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Transport vs DAC - Page 3

post #31 of 64
Quote:
Originally Posted by swiego
With the relatively low bandwidth of audio and the kind of fast interconnects we have at our disposal, it should not be a problem to buffer a huge amount of audio data and not have to worry about buffer underflows or overflows. We have fast readers, fast bitperfect interconnects and big RAM pools. Why aren't we buffering and reclocking everything?
I think this can be done. But it would require a new digital audio interface. This new interface will face compatibility and marketing problems. Very complicated business. If it is not going to be profitable who is going to push for it?
post #32 of 64
Well I've never claimed to be an expert on this subject (see my previous posts).

However, I have a couple more points to make.

The idea that the incoming bits might be coming in too quickly can be dealt with using a buffer in the DAC.

If they are coming in too slowly (and, again, we're talking picoseconds here), it's possible that a good DAC will buffer the input a bit before starting output.

If they are coming in at different rates, the buffer should again solve the problem.

These are very critical timings though...I am fairly certain that any jitter that *might* be present is nothing compared to the delays/interference/degradation inherent in the many parts of the audio system dealing with the analog signal.

The statement that somehow a transport can have an effect on soundstage, or any other aspect of the sound not related to extremely precise timing (in a non-musical sense) seems completely unwarranted based on the type of thing we are talking about here.

Regarding jitter from audio...I still go back to my video signal example. If jitter or timing were really a problem, don't you think it would be very obvious on computer video displays (which require data transfer rates thousands of times higher than those required for CD playback)?

Finally, what do the naysayers who don't believe a cheap CD reader can read a CD as well as a super-expensive CD reader have to say about something like a hard drive as a transport?
post #33 of 64
Quote:
Originally Posted by swiego
With the relatively low bandwidth of audio and the kind of fast interconnects we have at our disposal, it should not be a problem to buffer a huge amount of audio data and not have to worry about buffer underflows or overflows. We have fast readers, fast bitperfect interconnects and big RAM pools. Why aren't we buffering and reclocking everything?
My hard drive and sound card are probably doing some very nice buffering. Having hundreds of CDs (losslessly encoded as FLAC files) a couple of mouseclicks away is very handy too.
post #34 of 64
Quote:
Originally Posted by Scrith
Well I've never claimed to be an expert on this subject (see my previous posts).

The statement that somehow a transport can have an effect on soundstage, or any other aspect of the sound not related to extremely precise timing (in a non-musical sense) seems completely unwarranted based on the type of thing we are talking about here.
Once again you are dead on, of course that was just a small snippet of the whole article that you didn't read, but you went ahead and nailed it on the head anyway. Thats why i like you so much, you are here admitting that you don't know much on the subject, but you don't let that slow you down from making sweeping claims that transports don't matter. If only those damn engineers and reviewers were as bright as you are. They obviously have a lot to learn from you, I do hope you get in touch with them soon.
post #35 of 64
Quote:
Originally Posted by johnnysize
Once again you are dead on, of course that was just a small snippet of the whole article that you didn't read, but you went ahead and nailed it on the head anyway.
Did you happen to read this part, by the way?

"The North Star Model 192 CD transport is a standard CD transport, with some added feature: actually it can upsample the digital stream data from 16/44 up to 24/192 using the I2S format or up to 24/96 using the AES/EBU output."

In other words, it is manipulating the digital data. If you consider this type of thing to be the normal function of a CD transport, and you like such effects, you may be interested in the program I use for playback, Foobar2000, which offers DSP plug-ins that do all types of things to the digital data (like modifying it to increase soundstage, performing equalization, etc.)

The other link you gave (which you claim is a list of CD transport reviews) actually contains a large number of links to reviews of CD Players (with DACs built in), CD + DAC combinations, and stand-alone DACs. After some hunting I did find one that claims to be just a CD transport: the $25,000 47 Laboratory CD Transport PiTracer CD transport.

I am 100% certain that johnnysize would perceive some benefit from this transport over the typical $30 CD Player.

I am also 100% certain that I would not.

I have no idea what other people would think of it. To each his own.
post #36 of 64
Quote:
Originally Posted by swiego
Agreed. Nice article, but irrelevant in this conversation.
Which article are you two refering to? They both deal with the transport->dac jitter we're talking about although "everything you ever..." obviously also goes into adc jitter and jitter present in a cd vs cdr, etc.
The first article (rant) I linked to seems much more applicable to those who, like me, come to this from a background in computers and intuitively think bit-perfect is bit-perfect. Read AOS's article all the way through and then tell me why its not relevant.
post #37 of 64
Thread Starter 
I think there is no reason to get worked up over this debate, and I have a few things to add. First about reviewers. I wouldn't trust any review that appears in a magazine about high end equipment. They are almost ALL fantastic reviews about how this product or that will change the world. Just look at all the great Bose reviews out there. Critics are paid, and paid well for their comments, and often sued for slander if they offer a bad review!

