DSD: Explain it to me because I'm not getting it

[sdolezalek]

Interesting post by the folks at iFi regarding filtering and their upcoming iFi iDSD Pro series (posted at: iFi Audio "Mini" desktop line discussion thread - Page 27 :

 

Why filter the signal at all?

 

First, we must understand that a DAC-Chip will produce substantial supra-sonic output (which we justly may call “digital distortion”) in addition to the Audio signal we want. Just how this looks like depends on many factors. Rather than looking all options, let's focus on the BB DSD chip we use in iFi products.

 

It has a core that runs normally at a speed of around 11.3MHz to 12.3MHz. This is a very high speed. This is the speed at which the elements in the core switch. As the process is switching, it creates higher frequency components reaching much higher than main switching frequency.

 

This switching is one of the processes that produces this noise outside the audio band, the others are related to sample theory and produces what is often called “images”. Simply said, the actual audio signal is “mirrored” around the sample rate in a frequency plot, hence the name mirror images.

 

 

 

Source: http://

 

Most audio circuitry cannot handle such supra-sonic signals, they are too fast and cause distortion to our audio signal. So what we require with any DAC is a filter that so to speak “strains out” the unwanted noise and leaves the audio signal. And ideally it gets all the noise and leaves the audio totally untouched.

 

In the real world ideal filters do not exist. A filter that removes the supra-sonic noise will have impact on the audio range and will introduce either phase-response variation, transient-response variation or both.

 

 

 

 

Source: http://www.electronics-tutorials.ws/filter/fil82.gif

 

We have to sail between the Scylla of insufficient filter selectivity (too much noise gets through) and the Charybdis of excessive filter impact on the audio (we filter out most noise and pad a lot of distortion the music). But filter to some degree we must, so we must chart a course that will hopefully take through instead being wrecked on rocks of Charybdis or sucked into the chaotic whirlpool of the Scylla.

[Miska]

It has a core that runs normally at a speed of around 11.3MHz to 12.3MHz. This is a very high speed. This is the speed at which the elements in the core switch. As the process is switching, it creates higher frequency components reaching much higher than main switching frequency.

 

This switching is one of the processes that produces this noise outside the audio band, the others are related to sample theory and produces what is often called “images”. Simply said, the actual audio signal is “mirrored” around the sample rate in a frequency plot, hence the name mirror images.

 

 

 

Source: http://[ATTACH=CONFIG]16968[/ATTACH]

 

What they forgot to tell here is that only delta-sigma part of the DAC chip operates at those frequencies. Not the "ladder" part when you run it in PCM mode.

 

What they also forgot to tell is that due to SAH/ZOH oversampling in PCM mode, the images appear at multiples of 352.8 kHz for 44.1-base input rates and at multiples of 384 kHz for 48-base input rates.

 

As you can see from this iFi iDSD Micro measurement result:

 

 

So when you do proper oversampling and delta-sigma modulation externally and run the DAC in DSD mode, you get rid of those images altogether:

[Hiro]

What they forgot to tell here is that only delta-sigma part of the DAC chip operates at those frequencies. Not the "ladder" part when you run it in PCM mode.

 

What they also forgot to tell is that due to SAH/ZOH oversampling in PCM mode, the images appear at multiples of 352.8 kHz for 44.1-base input rates and at multiples of 384 kHz for 48-base input rates.

 

As you can see from this iFi iDSD Micro measurement result:

[ATTACH=CONFIG]16973[/ATTACH]

 

 

So when you do proper oversampling and delta-sigma modulation externally and run the DAC in DSD mode, you get rid of those images altogether:

[ATTACH=CONFIG]16974[/ATTACH]

 

I wish more manufacturers would enable direct access to their delta-sigma modulators (at their top sampling rates) as iFi Audio does it with their iDSD DACs!

[Paul R]

I wish more manufacturers would enable direct access to their delta-sigma modulators (at their top sampling rates) as iFi Audio does it with their iDSD DACs!

 

Oh, they will. As soon as they have played the PCM only market for all it is worth, every top DAC maker who has not already embraced DSD will go that way, selling upgrades.

