dsd DSD Offshoot Discussion From MQA Topic

[Shadders]

Hi,

Another document, earlier from 1997 from Sony/Philips :

 

http://www.superaudiocenter.com/images/dsd.pdf

 

Indicates "Because the instantaneous amplitude of the analog waveform is represented by the density of pulses, the method is sometimes called Pulse Density Modulation (PDM)"

 

The use of the word "sometimes" may mean the document is not strictly accurate.

 

Regards,

Shadders.

[jabbr]

1 hour ago, Miska said:

 

2-bit PCM, 1-bit PCM, 4096-bit PCM. Or even 0-bit PCM. To me that is different than 0-level SDM or 4096-level SDM.

 

P.S. You can ask HQPlayer to create you 1-bit PCM if you want by editing config file manually and set "dac_bits" to "1". And it will give you that. But that won't give you DSD.

 

 

What does the bitstream of 1 bit PCM look like, and assuming it puts out music, how dies that differ from DSD?

[Miska]

1 minute ago, Shadders said:

Indicates "Because the instantaneous amplitude of the analog waveform is represented by the density of pulses, the method is sometimes called Pulse Density Modulation (PDM)"

 

You can consider it as PDM or PWM. Only distinction is how you interpret the stream.

[Miska]

26 minutes ago, jabbr said:

What does the bitstream of 1 bit PCM look like, and assuming it puts out music, how dies that differ from DSD?

 

https://www.sonarnerd.net/tmp/sweep2-1.zip

 

Just one example of course.

[crenca]

7 minutes ago, Miska said:

 

https://www.sonarnerd.net/tmp/sweep2-1.zip

 

Just one example of course.

 

What's in this file?  How does it differ from DSD?

[Miska]

2 minutes ago, crenca said:

What's in this file?  How does it differ from DSD?

 

It is a WAV file with frequency sweep, just one bit active. But it is MSB-aligned so you can easily listen to it.

 

It has not gone through Sigma-Delta (or Delta-Sigma, what ever, it is a loop anyway) modulator.

 

[crenca]

1 minute ago, Miska said:

 

It is a WAV file with frequency sweep, just one bit active. But it is MSB-aligned so you can easily listen to it.

 

It has not gone through Sigma-Delta (or Delta-Sigma, what ever, it is a loop anyway) modulator.

 

 

Ok, how does it answer jabbr's question:

 

"What does the bitstream of 1 bit PCM look like, and assuming it puts out music, how dies that differ from DSD?"

[Miska]

11 minutes ago, crenca said:

Ok, how does it answer jabbr's question:

 

"What does the bitstream of 1 bit PCM look like, and assuming it puts out music, how dies that differ from DSD?"

 

I think it clearly answers it by giving an example how it looks like and it is listenable too.

 

The difference is that one has the S-D modulator, the other one doesn't. DSD is 2-level SDM.

 

[Jud]

5 minutes ago, Miska said:

 

I think it clearly answers it by giving an example how it looks like and it is listenable too.

 

The difference is that one has the S-D modulator, the other one doesn't. DSD is 2-level SDM.

 

 

OK, now multi-bit SDM: Is it PDM/PWM, PCM, or something else (sui generis SDM?)?

[Miska]

13 minutes ago, Jud said:

OK, now multi-bit SDM: Is it PDM/PWM, PCM, or something else (sui generis SDM?)?

 

You can put it under same category, but I'd rather talk about "SDM" for clarity. It is just like PDM or PWM, but pulses can have more than two levels. You could have three levels where the pulse can also stop at the middle. Or five levels which is typical multi-level SDM where you have pulses of for example following levels: -5, -2.5, 0, +2.5, +5 V. Each pulse can have varying width. It is also all the time furiously using the entire range, regardless of signal amplitude.

 

[Jud]

12 minutes ago, Miska said:

 

You can put it under same category, but I'd rather talk about "SDM" for clarity. It is just like PDM or PWM, but pulses can have more than two levels. You could have three levels where the pulse can also stop at the middle. Or five levels which is typical multi-level SDM where you have pulses of for example following levels: -5, -2.5, 0, +2.5, +5 V. Each pulse can have varying width. It is also all the time furiously using the entire range, regardless of signal amplitude.

 

So for you is SDM a necessary part of producing current commercial PDM/PWM, or are there other commonly used methods?

[fas42]

For real world uses of PWM, this is a very folksy chat about the process ...

 

 

[Miska]

43 minutes ago, Jud said:

So for you is SDM a necessary part of producing current commercial PDM/PWM, or are there other commonly used methods?

 

You can also produce PWM using analog modulator, like for example in Hypex amplifier modules (and most class-D). It doesn't necessarily require digital process.

 

[Miska]

It is explained in a quite decent way in Wikipedia PWM article, both the analog modulation with sawtooth and comparator, and the digital SDM method.

https://en.wikipedia.org/wiki/Pulse-width_modulation

 

[jabbr]

20 hours ago, Paul R said:

 

That's kind of like saying that life is just a series of chemical reactions. It may be a bit over simplified. How you do something is often quite important, perhaps this is one of those cases. 

