or, maybe convergence of technologies?" What would really be a classical, digital transport?

If we look at this, it may help us see where this is going...

"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.

Js I agree that the transport sound can be even more important than the Dac...well maybe until this Altmann piece. I need to try some other drives to know for sure. I'm always in search of something better but right now this dac with a JVC dvd player sounds better than my last two rigs. Always in progress/I hope..Tom

"I guess If you destroy the original signal (say in a bad computer or a crappy DVD player) and then reconstruct it on the DAC, the result is not the same as if the signal is kept complete (as much as possible) from transport to DAC. "

How are you destroying the signal ? The digital signal is nothing more than 1s, 0s and timing information. I'll bet that even the crappiest DVD player's digital output has 1s and 0s that EXACTLY match even the most expensive transport. The $20 DVD-ROM drive in my PC seems able to extract and install windows XP without a single bit error, and it can do this while reading the CD many times faster than an audio CD has to be read.

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.

Almost all DAC manufacturers will tell you transport doesnt matter, EAD manfacturer told me the same, because of the digital-flywheel thingy, Transport is very impotant I would say even more than DAC...

I guess If you destroy the original signal (say in a bad computer or a crappy DVD player) and then reconstruct it on the DAC, the result is not the same as if the signal is kept complete (as much as possible) from transport to DAC.

Thanks for that post Alex, it clears up a lot of things for me.

I hope the Nova memory player is indeed much better than a 10k transport, if that is the case we can say good bye to vinil, I hope its not just the next SACD!!!

Seandtaylor99 - Thanks for the link, interesting read.

Grant a friend of mine whose products were on display at RMAF was brought down the Nova Memory Player you mentioned above. He heard this player on his system setup at the show after hours. The Nova player was compared heads up to the 10k player they were using in their listening room..he said he wants to purchase the Nova..The copy he made on the Nova and then played back on the other player sounded much better than the original cd played back on either machine. Electro mechanical jitter error correction all of that the Nova guys claim is pretty much gone.Playback from the memory chip internal of the Nova player is even better yet. The Melos crew is back! I recently purchased an Altmann Dac from Germany. Sounds wonderful. Altmann claims with his circuit redo's that the transport makes little or no difference..my listening comparisons so far are making me listen and look harder at transports differences when played thru this little 12volt wonder.Tom

Aplhifi: if I'm understanding you correctly, you're saying that a vibration/error free front end as you suggest reads different data from a disc than would a lousy CD-ROM drive in a computer? Has this been tested, e.g. is it possible to somehow capture the digital data from a such a transport and compare it to a standard rip from a CD-ROM drive on a computer? Now that would be an interesting experiment! :)

If they are indeed identical, what then is producing the difference in sound? You stated that jitter is not much of an issue anymore, what else could be a factor if we assume that the DAC is identical?

I'd really welcome a discussion on this, it's so hard for me to understand what the problem really is. It should be so simple I think, but demonstrably it isn't since I've too found significant changes between various CD transports connected to the same DAC using the same cable and playing the same disc. How is this possible?

Thanks!

The Noiseball (aka computer) converts audio data many times, uses questionable performance clocking, has switching mode power supply and uses poor interfaces (mostly USB and Wi-Fi packets or combination of both) to transmit audio data to an external DAC. It does not really matter if the USB signal is converted to S/PDIF, I2S or anything else, it still comes from that same USB port! Same applies for Wi-Fi connection where the middle of the audio track may be sent first and then the beginning of it and so on in random packets which are then decoded and reconstructed by a DSP (talk about error correction). There are some nice pro-audio computer cards available allowing much cleaner data transmission and slave mode to the DAC clock, but please realize that all you slave to the DAC is the clock of the computer card DSP, nothing else.

Even a cheap $149 universal player spins the CD, SACD or DVD-A at higher speed allowing for memory buffering using both FIFO and large SDRAM buffers which results in “jitter free” clocks and “bit perfect” data. It is not true that the DAC in a CD/DVD/SACD player has to be PLL-ed (and what’s up with the “evil PLL” thing? Latest PLL techniques are great achieving as low as 30pS jitter!). Good example that comes to mind would be the famous, faulty and long discontinued Philips SACD1000. This player has its main 16.9344MHz non-PLL audio master clock (low noise powered) next to its DACs, the perfect scenario. This non-PLL, low jitter master clock oscillator is also clocking the audio DSPs. Then, PLL is used to generate the 27MHz clock for the video circuit. The SACD1000 spins the CD at much higher speed and uses combination of FIFO and large SDRAM buffers. The “jitter free” and “bit perfect” PCM data/clock transmission in the SACD1000 is carried by our beloved I2S but without any data conversion or long cables and connectors resulting in about 5-6 inches cleanest possible signal path. WOW, isn’t this amazing! It looks like the perfect CD player, the perfect solution, right? Well, I am sure that many around here know for a fact that the stock SACD1000 performance is nothing to write home about, although it was a nice machine for its time. The moral of the story; not everything is as easy and simple as it looks.

IMO and IME, a carefully optimized (key word), vibration/error free “classic” digital front-end using memory buffering and latest error correction engines, with built-in dedicated, specially designed DSPs, shortest signal path, no data conversions to completely irrelevant to audio data transmission formats, ultra low jitter clocking and low noise power supplies simply can not be outperformed by computer based audio, at least not for now. 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. So let’s stay optimistic.

