[Jerry Avins]

Floyd L. Davidson wrote:
Jerry Avins wrote:
Floyd L. Davidson wrote:
Jerry Avins wrote:
... A signal can be
quantized without any need to measure it or describe it
with a number.
That isn't true. In order to quantize it you *must*
decide on non-overlapping ranges of *values*, and a
specific quantity value that equates to those values.

An example is the signal being measured
in a quantum Hall-effect experiment.
Explain.
http://www.warwick.ac.uk/~phsbm/qhe.htm

Why don't you tell us what you think this means. I
have no need to spend my time tracking down your
comments.

Live and learn, or live and don't learn. Your choice. I'm indifferent.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

Floyd L. Davidson wrote:
Don Bowey wrote:
On 8/20/07 5:43 PM, in article , "Floyd L.
Davidson" wrote:

(Don Pearce) wrote:
On 20 Aug 2007 21:42:18 GMT, Scott Seidman
wrote:

(Floyd L. Davidson) wrote in
:

quantized - a sampled signal, but with the possible levels constrained
to a limited set of values
That is by definition a digital siganl. As soon as the possible values
are "constrained to a limited set", it is by definition digital data.


Wouldn't this make the output of a D/A converter digital by definition?
It certainly would. But apparently there are those that can't see the
difference between a limited set of values, and a set of numbers
describing those values.
You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...
Including a two foot piece of cable, or two inches with a small cap.

Nope. It would take a fair sized cap.

Keep in mind that that is *exactly* what a V.90 modem puts on a
regular twisted pair telephone cable, and it works just fine for
a couple miles at least, sometimes even much farther.

And that signal is digital, and is processed as a digital signal
by the receiving modem.

The signal is amplified in analog repeaters and again in the modem. Your
categories are too hard edged. The very purpose of a modem is converting
digital signal to analog that can traverse an analog phone line and back
again to digital at the far end. A modem might be the worst example of a
purely digital I can imagine.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

isw wrote:
In article ,
Jerry Avins wrote:

Radium wrote:
Hi:

I. Audio vs. Video

Digitized (mono) audio has a single sample per each sampling
interval.
Yes. several bits per sample, many samples per second.

In the case of digital video, we could treat each individual sample
point location in the sampling grid (each pixel position in a frame)
the same way as if it was a sample from an individual (mono) audio
signal that continues on the same position in the next frame. For
example, a 640?480 pixel video stream shot at 30 fps would be treated
mathematically as if it consisted of 307200 parallel, individual mono
audio streams [channels] at a 30 Hz sample rate. Where does bit-
resolution enter the equation?
It might actually make sense to look at it that way in some situations,
but I'll bet you can't think of one.

How about a T1 (DS1) stream? It's a series of 8-bit audio samples, with
frame sync.

Isaac

Are you Radium in disguise? My bet was with him.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Floyd L. Davidson]

Don Bowey wrote:
On 8/20/07 8:14 PM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 5:43 PM, in article , "Floyd L.
Davidson" wrote:

(Don Pearce) wrote:
On 20 Aug 2007 21:42:18 GMT, Scott Seidman
wrote:

(Floyd L. Davidson) wrote in
:

quantized - a sampled signal, but with the possible levels constrained
to a limited set of values

That is by definition a digital siganl. As soon as the possible values
are "constrained to a limited set", it is by definition digital data.



Wouldn't this make the output of a D/A converter digital by definition?

It certainly would. But apparently there are those that can't see the
difference between a limited set of values, and a set of numbers
describing those values.

You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...

Including a two foot piece of cable, or two inches with a small cap.

Nope. It would take a fair sized cap.

Keep in mind that that is *exactly* what a V.90 modem puts on a
regular twisted pair telephone cable, and it works just fine for
a couple miles at least, sometimes even much farther.

And that signal is digital, and is processed as a digital signal
by the receiving modem.

Digital data CSUs and T1 transmitter line signals are digital and look
similar to distorted square waves. An all 1's signal looks like a distorted
sinewave .