 

Almost all the objections I hear are traceable back to not having realized a great enough return from the current, often uber expensive DACs. Not true of all, but true in some highly visible cases, often those with great snob appeal.

 

TINAR, IMO, YMMV, etc.

[davide256]

Most of the issue with DSD is paucity of natively recorded DSD with decent engineering. Get some good native DSD recordings like the San Francisco Symphony

recordings. Like Sheffield Direct to Disc LP's they will shine through on even modest DSD DAC's. SACD rips are very hit or miss for quality.

[bmoura]

Most of the issue with DSD is paucity of natively recorded DSD with decent engineering. Get some good native DSD recordings like the San Francisco Symphony

recordings. Like Sheffield Direct to Disc LP's they will shine through on even modest DSD DAC's. SACD rips are very hit or miss for quality.

 

Yes there are 4 SF Symphony recordings that were done in DSD by Gus Skinas and Dawn Frank. The others were likely recorded in PCM.

 

As far as native DSD downloads, there are literally hundreds of them on the Native DSD and Pentatone web sites. Lots to choose from there.

[craighartley]

Yes there are 4 SF Symphony recordings that were done in DSD by Gus Skinas and Dawn Frank. The others were likely recorded in PCM.

 

As far as native DSD downloads, there are literally hundreds of them on the Native DSD and Pentatone web sites. Lots to choose from there.

 

According to the provenance information on the sanfranciscosymphony.downloads.net site, nine of the eleven Mahler albums were recorded in DSD (the 8th symphony and the Songs with Orchestra albums were recorded in pcm).

 

Do you have evidence to the contrary?

[bmoura]

According to the provenance information on the sanfranciscosymphony.downloads.net site, nine of the eleven Mahler albums were recorded in DSD (the 8th symphony and the Songs with Orchestra albums were recorded in pcm).

 

Do you have evidence to the contrary?

 

Four of the Mahler symphonies were recorded by the Super Audio Center staff in DSD. Those are not in question. As to the other 7, I have heard conflicting accounts as to whether they were recorded in DSD or PCM.

[cookiemarenco]

Four of the Mahler symphonies were recorded by the Super Audio Center staff in DSD. Those are not in question. As to the other 7, I have heard conflicting accounts as to whether they were recorded in DSD or PCM.

 

Getting information about the format a project was originally recorded in is very difficult. Before we release a recording, we spend dozens of hours communicating with engineers, owners of masters and anyone who can verify what actually happened at a session. It's not easy to get answers, but we've been successful with the SF Symphony and we feel we have accurate information based on corroboration of information.

 

In the case of the San Francisco Symphony, we have done extensive research directly with the San Francisco Symphony administration, Jack Vad -- their chief recording engineer, Gus Skinas and other engineers involved directly with the recording. We have verification in writing as to how each symphony was recorded.

 

You'll find the provenance (the source recording and history) on each of the MicroStores for the albums at Downloads NOW! Scroll down the list to San Francisco Symphony, click on the project in question and at the top of the page you'll find the Provenance.

Downloads NOW!

 

Enjoy!

Cookie Marenco

Blue Coast Music Group

[firedog]

Four of the Mahler symphonies were recorded by the Super Audio Center staff in DSD. Those are not in question. As to the other 7, I have heard conflicting accounts as to whether they were recorded in DSD or PCM.

 

I think if you go to the Blue Coast site and look up the Symphonies, you will find reliable provenance info.

 

edit: Cookie beat me to the punch!

[Hiro]

Oh, they will. As soon as they have played the PCM only market for all it is worth, every top DAC maker who has not already embraced DSD will go that way, selling upgrades.

 

Almost all the objections I hear are traceable back to not having realized a great enough return from the current, often uber expensive DACs. Not true of all, but true in some highly visible cases, often those with great snob appeal.

 

TINAR, IMO, YMMV, etc.

 

Today, when even an average smartphone has more computational power than any DAC chip, it just doesn't make sense to make the PCM>SDM conversion inside the DAC chip any more. All delta sigma DACs should come with direct sigma delta inputs IMO.

