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Author Topic: Why do Non Oversampling Filterless DAC sound so good  (Read 31372 times)

regal

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Why do Non Oversampling Filterless DAC sound so good
« on: September 10, 2006, 03:42:14 PM »

In the sub $1000 DAC market I don't think a  
non oversampling DAC can be beat.  Reading Mr
Lavry's papers it would seem a filterless DAC
should be terrible without the smoothing of the
filter.   Why do these DAC sound so good?
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crm0922

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #1 on: September 10, 2006, 04:42:08 PM »

Could you name a product that you suggest sounds better because it does not use oversampling?

How about about a toy like this: ?

http://www.diyparadiso.com/dac1.htm

The page author is pretty clear that he doesn't consider this a better solution for accurate 20k BW audio.  

I like when the guy said his wife liked the non-oversampling DAC better because it was "less aggressive".  Try "rolled off" in frequency response.  If one likes that sound, a simple 3rd order filter can easily be added to any DAC without the inadequately attenuated aliasing effects of a non-oversampled DAC.

Your observation is very subjective and gives rise to no useful discussion of the technical nature of the filtering problem in band-limited sampling....which was solved years ago....by oversampling...

If you have a theory as to why such a DAC would be anything but a compromise of the original signal, we're all ears.

Chris
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regal

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Andy Peters

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #3 on: September 10, 2006, 08:23:32 PM »

regal wrote on Sun, 10 September 2006 13:54

http://www.sakurasystems.com/articles/Kusunoki.html


Well, that guy is an idiot.  First of all, I think he confuses oversampled conversion with non-oversampled, and he confuses each type's anti-aliasing requirements.

Non-oversampling Digital filter-less DAC Concept by Ryohei Kusunoki

This 'n' is called the number of taps. The more taps it has, the higher the performance of the filter is supposed to be.


Ummm, not.  The number of taps is chosen to meet the filter design requirements.  Maybe he thinks that having more taps in your filter is like having more cylinders in your car engine?  More cylinders, more horsepower.  Or something like that.

Quote:

  It is rather hard to understand this diagram instinctively. It didn't hit home with me, either.


Perhaps it's because you're a fucking idiot?

Then there's the following, which sorta proves the above conjecture (the part about "fucking idiot"):

Quote:

But, one day, it occur to me to replace it with the equivalent of the reproducing hardware system. (diagram 6). The delay circuit is replaced with that of the delay of speed of sound, the multipliers with the attenuators, and the adding is synthesized in the space. The number of the speakers corresponds to that of taps. The diagram shows, as an example, the computation of CD data through the high-performance digital-filter SM5842. The accompanied numbers are the actual sizes in the space when replaced with the hard-ware. Since the sampling frequency of CD is 44.1kHz, each delay time for the 1 x sampling is 22.ms per tap. To achieve 8 x sampling, SM5842 repeats 2 x sampling three times, and each step incorporates the taps of, 169 degrees for 2 x, 29 degrees for 4 x, and 17 degrees for 8 x. The accumulated delay of each step becomes, 1.92ms, 0.16ms, and 0.05ms: total of 2.13ms.
    Our auditory sense does the frequency analysis at every 2ms interval, and 2.13ms of delay can be caught by our ear.
    If the speed of sound is 346m/s, the total length of the row of speakers becomes 737mm. ( In the diagram, the distance between each speaker is presented by the total delay divided by the total number of taps.)


I mean, jeez: what a maroon.

-a
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danickstr

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #4 on: September 10, 2006, 09:16:58 PM »

Andy Peters wrote on Sun, 10 September 2006 20:23



Perhaps it's because you're a fucking idiot?




Shocked
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Nick Dellos - MCPE  

Food for thought for the future:              http://http://www.kurzweilai.net/" target="_blank">http://www.kurzweilai.net/www.physorg.com

Gunnar Hellquist

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #5 on: September 11, 2006, 12:52:40 PM »

regal wrote on Sun, 10 September 2006 22:54

http://www.sakurasystems.com/articles/Kusunoki.html


Towards the end he says it himself:
So basically this is a disaster : not even something to publish


Regal, I think you are a troll only wanting to make serious people angry. If you want us to take you seriously, you need to come up with some real-world product in the price bracket you mentioned!

