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Author Topic: PCM vs. DSD  (Read 1373 times)

Spike1000

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PCM vs. DSD
« on: August 09, 2018, 02:21:20 am »

Biggest of which is cut down of that nasty 'digital' distortion which PCM will create in the analog conversion stage of the DAC. This is a fundamental problem of PCM and no engineering way around it.

Could you elaborate what you mean by this and why it's a problem to you? I'm curious.
Spike

felix2

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Re: PCM vs. DSD
« Reply #1 on: August 09, 2018, 09:55:31 pm »

Could you elaborate what you mean by this and why it's a problem to you? I'm curious.
Spike
Hi Spike. When the CD was invented long ago its promise of 'digital perfection' failed to deliver. Discriminating people clearly hear a strange, unnatural distortion from the best CDs produced of the era - called it the 'digital sound'. But for a long time engineers couldn't figure out what exactly is responsible for the imperfection of the CD. Many solutions were tried but all failed. Then Sony introduced the SACD and right away the sound astound when played with professional equipment of the time. Most of the unnaturalness of CD was gone. Confirmed time again when same songs of CD/SACD compared in blind tests. Another decade passed but still no correct technical understanding.

Then in a landmark science/engineering paper a researcher discovered the reason. It's PCM (pulse code modulation) behind all digital recordings. But, here's the shocker, the recording is not responsible - the playback is. So much effort was spent on improving the recording and they have been chasing the wrong fish. Specifically, the most common type of design of the electronics that actually do the digital-to-analog conversion creates a form of tricky digital error. DSD uses an entirely different kinds of design which has no such errors (but not that it is perfect). This explains why CDs for a long time just sound unnatural.

Today the best DAC equipment recognize the discovery and use better design in the conversion stage and thus sounds much better with PCM signals. But the perfect PCM conversion stage require very expensive design (so-called R-2R ladder network but there are other elements). Go search for DAC with R-R2 design.

For me there is a cheaper solution that more than meet halfway to the R-2R solution. And that is simply convert PCM files to DSD and have the DAC process sound in DSD mode, eliminating PCM altogether. But note only audiophiles care for such thing because nobody who are satisfied with cellphone output give a darn. :)
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pschelbert

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Re: PCM vs. DSD
« Reply #2 on: August 10, 2018, 01:15:03 am »

Hi

there is no serious paper (scientific double blind test) which proves that.

R2R DAC are lower precision than sigma-delta which are today the top notch. See chip manufacturers datasheets.

I know its an old claim in the HiFi industry, never could be proven (as far as I know, may be somebody knows a serious AES paper which I am not aware of).

My experience is that 96/24Bit PCM is the uppermost reasonable format.

I never experienced a quality improvement converting CD to other highres format whatever I tried.
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michael123

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Re: PCM vs. DSD
« Reply #3 on: August 10, 2018, 03:16:42 am »

It is about sound my friend. Sound.

Not specs, digits and AES papers :)
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pschelbert

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Re: PCM vs. DSD
« Reply #4 on: August 10, 2018, 03:27:09 am »

yes, its about sound not myths.

Professionals have more possibilities to do neutral tests compared to consumers and to publish their results.
That's the reason papers are a way to learn more.
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dtc

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Re: PCM vs. DSD
« Reply #5 on: August 10, 2018, 08:44:35 am »

Harshness and digital glare have been part of digital audio for years. All you have to do is listen to a good record (aka vinyl) played through a tube system and you recognize the characteristics of the two different approaches.   In many case, the ultimate goal of digital design is to get to the liquidity of an all analog system.  For others, an all analog system is perceived as mushy, without the details some people want. You say "tomato", I say "tomato" -  never did know how to write that out.

For CDs, digital glare is often associated with the brick wall filter typically implemented at 22.05 KHz (44.1Khz/2). This eliminates the high frequency noise at the Nyquist frequency which comes from the D to A conversion. This filter also causes artifacts in the normal hearing range. Higher sample rates moved the filter to a much higher frequency and allowed for it to be much less steep. This moved the artifacts out of the normal hearing range. That is one of the reasons that DAC designers went to oversampling in their DACs.  Most modern DACs do oversampling, although there are a small number of NOS (non-oversampling) DACs out there.  High res files were originally designed to help overcome the brick wall filter effects, but with most DACs doing upsampling, that aspect of high res files is less important.

R-2R DACs are a very simple D to A converters, but they do require quite precise resistance values.  And, the real magic usually comes not in the ladder, but in the filters that are applied after the ladder conversion. The same is true for DSD conversions. The filters are a key to the final sound.

MSB has been a leader in high end audio for many years. The link below is a description of their R-2R ladder DAC implementation. Obviously, this is a manufacturer hyping its technology, but they clearly believe in their approach and MSB DACs are highly regarded in the industry.

http://www.msbtechnology.com/faq/why-ladder-dacs/

DSD does not require the same detailed mathematically conversion that PCM does. It is therefore often viewed as being simpler and more accurate, without any of the artifacts associated with brick wall filters.

Modern DACs, both PCM and DSD, often implement multiple filters that the user can select based on their own hearing. This is an acknowledgement that no D to A process is entirely accurate and that, even if it were, people hear differently.

The interesting thing to me is the emphasis DAC manufacturers and software designers are spending on filter design.  Many openly market their filter design and many provide multiple options.  The hardware design is still important but their is a current emphasis on software, in the form of filter design, for both PCM and DSD.

With all that said, lets not forget that the main purpose for most people is simply to get music that sounds good to them. And we all hear differently.
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kr4

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Re: PCM vs. DSD
« Reply #6 on: August 10, 2018, 09:11:57 am »

 Tomayto, tomahto.
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Kal Rubinson
"Music in the Round"
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Screwdriver

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Re: PCM vs. DSD
« Reply #7 on: August 10, 2018, 09:23:53 am »

It's all about how the music was engineered and mastered. PCM, DSD does not matter to me, but am glad that MC has the option.

I have been testing this for my own entertainment in JRiver, Audirvana and HQPlayer. I have converted PCM to DSD on the fly up to DSD512. Used SACD ISO's, DSF etc. I have taken DSD's and re-sampled to PCM. DAC's I used that I own or that I got on loan from my local hi-fi shop and friends. Chord Qutest, Schiit BiFrost MB, Topping D50 and Starting Point Systems DAC3.

(Just my opinion), but it all came down to the quality of the original file. A nice engineered 24/88.2 FLAC can sound way better than a poorly mastered SACD. A 16/44 sounds identical to me when re-sampled at PCM512. I will say that the Native DSD files I got from Blue Coast Records sounded amazing, but that goes back to my how they were engineered argument.
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dtc

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Re: PCM vs. DSD
« Reply #8 on: August 10, 2018, 09:58:32 am »

Thanks Kal. A long time problem solved  :)
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