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Upsampling DACs - Page 2

post #16 of 106
Oops, my bad

Now then... that means, unless someone knows the answer here... that i'm going to have to trawl around the internet looking for what exactly the difference is between up, and over sampling (where of course you can have it at 8 times or more)...
post #17 of 106
Quote:
Originally posted by taoster
is there a difference between a DAC and an upsampling DAC?
Yes. A DAC just converts the 16/44.1 to analog. An upsampling DAC converts the (digital) 16 bit/44.1 kHz signal to a (for example) 24 bit/96 kHz signal, then converts it to analog. This makes it easier for the analog low-pass filter to deal with.

Now you may think to yourself, what's the point? You can't introduce information that's not there?

Ah, but you can.

As kelly likes to say it, it's not so much that the algorithm is introducing information, as it is getting "less in the way". It introduces fewer "nasties".

Take, for example, a 22 kHz signal. It basically looks like a square wave before the analog filtering. Upsampling will make it look more like a sine wave. The "corners" are less sharp.

The overall effect is a smoother signal.

As tuberoller said, and I too feel the same way, at this point, I wouldn't get something that didn't have upsampling. I'm at the point where I'm comparing upsampling algorithms (listening to the GW Labs DSP right now). I'm not sure I would go 24/192, now that I've already gone 24/96, but that's because I'm already most of the way there. We are definitely talking about "that last little bit" here. But to me, that makes all the difference in the world, especially in terms of long-term listening fatigue. (And I listen for hours at a time. At work, on a good day, I can go through a stack of CD's, one right after the other.)

Download this file and read the second page, it explains it pretty well.

EDIT: I forgot to answer the implied question -- is there an audible difference between an upsampling DAC and a regular one? Well, yeah, sure, a well-designed DAC can outperform a badly designed upsampling DAC, but I haven't heard the latter.
post #18 of 106
Just to reiterate what Duncan says about the Cambridge Audio S700...

This DAC is an ABSOLUTE STEAL for only £79....

Anyone considering a DAC should definatley check this one out.

This product retailed at £300 originally and not only do you get the DAC but also
it is built into an isolation platform for free !!

Best value for money I have EVER had....

..Oh, and you also get HDCD decoding thrown in !...
post #19 of 106
Quote:
Originally posted by Duncan
Now then... that means, unless someone knows the answer here... that i'm going to have to trawl around the internet looking for what exactly the difference is between up, and over sampling (where of course you can have it at 8 times or more)... [/B]
Took me the longest time to figure this out*. Oversampling means they play the same sample repeatedly; upsampling means they interpolate the values. So

oversampling == 16/44.1 -> 16/88.2 (2x oversampling), 16/176.4 (4x oversampling), etc.;
upsampling == 16/44.1 -> 24/96, 24/192, etc.

Oversampling is still good, because it still smooths out the frequency, but upsampling is better, because it also increases the bit resolution, so it's just more accurate (depending on how it's implemented).

*EDIT: It took me the longest time to figure this out mostly because the term upsampling in its current incarnation is fairly new. They used to use upsampling and oversampling interchangeably. You also get a lot of pages on how it's done, when all you care about is what it is.
post #20 of 106
Thank you for that Dusty... I now understand

Oh, and something of interest for people looking at the S700 DAC...

Quote:
From the Cambridge Audio S700 Product Page...
The product's famous SAA7350 (DAC7) DAC chip and PMD100 HDCD¨ digital filter are implemented in a no-compromise design featuring no less than 15 separate regulated power rails and both optical and coaxial connections
I've looked on the internet for what DAC7 is, and couldn't find anything apart from repeated quotes and reviews saying that the Marantz CD-17KI retailing at £1,100 ($1500) contains the DAC7 configuartion...

I'm guessing that that makes my two box setup sound nearly as good (or maybe better depending how well Marantz implemented this design) as the CD-17KI?!

[Edit]

More research takes me to these excerts... (if it makes any more sense to know, all of the FS references... i.e. 192xFS, on the webpage the S is in subscript format)

Quote:
Digital to Analogue Conversion
The Digital to Analogue converter stage is constructed around the SAA7350 and TDA1547 from Philips. The SAA7350 is used to up sample and noise shape the digital audio data stream, producing a 1-bit Pulse Density Modulated (PDM) output signal for conversion back to analogue by the 1-bit DAC. It takes in data from the digital filter at 8 x FS, and then outputs it at 192 x FS. This oversampled data stream is then carefully routed to the TDA1547 1-bit DAC. The clock for the DAC is taken directly from the clean master clock, which is again carefully routed away from digital audio data tracks...

...Present noise shapers run at rates from 64 x up to 192 x FS. The higher the sampling rate the better, for obvious reasons. This is why the DAC20 uses an SAA7350 which runs at 192 x FS...

...Noise-shaping is used to reduce the noise in the baseband, which has resulted from the inability to oversample at a high enough rate, by moving it up to frequencies outside of the baseband. The SAA7350 uses 3rd order noise-shaping to achieve this objective...
from a Tag Maclaren White paper site... Also it mentions the other chip quoted on the Cambridge Audio website...