Gunnar
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Gunnar Hellquist
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crm0922

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #6 on: September 11, 2006, 12:57:28 PM »

Gunnar Hellquist wrote on Mon, 11 September 2006 12:52

regal wrote on Sun, 10 September 2006 22:54

http://www.sakurasystems.com/articles/Kusunoki.html


Towards the end he says it himself:
So basically this is a disaster : not even something to publish


Regal, I think you are a troll only wanting to make serious people angry. If you want us to take you seriously, you need to come up with some real-world product in the price bracket you mentioned!

Gunnar


Hey Gunnar, I think you are confusing the article I mentioned, which was a guy making a DIY non-oversampling converter just for kicks.  The kusunoki guy seemed to take himself pretty seriously.

Chris
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danlavry

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #7 on: September 11, 2006, 01:12:57 PM »

danickstr wrote on Mon, 11 September 2006 02:16

Andy Peters wrote on Sun, 10 September 2006 20:23



Perhaps it's because you're a fucking idiot?




Shocked


My comments regarding the basics of oversampling can be read in the article on my web:  

http://www.lavryengineering.com/white_papers/sample.pdf

The short of it:
1. The DA anti imaging filter required for elimination of aliased images for say a 44.1KHz CD format is very demanding!
Say you want to achieve only 60dB rejection at 20KHz, and you want to have a 3dB bandwidth at 20KHz (-3dB attenuation at 20KHz). A circuit designer can recognize that you need tons of filter poles, which would lead to about dozens of op amp stages all with precision parts (a lot of 1% caps and resistors and possible hand tweaking ...).

2. Say you have done such a crazy filter (and 60dB is a pretty poor filter to start with), then you have an additional attenuation of about -.7dB due to the sineX/X effect (see my paper at bottom of page 3).

I am not an advocate of huge upsampling ratios, but clearly, some upsampling is in order. As soon as you go X2, much of the filter requirement is gone (roughly 12 times easier job, because the transition range went from about 2KHz to 24KHz). Also, most of the sinX/X problem is gone, or is at least "easily correctable".

Anyone that uses a non over sampling DA, and thinks it sounds good are saying 2 things:

1. They like the upper band to be attenuated significantly, and they like the associated phase shift that comes with it (all the way down to 10KHz...)
2. They can stomach aliasing, especially into the higher frequencies.

I do not intend to argue likes or dislikes. But if the intent od a DA is anywhere near converting digital to analog with minimum of distortions, the upsampling DA is inherently a better way to go. And let us no forget that aliasing distortions are not harmonic, thus very non musical.

My best guess is that one can "stand it" if they filter out the higher band. One can use a very high order EQ (which will also cause undesirable phase non linearity).

Regards
Dan Lavry
http://www.lavryengineering.com
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regal

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #8 on: September 14, 2006, 11:52:20 PM »

The good thing about these DAC's is not the non-oversampling its the lack of a filter.  Your ears and drivers function as the filter.

 These DAC's have become very popular in the DIY community and I thought it interesting that there had been no mention of them at all on this board.  I find Lavry's reply informative but he dodged the main benefit.   If one were to build the
ultimate theoretical DAC,  it would have no filter andd the DIY community has basically discovered that a filter isn't needed.

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Andy Peters

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #9 on: September 15, 2006, 02:06:09 AM »

regal wrote on Thu, 14 September 2006 20:52

The good thing about these DAC's (sic) is not the non-oversampling its (sic) the lack of a filter.  Your ears and drivers function as the filter.


Oh, great--variable filters.  And this doesn't even make any sense if you understand the theoretical reason the reconstruction filter.

Quote:

These DAC's (sic) have become very popular in the DIY community and I thought it interesting that there had been no mention of them at all on this board.


No mention because the idea is ridiculous?

Quote:

 I find Lavry's reply informative but he dodged the main benefit.   If one were to build the ultimate theoretical DAC,  it would have no filter andd the DIY community has basically discovered that a filter isn't needed.


He has not dodged the "main benefit."  He's demonstrated clearly and succinctly why filtering is necessary while also pointing out how oversampling mitigates certain practical problems one must deal with when implementing filters.

Clearly, then, the DIY community (or, at least the small subsection of that community that believes the sort of hooey you advocate) is basically (wait for it ...) a bunch of idiots who have things completely backwards.

If one were to build the "ultimate theoretical DAC," it would have the ultimate theoretical reconstruction filter.