 

Oohhh metaphysics!

 

That question is definitely beyond my pay grade. 

 

20 hours ago, Paul R said:

 

I will leave it as an exercise for you to figure out the ramifications of that. There are a few.

 

-Paul 

 

 

I hope the differences between PCM and DSD can be answered by math/physics and don’t need to invoke a higher power ( @Miska? 😂)

 

I’ve been playing Devil’s advocate here of course and really having great fun watching @mansr arguing one point with one hand and at the same time arguing against me, even when I’m siding with him on the other side of your argument. I’ve been wondering if he will simply cease to exist due to an internal logical inconsistency ( @Miska this is a joke in case you are wondering! 😂😂😂)

 

Seriously great fun but of course PCM and DSD are different but the degree of difference is all one of perspective! For example it has been suggested that DSD has been produced by SDM but PCM not, yet we know that most PCM actually arises from SDM DAC, likewise most PCM is processed via SDM in most DACs, so really from an entirely practical POV there are conversions — and honestly I fail to see a very crisp practical distinction

[asdf1000]

21 minutes ago, jabbr said:

really having great fun watching

 

This has been entertaining for all, even us on the sidelines.

 

Once a month or so, something erupts and we get a classic like this.

 

Lots of great info of course too, for learning purposes - for me anyway.

 

[Paul R]

5 hours ago, Miska said:

 

https://www.sonarnerd.net/tmp/sweep2-1.zip

 

Just one example of course.

 

Pretty cool actually...

[Paul R]

37 minutes ago, jabbr said:

 

Oohhh metaphysics!

 

That question is definitely beyond my pay grade. 

 

😱 Gads, I hope not! If you are getting paid for this stuff, I have a few tech questions I need some help with... 

 

 

Quote

 

 

I hope the differences between PCM and DSD can be answered by math/physics and don’t need to invoke a higher power ( @Miska? 😂)

 

I’ve been playing Devil’s advocate here of course and really having great fun watching @mansr arguing one point with one hand and at the same time arguing against me, even when I’m siding with him on the other side of your argument. I’ve been wondering if he will simply cease to exist due to an internal logical inconsistency ( @Miska this is a joke in case you are wondering! 😂😂😂)

 

Seriously great fun but of course PCM and DSD are different but the degree of difference is all one of perspective! For example it has been suggested that DSD has been produced by SDM but PCM not, yet we know that most PCM actually arises from SDM DAC, likewise most PCM is processed via SDM in most DACs, so really from an entirely practical POV there are conversions — and honestly I fail to see a very crisp practical distinction

 

Different applications for different things. Would you speak COBOL at a diplomatic dinner?

 

https://www.electronicdesign.com/analog/turn-spreadsheet-delta-sigma-modulator

 

The above is an older article that tells you how to build a simple spreadsheet to play with PDM. It's- instructive. Also kinda fun.  

 

-Paul

 

[jabbr]

5 hours ago, Miska said:

 

https://www.sonarnerd.net/tmp/sweep2-1.zip

 

Just one example of course.

 

That's music, eh? 🙄

[Jud]

2 hours ago, jabbr said:

most PCM actually arises from SDM DAC

 

Eh?

[jabbr]

1 hour ago, Paul R said:

😱 Gads, I hope not! If you are getting paid for this stuff, I have a few tech questions I need some help with... 

 

If you don't believe in a higher power, then life really is a series of (albeit highly complex) chemical reactions. If you do believe in a higher power then Francis Collins' "Language of God", but I've heard the mind- body duality debated in college too many times to have the energy to comment further ... 

 

I think your point is that two things can be the same on one level of the conceptual stack, and radically different on a different level. PCM and DSD are thus. The DAC electronics might be fairly similar, but conceptually the two are different. Likewise different modulators and processing might lead to different audible effects. So similarly although we can explain all of electromagnetics using Maxwell's equations, its not useful in many situations. Digital software is vastly more understandable to describe the output of digital computers.

 

Of course.

[jabbr]

10 minutes ago, Jud said:

 

Eh?

Whoops ... I meant to write that "Most PCM arises from SDM ADC" ... that is to say, an early step in a typical ADC is a sigma-delta modulation block, e.g.:

https://www.analog.com/media/en/technical-documentation/data-sheets/ad1871.pdf

 

Sigma-delta modulation isn't always used as part of the process of producing  PCM encoding, but most often according to what I've read.

[Allan F]

2 hours ago, Paul R said:

Different applications for different things. Would you speak COBOL at a diplomatic dinner?

 

Probably, if the alternative was to speak FORTRAN.

[pkane2001]

1 hour ago, jabbr said:

 

That's music, eh? 🙄

 

Here you go. music:  https://drive.google.com/open?id=1tOx3CdUxpLRej4E4BpnP-iA8y-z8jXo-

 

[Miska]

4 hours ago, pkane2001 said:

Here you go. music:  https://drive.google.com/open?id=1tOx3CdUxpLRej4E4BpnP-iA8y-z8jXo-

 

That isn't 1-bit data, but anyway...