Your point is? (Besides the poor description? They
don't look like distorted square waves. The look like
only slightly distorted sine waves!)

Using the same V.90 example....... It will work as well if two v.90 modems
are connected back-to-back by a short pair of wires.

It won't. They can't talk to each other that way except
using v.34 protocols.

Regardless, what is your point? I said that v.90 works
fine for a couple of *miles*, minimum, so what
significance would there be to working "back-to-back by
a short pair of wires"?

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

Jerry Avins wrote:
Floyd L. Davidson wrote:
Jerry Avins wrote:
Floyd L. Davidson wrote:
Jerry Avins wrote:
...

I can
demonstrate a circuit using analog components that
transforms a continuous ramp input into a staircase
output. Moreover, the output levels can be individually
adjusted. Is the output digital? (We're discussing an
arbitrary definition here. There is no wrong answer.)
The output is apparenlty analog. At least you have
said
*nothing* that indicates otherwise.
Apparently analog but actually digital? That would be in
keeping with your assertion that quantizing an otherwise
analog signal digitizes it.
You *didn't* quantize it. Or at least nothing you said
assures that it has been quantized, and given "levels can
be individually adjusted" is high suggests that it is not
quantized.

Do you think all digital signals are square waves and
anything that has square waves is digital? Your example
above suggests that you might, but it simply isn't true.
By old vacuum-tube signal generator was certainly
analog. It produced square waves among other wave shapes.
Hot damned, you *are* aware of that. Amazing...

You know, Floyd, legal definitions don't always reflect
reality.

You know Jerry, *technical* definitions are reality.

You can fight it all you like, but it won't change the
fact that to talk to anyone about this topic *requires* that
we all use the same definitions, and the ones that I've
cited *are* the standard definitions used by *everyone*
that is credible.

....
law read. I remember the judges words: "You're a little
snotnose. I'd love to fine you for speeding, but you're
not charged with that. Case dismissed!"

I'm still a little snotnose, and partitioning a signal
into approximate levels -- because of noise the levels
can never be exact -- doesn't make it digital *in fact*,
whatever the gummint might declare.

You aren't a little snotnose. Your just a little
foolish, that's all. Everyone is about something, and
that's where you've chosen to make your stand.

Regardless of how silly you want to be, it *does* make
it digital, by definition.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

Jerry Avins wrote:
Floyd L. Davidson wrote:
Jerry Avins wrote:
Floyd L. Davidson wrote:
Jerry Avins wrote:
... A signal can be
quantized without any need to measure it or describe it
with a number.
That isn't true. In order to quantize it you *must*
decide on non-overlapping ranges of *values*, and a
specific quantity value that equates to those values.

An example is the signal being measured
in a quantum Hall-effect experiment.
Explain.
http://www.warwick.ac.uk/~phsbm/qhe.htm
Why don't you tell us what you think this means. I
have no need to spend my time tracking down your
comments.

Live and learn, or live and don't learn. Your choice. I'm indifferent.

I noticed that you have no intention of learning anything.

My point was that I see *nothing* on that web page which
supports anything you've stated. If you do, be my guest
and make an even greater fool of yourself than you have
at this point.


--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

Jerry Avins wrote:
Floyd L. Davidson wrote:
Don Bowey wrote:
On 8/20/07 5:43 PM, in article , "Floyd L.
Davidson" wrote:

(Don Pearce) wrote:
On 20 Aug 2007 21:42:18 GMT, Scott Seidman
wrote:

(Floyd L. Davidson) wrote in
:

quantized - a sampled signal, but with the possible levels constrained
to a limited set of values
That is by definition a digital siganl. As soon as the possible values
are "constrained to a limited set", it is by definition digital data.