Further, people like the best. An engineer might say that something is better and be right, but it also may be irrelevant. When playing a first person shooter people LOVE high frame rates. The truth is that the human eye cant distinguish between anything higher than 90 frames per second. However if a gaming company were to advertise that it could run a game at 90 fps it would go under. People demand that their new screaming machines run at 200 and 300 fps. I think its the same with audio. If you have a fancy looking transport, and an engineer says it is great, and a reviewer says it will widen your sound stage who are we, the mere mortals to argue? Based on quite a lot of reading i think that a DAC will definitely be my next purchase.

Mark

PS A big part of this decision lies in the convenience of a computer. I am not immume to the hype, and will someday buy a really nice transport. If for no other reason, than that they look SO cool, and I will feel like I'm getting better sound.
post #38 of 64
Ok I owned Rega Planet 2000, Arcam FMJ 23, Audionet ART V2 (~4000$ nowadays). And now have the AV-710. I've heard no difference between the digital-outs.
[EDIT]: The last test (between ART V2 and AV-710) I performed using AT-DHA3000 DAC/headamp & MDR-R10 headphones.
post #39 of 64
Quote:
Originally Posted by shooter_san
TIMING.
This calculation is probably inexact, but if you are transmitting 16 bits @ 44.1kHz, that is 2^16 * 44100 = 2890 Mbits/sec. Or, 346 picoseconds per bit. When transmitting data, you generally don't care if a bit arrives a few picoseconds earlier or later. (i.e. has "jitter") But when transmitting music digitally, you DO care if this happens, because that means the D/A conversion will happen a few picoseconds too early or too late. At the end of the day, that translates into a low-level distortion of the analog signal. And, given sensitive enough equipment and an attentive enough listener, it can be perceived.
This is great...one of the clearest, most concise descriptions of jitter I've read. Well done!

Quote:
Originally Posted by scrith
If they are coming in at different rates, the buffer should again solve the problem.
No, you're missing the point here...the audio signal stored in the buffer would still contain the timing errors. The best way we have right now to deal with jitter is to re-clock the signal.

Transports are responsible for clocking the signal in the first place, so they do play a role in the overall sound quality of your system. There are different types of jitter, however, and some of the worst is produced by the s/pdif interface itself. That's why its easier/cheaper to make a good sounding dedicated cd player than a transport/DAC pair...doesn't matter how good the transport is, jitter will still be introduced when the signal is sent to the DAC. The solution to this is an interface that sends the data and the clock as seperate signals, like I2S or any of the studio gear than runs a master clock signal through its own cable.

Quote:
Originally Posted by scrith
These are very critical timings though...I am fairly certain that any jitter that *might* be present is nothing compared to the delays/interference/degradation inherent in the many parts of the audio system dealing with the analog signal.
Here's where you're right on. I guarantee you that jitter exists...you can see it on an oscilliscope. However, how much jitter affects your listening experience is subjective. Like shooter_san pointed out, jitter doesn't sound like other types of distortion, to hear it you really have to train yourself what to listen for.

If you'd like to spend the time/energy to train yourself to be able to better point out the flaws in your system, be my guest. I'd rather enjoy the music. However, it is important for people in the digital mastering industry to be able to indentify jitter and deal with it, because like the Katz article points out, jitter at the ADC stage is permanent.

Also, if you own a Benchmark (or any of the multi-thousand dollar DACs that effectively deal with jitter) you can go ahead and buy the cheapest transport you can find and be in no danger of being ticketed by the audiophile police.
post #40 of 64
I don't know...

...well, I don't know if jitter is the only thing responsible for sonic differences with digital signal sources. Unfortunately I didn't spend enough time with the Benchmark DAC-1 to test the impact of different transports, but my Bel Canto DAC-2 which is said to be immune to jitter as well and even equipped with the same buffer circuit (?) reacts very pronounced to different transports (I have three at my disposal, and each of them has a distinct characteristic). Two of them use a Philips transport (although of different generations) with very low jitter values, but the best sound results from the McCormack UDP-1 with its not so great jitter behavior. The differences I hear are primarily in the presentation of detail and in the sonic-balance domain, but it's not just about dark or bright.