Regards,
Alex

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.

Jeff, in theory you're correct, but in practise I believe you're wrong, and the principal reason is due to the poor design of the whole transport - interface - DAC setup.

I agree with you that the 1s and 0s get to the DAC with no problem, but the issue is the DAC clock.

For high quality audio the DAC master clock should have very low jitter. Unfortunately the traditional method, where the CD transport has the master clock, and then the DAC has to try to reassemble the clock from an SPDIF or AES EBU data stream is a very poor scheme, and is entirely responsible for the fiasco of multi kilobuck transports and digital cables.

If DAC had been designed with low jitter master clocks, and the transport was slaved to the DAC I think we could have been using $20 CD rom drives, and ZIP cord digital cables right from the start. Many companies have implemented proprietary mathods to allow their transports to be slaved to their DACs, but it has never really caught on.

It would appear to me that Dan Lavry's approach of using a RAM buffer and a low jitter oscillator in the DAC is the best engineering approach to solve the bad situation. With enough RAM it wouldn't matter whether data were to come in from a PC (via USB, or ethernet) or from a transport (via toslink, SPDIF, or AES EBU).

I've never heard his DACs, they also may be compromised in the implementation, I don't know, but I've found the whitepapers on his website extremely informative.

There are several papers about 1/3 way down this weblink.

http://www.lavryengineering.com/supportpage.html

I'll be trying the North Star 12S interface shortly. I have had the transport for a while, and now just bought the DAC. It will be interesting to see how it compares with my existing set-up.

I've yet to see either camp come up with any meaningful data that would justify my $'s (i.e., if you can't measure it on the back side of a d/a converter then I doubt if you can hear it). Something I think audiophiles overlook is that digital data transmission is very forgiving by nature, as long as the bits get there at about the right time and at about the right magnitude, well designed equipment on the recieving end can reconstruct and reclock the 1's and 0's. You could watch a satelite hdtv and note the crystal clarity from the much higher speed digital data transfered back and forth through the atmosphere, and then decide if you want to worry about the bits from your transport crawling slowly to your dac across a couple feet of cable.

Steve Nugent of Empirical also says the best to be had is I2S. The Northstar transport with its' I2S output tweaked into a DAC with I2S input is the way to go, according to Steve. He says I2S properly implemented is "magic".

My reading of the POV of both Empirical and APL is that their preferences are independent of price, or nearly so. Empirical believe that hard-disk systems give us an opportunity to achieve better sound (by reducing jitter to practically nothing) than we can ever get from a transport spinning a disk. APL are vague on the specifics but seem to feel that the "environment" of a computer is far too polluting to yield seriously good sound. Steve says there's only jitter, nothing else to be concerned with. Alex had not yet weighed in on that. I respect and admire them both and hope I have not misstated their positions. Great stuff!

For me the sonic differences have been largely insignificant compared to the difference in convenience of having an entire library of music at my fingertips to mix and match as I choose. I find I do more listening this way rather than having to get up and change the disc every time I want a change. Call me lazy, but I'd rather listen futz around with my software and hardware.

I'm not sure if what you (this thread) are referring to is the one-box HD solutions, as Tvad mentions, and or PC-based audio as I'm using.

Let me go a bit more into how I view the differences as it may be revealing to those who choose to be more discriminating about these details. I've found that when you get beyond a certain threshold of investment, that the gains you get for dollars invested become very rapidly diminishing. Yes, I can hear the differences between my friend's $7K DAC and my outdated NOS DAC which can be purchased for $500-600 on the used market. But those differences are pretty small, IMO, compared to the HUGE difference in price. If you have the money, and want to invest it that way, have at it. I'd personally rather invest in more music. If I had invested additional money in small gains in hardware I think I'd end up feeling it was a poor investment for the gains got, but then everyone has their own threshold, and their own standards. The few times I've done side-by-side comparisons going into the same DAC, the differences between transport and PC/HD audio were not significant to me, nor were they consistent enough to pick out one specific, consistent fault going one way or the other. I would not put my system up there in the realms of great high-end reference systems, rather a modest entusiast's system, judged by pretty discriminating ears. Take it for what it's cost you to read this and the fact that you likely don't know me from Adam.

Marco

Very good point Ehart -- clearly a conversation about this topic in the cost-no-object realm would be different than in the budget and mid-price levels.

A few of the organizing issues seem, to me, to be:

1. The "rip" or how data is read

2. The quality of bits: are all bits equal?

3. And the whole USB/SPDIF/I2S thing.

There are probably other organizing characteristics that are important, this just reflects where I am in my understanding.

Hi,

Price level affects the answer to this question. You'll see quite a few comments where people say that their hard-drive-based transport "nearly equals" or "equals" their $3000-$5000 conventional transport. I take this to mean that the best conventional transports are still as good or better than hard disk based audio.

For those of us that are in the more common $500-$2000 CD player range (Rega, Arcam, etc.) the balance seems to tip towards hard disk based audio. Sound quality of the hard disk solutions is at least as good, and the convenience is killer.

There are currently relatively few hard disk based options (compared to conventional CD players). I think we will continue to see many more of these units coming out, and units from Sony and other mass-market manufacturers before too long.

- Eric