Wouldn't this make the output of a D/A converter digital by definition?
It certainly would. But apparently there are those that can't see the
difference between a limited set of values, and a set of numbers
describing those values.
You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...
Including a two foot piece of cable, or two inches with a small cap.
Nope. It would take a fair sized cap.
Keep in mind that that is *exactly* what a V.90 modem
puts on a
regular twisted pair telephone cable, and it works just fine for
a couple miles at least, sometimes even much farther.
And that signal is digital, and is processed as a
digital signal
by the receiving modem.

The signal is amplified in analog repeaters and again in
the modem.

There simply are no such things as "analog repeaters"
on local telephone loops.

Where do you get these funny ideas.

Your categories are too hard edged.

There isn't any other way.

The very
purpose of a modem is converting digital signal to
analog that can traverse an analog phone line and back
again to digital at the far end. A modem might be the
worst example of a purely digital I can imagine.

A "modem" can't be "purely digital", because it
necessarily has a digital side and an analog side. But
a v.90 modem is a bit different, because it is indeed a
modem for the *uplink*, which uses v.34 protocols. It
is *not* a modem for the downlink, but instead is a
digital encoder.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Don Pearce]

On Mon, 20 Aug 2007 16:38:18 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
On Mon, 20 Aug 2007 13:38:15 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
Sorry, but that is simply nonsense. A signal that is sampled in time,
but not quantized is an analogue signal. It is treated and processed
by analogue circuits. For a signal to be digital its sampled levels
must be represented by numbers, which are processed mathematically by
some sort of microprocessor.

That is, it must actually be quantized.

Perhaps that is what you meant to say earlier, but you
actually didn't, and said that the quantized signal has
to be represented by numbers, which it is by definition.

No it isn't -

It is by definition. You can stand there and deny it all
you like, but that just makes *you* look damned silly.

I've cited impeccable and authoritative sources. You have not
and cannnot cite anything that supports your opinion.

You have cited a source that is describing something else. It is a
source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat
that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.

it can simply be a signal where the smooth curve has
been replaced by steps. If you want to process that signal you must do
so with analogue circuitry - amplifiers, filters etc. Representing
those steps by numbers is a different matter. Once you have done that,
you can no longer process in the analogue domain, you must use maths
on the numbers; that is what makes it digital.

The signal can be reconverted to an
analogue one later by a D to A.

It's best to call that a quasi-analog signal...

No it isn't. It is an analogue signal, because it is no longer
represented by digits.

Keep denying all you like Don. You can't cite anyone credible
that supports your whacko definitions.

I am the credible source, because I know what I am talking about.

But clearly you are right in your appeal to authority. Tell you what I
will do. I will examine some analogue audio waveforms today to see if
I can find any parts of them that are in fact digital. They will be
easy to recognise because there will be brief moments where they are
flat. That will make them digital by your definition.

And perhaps I will look at the digital signal recovered by my DAB
radio. That is band limited and contains no flat bits and steps at all
- in fact it looks a bit like a bendy almost-sine wave. That'll be
analogue by your definition.

d
--
Pearce Consulting
http://www.pearce.uk.com

[Don Bowey]

On 8/20/07 10:19 PM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 8:14 PM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 5:43 PM, in article , "Floyd L.
Davidson" wrote:

(Don Pearce) wrote:
On 20 Aug 2007 21:42:18 GMT, Scott Seidman
wrote:

(Floyd L. Davidson) wrote in
:

quantized - a sampled signal, but with the possible levels constrained
to a limited set of values

That is by definition a digital siganl. As soon as the possible values
are "constrained to a limited set", it is by definition digital data.



Wouldn't this make the output of a D/A converter digital by definition?

It certainly would. But apparently there are those that can't see the
difference between a limited set of values, and a set of numbers
describing those values.

You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...

Including a two foot piece of cable, or two inches with a small cap.

Nope. It would take a fair sized cap.

Keep in mind that that is *exactly* what a V.90 modem puts on a
regular twisted pair telephone cable, and it works just fine for
a couple miles at least, sometimes even much farther.

And that signal is digital, and is processed as a digital signal
by the receiving modem.