-a
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crm0922

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #10 on: September 15, 2006, 07:33:20 AM »

regal wrote on Thu, 14 September 2006 23:52

The good thing about these DAC's is not the non-oversampling its the lack of a filter.  Your ears and drivers function as the filter.

 These DAC's have become very popular in the DIY community and I thought it interesting that there had been no mention of them at all on this board.  I find Lavry's reply informative but he dodged the main benefit.   If one were to build the
ultimate theoretical DAC,  it would have no filter andd the DIY community has basically discovered that a filter isn't needed.




Everything in this post is wrong.

Chris
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chrissugar

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #11 on: September 15, 2006, 10:05:58 AM »

Last week I listened with some friends to two non oversampling DACs. The unanimous conclusion was that they sound awful. They couldn't even equal the internal conversion of a Marantz CD6000KI's, which is a mediocre one. Never heard one non oversampling DAC that sounded good (right).
And compared to the Lavry DA10 the difference is night and day.

And by the way, in another comparison, the DA10 with some audiophile 24bit/96K records (read minimalist, 2 microphone,  high resolution orchestral recordings) sounded significantly better then this 15000$ high end audiophile preamp/DAC:
http://www.boulderamp.com/owners_manuals/1012_Owners_Manual. pdf
review here:
http://www.stereophile.com/amplificationreviews/505/index.ht ml

chrissugar
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danlavry

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #12 on: September 15, 2006, 02:16:52 PM »

regal wrote on Fri, 15 September 2006 04:52

The good thing about these DAC's is not the non-oversampling its the lack of a filter.  Your ears and drivers function as the filter.

 These DAC's have become very popular in the DIY community and I thought it interesting that there had been no mention of them at all on this board.  I find Lavry's reply informative but he dodged the main benefit.   If one were to build the
ultimate theoretical DAC,  it would have no filter andd the DIY community has basically discovered that a filter isn't needed.




A DA without a filter introduces image energy that is nearly as high as the energy in the audible range. In the case of non up-sampling DA, the audio content is centered at the sample rate, twice the sample rate, 3 times…. And it goes up to very high frequencies. The amplitude decay curve is rather slow…

Assuming that you could not hear above 22KHz, you say that the image energy will not be heard. But in fact, the DA output signal, both the audio and the images at frequencies above audio must go through some electronics before reaching your ears. Such electronics may be a preamp, a power amp, a speaker, a headphone amp and a headphone… or in a music production environment the signal may be sent to an analog mixer…

It is one thing to ask an amp, or a speaker (or whatever gear is there) to “process” a signal with energy content that is limited to 20Hz-20KHz (or say 10Hz-50KHz) accurately. It is another thing to expect accurate results when the signal contains relatively high energy at high frequencies. When you try to do that, you will find out that the image energy interferes with the electronics in many way. It degrades the transfer curve, which causes inter modulation at all frequencies including the audible ones, it can ruins circuit badly.

If you did not understand what I said, here is another view, perhaps more intuitive:  The DA output signal BEFORE the filter is typically (depending on the signal) made out of a very fast steps, and for some signals, the step amplitude is high (think of say sampling a 10KHz full scale sine wave). Fast changes are made of high frequencies. The electronics after the DA would have a “difficult time” tracking those “fast steps”. An anti imaging filter will “smooth out” the signal so that the signal will move much slower, and without the sudden “jerky” steps. Such a signal happened to represent the original waveform before it ever hit the first microphone…  

Then comes the other point: a DA with no up sampling has very non flat amplitude vs. frequency response. In theory, a DA is perfect, because the samples are “zero width”, each sample with proper amplitude. But in practice, zero width samples, or very narrow pulses, carry very little energy, so the outcome will be very weak. A weak signal calls for a lot of amplification, which raises the noise, and that is undesirable.

So instead of narrow pulses, we go for a “stair case” waveform, where each value is held steady until the next sample.  That practice (we call it NRZ for “not return to zero). We do so instead of the theoretical narrow pulses (we call them RZ because with a narrow pulse the signal between samples is zero most of the time).

Now, doing NRZ (stair case) solves the noise problem, but it brings on another problem – it causes some attenuation when you get to higher audio frequencies – nearly a dB at 20KHz if I recall (see my paper on Sampling, Over sampling, Aliasing, imaging).  That roll off curve (sinX/X shape) is NOT something you can fix with an analog EQ (poles and zeros). When you up sample, that problem goes away. See the graph in the paper I recommended.