Quote:
...PMD100 eight times oversampling filter

So, As Dusty said... not quite as good as full on UPSampling... but, it seems like I have the best of both worlds?!?!

Does this mean that the Cambridge Audio S700 DAC and its implementation of the Philips SAA7350 and PMD100 chips is actually kinda cool?

Thanks
post #21 of 106
Quote:
Originally posted by Mel4
This DAC is an ABSOLUTE STEAL for only £79....

Anyone considering a DAC should definatley check this one out.

This product retailed at £300 originally....
Mel4, I think (although don't quote me on this ) that the £300 quoted on the Richer Sounds page is the current retail value of the unit, three years after it was first manufactured...

This American company is still selling the unit at $750!!!!
post #22 of 106
Upsampling
Very simply put, the advantage of upsampling (24/96, 24/192 etc) and the reason it sounds better is that it allows removal of noise and distortion from the DAC process in ways that don't negatively effect orignal music signal. CDs sound much more natural.

This is the reason older DAC designs always had a hard unnatural sounding treble because of noise and distortion introduced by the DAC process. The infamous brickwall filtering employed in older designs major culprit here, have very negative audible effect on music signal
post #23 of 106
I am still an ART DI/O fan. It's small and it's cheap. It rocks. I've sent mine off to Bolder Cable to have it modified and I'll post my thoughts on it when I get it back. However, from my experience thus far, the unmodified ART DI/O is not in the same class as the modified P3A. The difference between these two units is HUGE. I sincerely doubt the ART will rise to the modded P3A's level via the Bolder mods but hey, if it does, I'll be a really happy camper.

If you are limited on funds, the ART is $125 and the mods are $260. For $385, I suggest that the ART is completely unbeatable. An upgraded PSU will also be available but I'm not sure of Bolder's price for that yet.

So the P3A is much better... but cost much more. It's all relative.
post #24 of 106
Quote:
Originally posted by taoster
Wheres all the ART DIO fans gone?

is there a difference between a DAC and an upsampling DAC?
The ART DI/O is not an upsampling DAC, strictly speaking. However, for my opinion on the ART DI/O with an external upsampler, see my post on the GW Labs DSP in the cables etc. forum.
post #25 of 106
Not really in the context of this thread, but may still be of use...

I bought a completely standard no brand (video) BNC cable for my DAC today and the sound compared to the optical... WOW!! The slight sibilance there was with vocals is now gone... the soundstage has filled out somewhat, and the mids... hmm... lovely mids

I think its common knowledge that Co-Axial (or in my case BNC) cables are better than optical... but I didn't realise by how much until I just heard it with my own ears... and with a cable that I can't even guarantee is a true 75ohms!!

Do things improve further still if you get a dedicated 75/110 ohm cable??

Thanks
post #26 of 106
Quote:
Originally posted by Duncan
Not really in the context of this thread, but may still be of use...
As a moderator, yes, I'd think you'd take "not really in the context of this thread" to mean, "Hey, maybe I should start a new thread instead of veering this one off target."

Quote:
Originally posted by Duncan
I think its common knowledge that Co-Axial (or in my case BNC) cables are better than optical... but I didn't realise by how much until I just heard it with my own ears.
I agree that coax/BNC are noticably better than optical. That some Sony products are optical only (because they own the format) is ridiculous. Definitely do go coax when you get your new DAC.

Now back to the DAC...
post #27 of 106
BNC connections are even better than coaxial. Coaxial doesn't always guarantee the 75 ohm connection throughout...specifically at the connectors.
post #28 of 106
Quote:
As a moderator, yes, I'd think you'd take "not really in the context of this thread" to mean, "Hey, maybe I should start a new thread instead of veering this one off target."
Well... if you were to want to buy some amazingly well specified upsampling (to keep this in the correct context) DAC that only had optical out... then you'd obviously be missing out on something... so my post DOES have some merit...

Quote:
I agree that coax/BNC are noticably better than optical. That some Sony products are optical only (because they own the format) is ridiculous. Definitely do go coax when you get your new DAC.
And you even back me up here
post #29 of 106
Yes Duncan,

You were correct about that price you specified, found a review where they quoted around the $800 mark for the unit.

BTW It's nice to know that the BNC cable you bought made such a difference,
I know that HI-FI mags etc ALWAYS favour co-ax leads for AV connection etc
over optical so I guess that was a given..

Now I know what my next purchase will be

I will try and hunt down a good quality lead of this type and let you know
how I get on...
post #30 of 106

Will this ever stop?..

Quote:
Originally posted by Dusty Chalk
oversampling == 16/44.1 -> 16/88.2 (2x oversampling), 16/176.4 (4x oversampling), etc.;
upsampling == 16/44.1 -> 24/96, 24/192, etc.
In case anybody is really interested in facts and not in marketing BS:
http://www.madrigal.com/upconversion.htm
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