From what I've read digital signals from a harddisk drive should cause no sonic differences. But what do I know -- I have only one computer (with a lousy soundcard). And I don't know how to explain the sonic differences resulting from different CD transports, the only thing I can do is report my listening experiences.

post #41 of 64
Thank you, I know there are lots of people with actual experiences with high end transports feel the same way I do. Believe me I came from the exact same viewpoint as you scrith. I bought a Northstar M192 Dac and used it on a cheap sony dvd player. Of course when I put it in my system I thought it sounded better, then a while later I had to know so I set up a simple a-b with the dac in the signal and just the dvd player, I could not distinguish the two for the life of me. I would have just sold the dac, because it made me so frustrated but I figured I came that far I might as well see if a transport would make a difference, because it seemed like I read many a review talking about how transports do make a difference. So i put the transport in and there was a definite difference, It was a Conrad Johnson. I performed the same A-B style test with it in my system and the was a definite difference. I wouldn't say I was biased to want the transport to sound better in my system, I really didn't care. I buy things for a good priced used and usually wind up selling them for as much or more than i payed for them. I guess it is extremely important to note that this was done on a high end stereo not headphones. Im sure difference such as these would be almost non-existent in a headphone setup, headphones don't have much in the way of a sound stage or creating the illusion that they are performing in front of you. So if you are looking for a quality source for a headphone only setup, I wouldn't waste too much money, and IMO I wouldn't put too much in a dac either.
post #42 of 64
Quote:
Originally Posted by Scrith
Regarding jitter from audio...I still go back to my video signal example. If jitter or timing were really a problem, don't you think it would be very obvious on computer video displays (which require data transfer rates thousands of times higher than those required for CD playback)?
I have to disagree with the video example.
You know, movies are played at 24 frames per second.
This tells you how insensitive the eye is to signal variations in time.
Even in a LCD display, each pixel is refreshed at most at 85 Hz.
That means each each color is maintained for 118 ms.
The jitter we are discussing here is in the 200 ps range.
How is 200 ps variation going to affect signals changing only every 118 ms?
For CD playback, output signal is changed every 23 microsecond.
200 ps is almost 1% of 23 microsecond, so it is possible to see why audio quality may be affected.
While I am not a engineer, but from what I read a simple, standard buffer does not eliminate jitter problems. I can't offer the technical explanation, but there must be some more info out there.
post #43 of 64
Quote:
Originally Posted by johnnysize
I'm sure difference such as these would be almost non-existent in a headphone setup, headphones don't have much in the way of a sound stage or creating the illusion that they are performing in front of you. So if you are looking for a quality source for a headphone only setup, I wouldn't waste too much money, and IMO I wouldn't put too much in a dac either.
There's something we disagree on. Headphones deserve and benefit from high-end sources just as much as speakers. IME.

post #44 of 64
I like this discussion...thanks everyone for their input.

And now I will flip-flop and make a case for the importance of transports based on my experience.

I recently upgraded by computer's CD player to a Plextor DVD Burner. I noticed that this new drive is much faster at reading CDs than my old drive...not at specific points, but at the total read (rip) time of the CD. I also noticed it seems a bit better at getting past (without errors) problematic areas on damaged (scratched, because they were floating around in my car for awhile) CDs. Some of these CDs don't appear to be damaged, by the way...they look just fine, but for whatever reason they seem to be difficult to read accurately.

If I were listening to the music in real time, there would definitely be some playback problems on some of these CDs. I'm guessing that most CD players try to fill in the gaps with bad data (or just use the bad data as is), so it's quite possible that some do a better job than others. And as long as you're using a CD transport as your source, I don't think you can ever be sure that you are hearing a perfect version of the original data or some version that might contain some errors.

But...I get around this problem entirely by using my computer as the source. Once these files are ripped off the original CD and stored (losslessly) on my hard drive, I never have to worry about how well my CD transport performs, or whether it can read the CD fast enough.

And so, in my opinion, the best transport of all is a computer!
post #45 of 64
Quote:
Originally Posted by Scrith
And now I will flip-flop...
Geez, you're worse than John Kerry!

Quote:
Originally Posted by Scrith
And so, in my opinion, the best transport of all is a computer!
I haven't done any A/B tests with high-end transports (and I don't plan to), but I love mine. Absolutely the way to go in this day & age, IMO.
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