SACD -- an illogical choice
Apr 17, 2003 at 1:15 AM Post #76 of 90
There is a very good explanation of how asynchronous sample conversion works and theory behind it in AD1896A datasheets (www.analog.com), for those that are interested and have necessary technical background. You can also see a jitter rejection graph of its digital servo loop, which is very similar to a reclocker. However, reclocker does not alter the signal in any way while async sample converter does. On the other hand, ASC has much lower lock-on times (my reclocker takes almost 10 seconds to lock!) and is very flexible - works with any sample rate while a reclocker works with only one unless you have multiple crystals (so you're stuck at say 44kHz and can't decode even 48kHz). Reclocker also has a chance to lose a sample or read it twice while ASC cannot.
 
Apr 17, 2003 at 5:35 AM Post #78 of 90
Oh yeah, they did. That's why it's discontinued and have been replaced with... AD1896A!! Funny enough, even that one has problems - if you use it in bypass mode with less than 24bits if I remember correctly. Anyhow, otherwise it should work fine.
 
Apr 21, 2003 at 5:18 AM Post #79 of 90
Quote:

Originally posted by Orpheus
take your favorite redbook 16bit/44khz CD.... if we take that CD and convert it to SACD, would it sound better? of course not!


I'm not sure this is true. Case in point, the dCS Elgar/Purcell/Verdi system has an "upsampling" option that does exactly that, and in at least one review, was the primary choice!

And also -- I've noticed that any time that anyone says anything that tries to point out other superiorities of one vs. the other, that you come up with the "that is not what this thread is about" point. Isn't it? I would have to disagree. The context of your discussion is what is best for you, as a consumer. It's much more holistic than trying to divine what went on behind the scenes. Isn't it pretty much "if it sounds good, it is good"? I mean, hypothetically (and I am not saying this is so), if SACD were so superior that even if it was recorded in PCM at every stage of the way right up until the last point, then converted into DSD, and that was far-and-away better than high-bitrate PCM, then wouldn't SACD be the better choice?

Why would engineers work in PCM, then deliver in DSD? Because the only tools available in DSD are ADC's and...well, that's it, really. In PCM, there are mixing boards, reverbs and other effects, synthesizers, etc. Whole computers. So that scenario really isn't that far off the bat.

Let's get back to music for a second -- isn't that like saying I would only like to listen to musicians with whom I share a life philosophy? No, I really only care about the music, who cares how it got to be where it is, or why.
 
Apr 21, 2003 at 5:33 AM Post #80 of 90
well, the pretense for this whole discussion is logical and scientific reasoning.... hence the usage of the word "logic" in the thread title.

...there have been many threads arguing which sounds better. that's old. .........and i have never said that SACDs cannot potentially sound better than DVD-As..... potentially!......

that is why i always say that various comments are not really appropriate for this thread....., dusty. you mention that elgar combo...... well, see.... there are debates on that too. theoretically, upsamplers should not make any difference. it's that kind of thing i want to talk about.... WHY it does not make sense to use SACD.... just like it doesn't make sense to use an upsampler. i am not saying that it doesn't work.... it just doesn't make sense that it works. get it? there are many unexplained phenomenons......

i guess one issue here that i was trying to point out was that some things that audiophiles take for granted, like the famous, "if it sounds good, it is good..." are fallacies.

no..... if it sounds good, it does not necessarily mean it IS good. it only means you THINK it is good. people have different tastes....

but the only thing you can really carry an intelligent debate on are facts. ..........so that's why i wanted to leave subjective opinions out of this thread.

but of course, if SACDs sound better to you, then that's what you should buy.
 
Apr 21, 2003 at 6:20 AM Post #81 of 90
Quote:

Originally posted by Orpheus
theoretically, upsamplers should not make any difference.


Says one theory. Mine says otherwise. Quote:

i am not saying that it doesn't work.... it just doesn't make sense that it works. get it? there are many unexplained phenomenons......