I could say much more, but those reasons are more then enough to explain that non up sampling has problems, and why no filter is bad news.

Regards
Dan Lavry
http://www.lavryengineering.com
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zetterstroem

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #13 on: September 23, 2006, 02:15:42 PM »

(although i noone here really cares and are totallly focused on theory....)

i own an audionote dac that has only 18dB/oct analog lowpass filters..... and it sounds far better than EVERYTHING i've heard..... (i haven't heard dan's stuff yet  Crying or Very Sad ) the top end is sooooo smooth and i don't hear anything resembling aliasing...... the sound is more transparent and open than eg. benchmark etc.

so to say that the entire diy community is wrong is very narrowminded......

i think the simplest explanation for the second to none sound is less crap in the signal path.... plain and simple.....

anyway,....
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Jon Hodgson

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #14 on: September 23, 2006, 02:49:53 PM »

zetterstroem wrote on Sat, 23 September 2006 19:15

(although i noone here really cares and are totallly focused on theory....)

i own an audionote dac that has only 18dB/oct analog lowpass filters..... and it sounds far better than EVERYTHING i've heard..... (i haven't heard dan's stuff yet  Crying or Very Sad ) the top end is sooooo smooth and i don't hear anything resembling aliasing...... the sound is more transparent and open than eg. benchmark etc.



Ok firstly your first comment is incorrect and actually a little offensive. Dan, myself and others here DO care very much about practice, but we care about finding out what is REALLY going on, not about vague and often incorrect theories and explanations for what people hear or sometimes only think or claim they hear.

Now in response to your second paragraph.

Firstly Dan's response was about DACs with no filters whatsoever, not just no oversampling.
Secondly it is not surprising that you hear no aliasing, assuming that you are playing back at 44.1kHz or above, any aliased components would be above what you can hear anyway. The point of the reconstruction filter is not to eliminate components that you can hear directly, but rather to eliminate components which MIGHT cause problems further down the signal path which you could hear.
Thirdly saying that the sound is "more transparent and open" does not help us to know what is going on, until we can define what differences in the signal make it sound "more transparent and open" to you. Is it a more accurate signal, or is it actually a less accurate one? And whatever the answer to that might be, is it a result of the choice of filter versus the benchmark?

So your personal experience is interesting in itself, but it isn't enough to support the hypothesis that having no oversampling is in any way superior.
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crm0922

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #15 on: September 25, 2006, 10:35:30 AM »

zetterstroem wrote on Sat, 23 September 2006 14:15

(although i noone here really cares and are totallly focused on theory....)

i own an audionote dac that has only 18dB/oct analog lowpass filters..... and it sounds far better than EVERYTHING i've heard..... (i haven't heard dan's stuff yet  Crying or Very Sad ) the top end is sooooo smooth and i don't hear anything resembling aliasing...... the sound is more transparent and open than eg. benchmark etc.

so to say that the entire diy community is wrong is very narrowminded......

i think the simplest explanation for the second to none sound is less crap in the signal path.... plain and simple.....

anyway,....


Please check your system for proper frequency response from 20Hz to 20kHz.  It should measure +/- 0.5db at all frequencies to be in the realm of a faithful reproduction of the source signal.

Chris
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danlavry

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Re: Why do Non Oversampling Filterless DAC sound so good
« Reply #16 on: September 25, 2006, 04:33:32 PM »

zetterstroem wrote on Sat, 23 September 2006 19:15

(although i noone here really cares and are totallly focused on theory....)

i own an audionote dac that has only 18dB/oct analog lowpass filters..... and it sounds far better than EVERYTHING i've heard..... (i haven't heard dan's stuff yet  Crying or Very Sad ) the top end is sooooo smooth and i don't hear anything resembling aliasing...... the sound is more transparent and open than eg. benchmark etc.

so to say that the entire diy community is wrong is very narrowminded......

i think the simplest explanation for the second to none sound is less crap in the signal path.... plain and simple.....

anyway,....


Please read the rules of the forum. We do NOT talk here about individuals opinions of what sounds good. There are many places where people can argue what sounds good to them. This forum may be about issues you do not care about, but others do.

I do not know what "diy community" stands for. Is it "Do it yourself"?

Dan Lavry
http://www.lavryengineering.com  
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