[rickca]

Oh, they will. As soon as they have played the PCM only market for all it is worth, every top DAC maker who has not already embraced DSD will go that way, selling upgrades.

 

Almost all the objections I hear are traceable back to not having realized a great enough return from the current, often uber expensive DACs. Not true of all, but true in some highly visible cases, often those with great snob appeal.

 

There's a lot more to the design and implementation of expensive DAC's than the decision about whether to directly support DSD.

[Paul R]

There's a lot more to the design and implementation of expensive DAC's than the decision about whether to directly support DSD.

 

Actually, without being ornery or mean, or even insulting, you are correct. There is a great deal more. But nothing on the planet justifies a $40K DAC, much less a $150K DAC. *Nothing*

 

Now if you have the cash and want to buy one, more power to you. But it is not and will not be better than the $2500-$6000 DAC out there, which represents about as good as a DAC can physically be, given today's technology.

 

And *those* DACs, while better than a $500 DAC, are not "night and day" better - not any where near as impactful on a system as the speakers are. Spending an extra $2K on speakers rather than a DAC can make an enormous difference in a system.

 

And, DSD is a far less expensive way to get the same kind of audio quality, or better, than the best of the PCM only DACs.

[alfe]

Actually, without being ornery or mean, or even insulting, you are correct. There is a great deal more. But nothing on the planet justifies a $40K DAC, much less a $150K DAC. *Nothing*

 

Now if you have the cash and want to buy one, more power to you. But it is not and will not be better than the $2500-$6000 DAC out there, which represents about as good as a DAC can physically be, given today's technology.

 

And *those* DACs, while better than a $500 DAC, are not "night and day" better - not any where near as impactful on a system as the speakers are. Spending an extra $2K on speakers rather than a DAC can make an enormous difference in a system.

 

And, DSD is a far less expensive way to get the same kind of audio quality, or better, than the best of the PCM only DACs.

 

I'm sure you had the chance to compare

[Paul R]

I'm sure you had the chance to compare

 

 

Wow - snarky aren't we?

 

Actually, yeah, I have heard a few of them. The one I want to get ears on is the new PS DAC. The DaVinci I have not heard at home, but it didn't impress me in the two listening rooms I have heard it in. The company impresses me even less.

 

AMR sounds great, but - those darn tubes! dCS - they are the screaming edge, and I am not at all sure they are worth the extraordinary cost. Now if I could get em at 50% off...

 

Wavelengths - Crimson, hell yeah, that one is worth the money. But realize there you are paying for one man's attention to detail, and even then, it doesn't range up there with the cost of the DaVinci- though it sounds every bit as good or better. Despite the darn tubes.

 

And again, the DSD DACs seem to be producing sound right up there in the top of line range. It takes a LOT more work to get great sound out of PCM than it does to get the same sound out of a DSD DAC.

-Paul

[alfe]

Wow - snarky aren't we?

 

-Paul

 

If you start your comment with IMFNHO I will not be snarky anymore

[Paul R]

If you start your comment with IMFNHO I will not be snarky anymore

 

 

Sorry- doesn't make it opinion just because someone else does not want it to be true. But nobody says you have to agree with it either. Perfectly welcome to your own version of the truth.

[Daudio]

Over the years I have never understood statements like this. It is as if mankind development of ears has resulted in different hearing capacities (not withstanding adverse medical conditions). The sound coming from an audio system is the same regardless of who is listening to it. It is either there are it isn't there.

 

Yes, Bill, it is the same sound, but different ears, different training and experiences. You could look at a famous painting and 'see' it, but someone trained in art history and restoration is obviously going to 'see' a lot more then you, or I, ever will in that same couple of square feet of colors !

 

It is not the motion of the air, or the shape of the pinna, but what is behind the ears, in the brain, that underlies the sensitivity and even 'taste', for audio sound quality. Not mankind, but individual men and women, developing their hearing skills towards different goals and to different degrees.

 

Get it ?

 

 

P.S. Opps, missed a whole page of later posts in my haste to post a reply

[bmoura]

It takes a LOT more work to get great sound out of PCM than it does to get the same sound out of a DSD DAC.

