D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org)

[Les Cargill[_4_]]

https://www.youtube.com/watch?v=cIQ9IXSUzuM

[[email protected]]

On Wednesday, March 9, 2016 at 1:14:07 PM UTC-5, Les Cargill wrote:
> https://www.youtube.com/watch?v=cIQ9IXSUzuM

This is a nice video and the message is good, but the details are a bit wrong.

The author says the audio NEVER is stairstepped.

In fact, the audio IS STAIRSTEPPED before the reconstruction filter.

That is the purpose of the reconstruction filter.

The reconstruction filter is just a low pass filter that removes all the
frequencies above 22.05 kHz (for 44.1 ksps). Removing the frequencies above 22.05 kHz is what removes the stairsteps.


In fact, you can see the stairsteps on a few of the scope shots, so I don't understand how the author can claim they NEVER exist.


Mark

[Don Pearce[_3_]]

On Thu, 10 Mar 2016 06:24:53 -0800 (PST), wrote:

>On Wednesday, March 9, 2016 at 1:14:07 PM UTC-5, Les Cargill wrote:
>> https://www.youtube.com/watch?v=cIQ9IXSUzuM
>
>This is a nice video and the message is good, but the details are a bit wrong.
>
>The author says the audio NEVER is stairstepped.
>
>In fact, the audio IS STAIRSTEPPED before the reconstruction filter.
>
>That is the purpose of the reconstruction filter.
>
>The reconstruction filter is just a low pass filter that removes all the
>frequencies above 22.05 kHz (for 44.1 ksps). Removing the frequencies above 22.05 kHz is what removes the stairsteps.
>
>
>In fact, you can see the stairsteps on a few of the scope shots, so I don't understand how the author can claim they NEVER exist.
>
>
>Mark
>
>

He might argue with some justification that it only becomes audio
after the final stage - the reconstruction filter. At that point he is
right - there are no stair steps.

d

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[Scott Dorsey]

> wrote:
>The author says the audio NEVER is stairstepped.
>
>In fact, the audio IS STAIRSTEPPED before the reconstruction filter.
>
>That is the purpose of the reconstruction filter.
>
>The reconstruction filter is just a low pass filter that removes all the
>frequencies above 22.05 kHz (for 44.1 ksps). Removing the frequencies above 22.05 kHz is what removes the stairsteps.

Here we go again...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Les Cargill[_4_]]

wrote:
> On Wednesday, March 9, 2016 at 1:14:07 PM UTC-5, Les Cargill wrote:
>> https://www.youtube.com/watch?v=cIQ9IXSUzuM
>
> This is a nice video and the message is good, but the details are a bit wrong.
>
> The author says the audio NEVER is stairstepped.
>
> In fact, the audio IS STAIRSTEPPED before the reconstruction filter.
>
> That is the purpose of the reconstruction filter.
>

And that is the point of his demonstration. I don't know how you'd find
disagreement with him on that. :) I read this as his demonstrating
"this is what the reconstruction filter does".

Is this the sort of thing that was modestly rushed in the presentation
or something? Given the wrong emphasis? I think you found a "bug" but
I'm not sure of the nature of said bug.

In the case with higher frequency signals, the waveform is
*BEYOND* stairstepped ( it looks like modern art! or a Formica
pattern) , and then he shows you the actual output, which is not.

> The reconstruction filter is just a low pass filter that removes all the
> frequencies above 22.05 kHz (for 44.1 ksps). Removing the frequencies above 22.05 kHz is what removes the stairsteps.
>
>
> In fact, you can see the stairsteps on a few of the scope shots, so I don't understand how the author can claim they NEVER exist.
>
>

They only exist before the reconstruction filter. I didn't hear him say
anything that contradicts that.

But I saw the demo with the eyes of someone who's already familiar with
the subject so I may have filtered small errors in presentation.