I think so. You are in the "Joe Bloggs" phase of asking a lot of questions in order to try to understand something better, 'ey? Quote:

i guess one issue here that i was trying to point out was that some things that audiophiles take for granted, like the famous, "if it sounds good, it is good..." are fallacies.


Whoa! Quote:

no..... if it sounds good, it does not necessarily mean it IS good.


As opposed to what? There are only opinions. There are no absolutes. Quote:

it only means you THINK it is good. people have different tastes....


Agreed, completely. Quote:

but the only thing you can really carry an intelligent debate on are facts. ..........so that's why i wanted to leave subjective opinions out of this thread.


You can't. Or rather: IMHO, you can't.
 
Apr 21, 2003 at 9:09 AM Post #83 of 90
>>Theoretically, upsamplers should not make any difference.

Yes they do because they modify the samples. E.g. AD1896 upsampling chip conceptually samples the original digital signal with factor of 2^20 and interpolates it. What you hear are not the exact originals samples from your CD. However differences in this information are likely far beyond resolution of human hearing - they are limited by issues such as number and precision of filter coefficients and calculations - so you might think at first that they don't make any difference. You cannot add information that didn't exist but you can still have different final result because of different takes on practical issues with D/A conversion (such as analog filters, jitter etc.) that upsampling brings to the table. These differences in ways the final sound is created are explained in posts of several people above (and in chip datasheets). So in theory there are differences, but what *is* subjective with this whole process is whether one can hear those differences or not and that is something that cannot be resolved logically.
 
Apr 21, 2003 at 4:52 PM Post #84 of 90
Quote:

Originally posted by aos
>>I don't know about the jitter reduction (some say upsampling increases jitter),

I haven't heard that before. One of the reasons for existence of these chips is to reduce jitter. Datasheets are chock full of measurements to show that, as well as theory behind it. <snip>


Can you point me to something which explains theoretically why changing sample rates will reduce jitter?

As far as I understand it, jitter is introduced in sampling the data so changing the sample rate will effectively mean two clocks to reduce jitter from ??
confused.gif
 
Apr 21, 2003 at 6:57 PM Post #85 of 90
Regarding jitter, consider the simplest possible type of upsampling: synchronous upsampling (the DAC simply reads each incoming bit multiple times). For this example, let's assume 4x upsampling. Let the ideal bit times be {o, o+d, o+2d, ...} Introduce random amounts of time-domain jitter: {o+j1, o+d+j2, o+2d+j3, ...} Now upsample by 4x:
{o+j1, o+j1, o+j1, o+j1, o+d+j2, o+d+j2, o+d+j2, o+d+j2, o+2d+j3, o+2d+j3, o+2d+j3, o+2d+j3, ... } This is equivalent to the DAC receiving the following un-upsampled data stream: {o+j1/4, o+d+j2/4, o+2d+j3/4, ...} Thus, we've reduced jitter by 75%. Asynchronous upsamplers can do even better.
 
Apr 22, 2003 at 1:57 AM Post #87 of 90
Quote:

Originally posted by Orpheus
--do you mean, me personally, as in Orpheus cannot "carry an intelligent debate?" is that how i should read that statement? please clarify.


Nononono, not at all! I meant, you can't "...leave subjective opinions out of this thread."
 
Apr 23, 2003 at 4:07 PM Post #89 of 90
Orpheus:

I wonder if you've looked at this thread lately. In it, I offer another reason that SACD might be illogical -- not sonically but economically. I also suggest that DVD-A might well become dominant outside Japan and the US.

Keep in mind that I say this despite my owning an SACD player [] (the Philips 963SA).
 
Apr 23, 2003 at 6:54 PM Post #90 of 90
yeah.... backwards compatibility is a great thing. like for instance, if programs for Windows XP wouldn't work with 98 or 2000, development for XP would be very slow because no one wants to lose the market for older systems.

and yes, ultimately i don't think most consumers care which is the better technology, SACD or DVD-A. they surely don't argue about it like we do.
 
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