-Paul

 

Very true. Look at most of the Lampizator DACs. Their DSD playback doesn't even require a DAC chip! They simply filter the DSD signal.

 

And the results are quite good - their DSD DAC sounds better to my ears than PS Audio's Directstream and several other DACs costing quite a bit more.

[Hanuman22]

Very true. Look at most of the Lampizator DACs. Their DSD playback doesn't even require a DAC chip! They simply filter the DSD signal.

 

And the results are quite good - their DSD DAC sounds better to my ears than PS Audio's Directstream and several other DACs costing quite a bit more.

 

bmoura, With about 400 hours on a PS DSD+PikesPeak I'm finding the weak links in the chain widely affect SQ. ie: #1 the USB cable, priority. #2 the power cable, surprisingly affects the upper mid sparkle and warmth. #3 Interconnects, in that order, but upgrading all three variables have drastically affected the PS DSD SQ to the positive. Still working on the IC's.

[AudioDoctor]

I guess I missed the memo that said I need to buy a hot rod computer and convert DSD into PCM or PCM to DSD to play it back on my DAC that plays both...

 

But I do see how someone could be confused by reading this site. No one gives simple answers here, this thread is proof. SO the takeaway from this is that no, you don't need to buy a hot rod of a computer to convert files into other files for playback on a DAC, unless you want to, then by all means, go ahead...

[Jud]

I guess I missed the memo that said I need to buy a hot rod computer and convert DSD into PCM or PCM to DSD to play it back on my DAC that plays both...

 

But I do see how someone could be confused by reading this site. No one gives simple answers here, this thread is proof. SO the takeaway from this is that no, you don't need to buy a hot rod of a computer to convert files into other files for playback on a DAC, unless you want to, then by all means, go ahead...

 

I do all conversions in my non hot rod 7 year old laptop.

[AudioDoctor]

I do all conversions in my non hot rod 7 year old laptop.

 

I dont do any conversions, I play everything natively. Does that make me a heretic?

[Jud]

I dont do any conversions, I play everything natively. Does that make me a heretic?

 

Quick answer: Sure, heretics are sexy!

 

Slow answer: Of course you're converting everything, just in a DAC chip instead of a computer.

[ted_b]

I guess I missed the memo that said I need to buy a hot rod computer and convert DSD into PCM or PCM to DSD to play it back on my DAC that plays both...

 

But I do see how someone could be confused by reading this site. No one gives simple answers here, this thread is proof. SO the takeaway from this is that no, you don't need to buy a hot rod of a computer to convert files into other files for playback on a DAC, unless you want to, then by all means, go ahead...

 

In any hobby that is in its infancy, with lots of new discovery and discussion, there may be no simple answers. Yes, there are ways to simplify ones audio signal path (like NAS to ethernet renderer to DAC, leaving all general use computers behind) but that doesn't mean there aren't options or others ways that folks have discovered may improve said path! Don't expect simple answers to questions like "what is the best way to..." cuz this is computer audio in its infancy, and lots and lots of options currently exist. There is no one best way (yet) . Doesn't mean you have to get caught up in them.

 

My advice for new folks: realize that there are many ways to skin the cat right now. Find your budget, buy a DAC and a music playback source (pc, renderer, Mac, etc) that you can afford, and then find the sweetspot of that DAC (sample or bit rate where it seems to play music best for your ears). Simply then upsample or downsample your music to that spot for now. Enjoy music, read a little more about options, but continue to enjoy music. Stop reading if it bothers you that there are other newer or better options out there that you can't afford (the time and/or the money). The "hot rod" comments come from hobbyists. If this is not a hobby you want to invest that much time in, then simply enjoy the music.

 

Don't condemn this site for not having easy answers. Some very easy and cost-effective answers are here (it's why, for example, I put the video tutorials together for using JRiver with hirez PCM and DSD). It's daunting at first blush, but only if you want to use all the bells and whistles. So do a little searching. Of course you'll find the folks that like to rip out the engine and put in a new one (sometimes that's me, even). It's a hobby site, too!