> Mark
>
>
>

--
Les Cargill

[[email protected]]

On Thursday, March 10, 2016 at 12:49:16 PM UTC-5, Les Cargill wrote:
> wrote:
> > On Wednesday, March 9, 2016 at 1:14:07 PM UTC-5, Les Cargill wrote:
> >> https://www.youtube.com/watch?v=cIQ9IXSUzuM
> >
> > This is a nice video and the message is good, but the details are a bit wrong.
> >
> > The author says the audio NEVER is stairstepped.
> >
> > In fact, the audio IS STAIRSTEPPED before the reconstruction filter.
> >
> > That is the purpose of the reconstruction filter.
> >
>
> And that is the point of his demonstration. I don't know how you'd find
> disagreement with him on that. :) I read this as his demonstrating
> "this is what the reconstruction filter does".
>
> Is this the sort of thing that was modestly rushed in the presentation
> or something? Given the wrong emphasis? I think you found a "bug" but
> I'm not sure of the nature of said bug.
>
> In the case with higher frequency signals, the waveform is
> *BEYOND* stairstepped ( it looks like modern art! or a Formica
> pattern) , and then he shows you the actual output, which is not.
>
> > The reconstruction filter is just a low pass filter that removes all the
> > frequencies above 22.05 kHz (for 44.1 ksps). Removing the frequencies above 22.05 kHz is what removes the stairsteps.
> >
> >
> > In fact, you can see the stairsteps on a few of the scope shots, so I don't understand how the author can claim they NEVER exist.
> >
> >
>
> They only exist before the reconstruction filter. I didn't hear him say
> anything that contradicts that.
>
> But I saw the demo with the eyes of someone who's already familiar with
> the subject so I may have filtered small errors in presentation.
>
> > Mark
> >
> >
> >
>
> --
> Les Cargill

I agree, the point of the video would have been better stated if he had said,
"the reconstruction filter inside the D/A box removes the stairsteps so you will never hear them".

instead he said, the starsteps don't EVER exist anywhere in the system and he never mentions the reconstruction filter.

The stairsteps of course do exit inside the D/A system but they are removed by the reconstruction filter before "the audio" gets to your ears.

If the reconstruction filter is perfect, the audio is perfect.

[Mike Rivers[_2_]]

On 3/10/2016 9:24 AM, wrote:
> This is a nice video and the message is good, but the details are a bit wrong.
>
> The author says the audio NEVER is stairstepped.
>
> In fact, the audio IS STAIRSTEPPED before the reconstruction filter.

You missed his point about what's stairstepped and what isn't. During
the sampling process, you have discrete voltages, but they aren't
connected. There's no continuous steady voltage measured between two
samples. It could be anything and you'd miss it. The stairsteps that he
shows are graphical, not electrical.

--
For a good time, visit http://mikeriversaudio.wordpress.com

[Mike Rivers[_2_]]

On 3/10/2016 12:54 PM, Scott Dorsey wrote:
> Here we go again...

There seems to be no way to explain sampling to a non-believer.

--
For a good time, visit http://mikeriversaudio.wordpress.com

[Don Pearce[_3_]]

On Thu, 10 Mar 2016 14:59:18 -0500, Mike Rivers >
wrote:

>On 3/10/2016 9:24 AM, wrote:
>> This is a nice video and the message is good, but the details are a bit wrong.
>>
>> The author says the audio NEVER is stairstepped.
>>
>> In fact, the audio IS STAIRSTEPPED before the reconstruction filter.
>
>You missed his point about what's stairstepped and what isn't. During
>the sampling process, you have discrete voltages, but they aren't
>connected. There's no continuous steady voltage measured between two
>samples. It could be anything and you'd miss it. The stairsteps that he
>shows are graphical, not electrical.

Still available, my short paper on dither in audio. I think it
explains what is going on fairly well. I haven't seen a reason to
change it in the years since I wrote it, anyway.

http://www.soundthoughts.co.uk/read/dither.htm

d

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[geoff]

On 11/03/2016 9:00 a.m., Mike Rivers wrote:
> On 3/10/2016 12:54 PM, Scott Dorsey wrote:
>> Here we go again...
>
> There seems to be no way to explain sampling to a non-believer.
>


And a lot of Neil's music is downright depressing. Those (mostly older)
uplifting ones do remain absolutely magic though ...

geff

[JackA]

On Thursday, March 10, 2016 at 9:25:08 AM UTC-5, wrote:
> On Wednesday, March 9, 2016 at 1:14:07 PM UTC-5, Les Cargill wrote:
> > https://www.youtube.com/watch?v=cIQ9IXSUzuM
>
> This is a nice video and the message is good, but the details are a bit wrong.
>
> The author says the audio NEVER is stairstepped.
>
> In fact, the audio IS STAIRSTEPPED before the reconstruction filter.
>
> That is the purpose of the reconstruction filter.

I agree with Mark. That was actually shown on an oscilloscope (before/after) on the same site I found out about the magical 3kHz, that I'm often teased about.

Jack

>
> The reconstruction filter is just a low pass filter that removes all the
> frequencies above 22.05 kHz (for 44.1 ksps). Removing the frequencies above 22.05 kHz is what removes the stairsteps.
>
>
> In fact, you can see the stairsteps on a few of the scope shots, so I don't understand how the author can claim they NEVER exist.
>
>
> Mark

[jason]

On Thu, 10 Mar 2016 20:26:30 GMT "Don Pearce" > wrote in
article >
> http://www.soundthoughts.co.uk/read/dither.htm
>

Thanks.

[[email protected]]

On Thursday, March 10, 2016 at 3:00:30 PM UTC-5, Mike Rivers wrote:
> On 3/10/2016 12:54 PM, Scott Dorsey wrote:
> > Here we go again...
>
> There seems to be no way to explain sampling to a non-believer.
>


I see how easy it is to be misunderstood here.

I'm agreeing there are no steps after the reconstruction filter therefore steps are NOT an issue for audio.See I DO beleive.


Steps however DO exist inside the D/A box, after the D/A and before the reconstruction filter.

The author of the video claims there are no stairsteps ANYWHERE in any part of the system and this is clearly wrong because he shows a scope trace that clearly shows the steps. (Real hardware usually has a zero order hold, so yes steps really are there, not impulses.)


I'm not saying steps are a problem.
I'm saying the author did not correctly explain the reason they are not a problem.


If you don't agree, then you don't understand.

M

[Scott Dorsey]

> wrote:
>I see how easy it is to be misunderstood here.
>
>I'm agreeing there are no steps after the reconstruction filter therefore s=
>teps are NOT an issue for audio.See I DO beleive.

It's not that I am arguing about this when I say "here we go again." Although
today we have a lot of converters that aren't ladder converters at all (in
fact you will be hard-pressed to find a ladder converter today) so the whole
notion of the "stairstep" no longer exists with many devices. With many
sigma-delta converters the summing stage _is_ the reconstruction filter.

What I am saying when I say "here we go again" is that this same discussion
has been brought up over and over and over again in this channel for 25 years.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[JackA]

On Friday, March 11, 2016 at 8:45:42 AM UTC-5, Scott Dorsey wrote:
> > wrote:
> >I see how easy it is to be misunderstood here.
> >
> >I'm agreeing there are no steps after the reconstruction filter therefore s=
> >teps are NOT an issue for audio.See I DO beleive.
>
> It's not that I am arguing about this when I say "here we go again." Although
> today we have a lot of converters that aren't ladder converters at all (in
> fact you will be hard-pressed to find a ladder converter today) so the whole
> notion of the "stairstep" no longer exists with many devices. With many
> sigma-delta converters the summing stage _is_ the reconstruction filter.
>
> What I am saying when I say "here we go again" is that this same discussion
> has been brought up over and over and over again in this channel for 25 years.
> --scott
>
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

And Scott and I didn't hit it off well, when an innocent bystander was criticized, by Scott, for not soldering a plastic switch. I, one the other hand, with the gift of logic, think before I instruct someone to solder, feeling they may DESTROY whatever they are soldering.

And I do thank OTHERS outside of usenet, for mentioning about Sony's PCM machines that were the cause for many ill sounding CDs. Little to do with D/A converters. Now, at least, Scott knows the truth.

Jack