Digital data CSUs and T1 transmitter line signals are digital and look
similar to distorted square waves. An all 1's signal looks like a distorted
sinewave .

Your point is? (Besides the poor description? They
don't look like distorted square waves. The look like
only slightly distorted sine waves!)

Have you looked at a DSX-1 envelope lately?


Using the same V.90 example....... It will work as well if two v.90 modems
are connected back-to-back by a short pair of wires.

It won't. They can't talk to each other that way except
using v.34 protocols.

Regardless, what is your point? I said that v.90 works
fine for a couple of *miles*, minimum, so what
significance would there be to working "back-to-back by
a short pair of wires"?

My point is...... You are making too much of your point that "Of course if
you then run that digital PAM signal through virtually any analog channel,
it no longer has a limited set of values."

[Don Pearce]

On Mon, 20 Aug 2007 16:29:46 -0800, (Floyd L.
Davidson) wrote:

Scott Seidman wrote:
(Floyd L. Davidson) wrote in
:

Sheesh! That *is*, by definition a digital signal.


Funny, that's just what my D/A converters put out, and the spec sheets
claim they're putting out analog signals. Perhaps I should return them.

Your D/A converter puts out what is called
"quasi-analog". It's actually a digital PAM signal, not
an analog signal.

You can easily make it is a close approximation of the
original (with quantization distortion added), however,

But once you do that (by sending it through almost any
kind of an analog channel) it truly becomes "analog", in
the sense that you can no longer recover information or
use it as a digital signal.

This just goes on getting funnier by the post.

d

--
Pearce Consulting
http://www.pearce.uk.com

[Ray Fischer]

Radium wrote:
On Aug 19, 2:50 pm, (Ray Fischer) wrote:

Radium wrote:

Hi:

I. Audio vs. Video

Digitized (mono) audio has a single sample per each sampling
interval.

In the case of digital video, we could treat each individual sample
point location in the sampling grid (each pixel position in a frame)
the same way as if it was a sample from an individual (mono) audio
signal that continues on the same position in the next frame. For
example, a 640×480 pixel video stream shot at 30 fps would be treated
mathematically as if it consisted of 307200 parallel, individual mono
audio streams [channels] at a 30 Hz sample rate. Where does bit-
resolution enter the equation?

Digital linear PCM audio has the following components:

1. Sample rate [44.1 KHz for CD audio]
2. Channels [2 in stereo, 1 in monaural]
3. Bit-resolution [16-bit for CD audio]

Sample rate in audio = frame rate in video
Channel in audio = pixel in video
Bit-resolution in audio = ? in video

Is it true that unlike the-frequency-of-audio, the-frequency-of-video
has two components -- temporal and spatial?

No. Video is converted to a linear data stream corresponding
(roughly) to scan lines. The color and brightness information
is split apart and converted into parallel data streams.

Okay. So a digital video device with greater bit-resolution can allow
for more levels of luminance?

Yes.

What is the video-equivalent of bit-resolution?

Analog or digital?

Compression for digital video may group areas of the image
and/or eliminate some of the color components.

Does compression also eliminate some of the brightness components?

Not usually.

II. Digital vs. Analog

Sample-rate is a digital entity. In a digital audio device, the sample-
rate must be at least 2x the highest intended frequency of the digital
audio signal. What is the analog-equivalent of sample-rate?

There is no sampling in analog so there is no sampling rate.

There is no analog-equivalent of sample-rate? Then what the limits the
highest frequency an analog audio device can encode?

Usually the capacitance and inductance of the circuits.

What determines the highest frequency signal an analog solid-state
audio device can input without distortion?

Analog solid-state audio device = a purely analog electronic device
that can record, store, playback, and process audio signals without
needing any moving parts.

No such thing.

The above device inputs the electrical signals generated by an
attached microphone. These electric signals are AC and represent the
sound in "electronic" form. Sound with a higher-frequency will
generate a faster-alternating current than sound with a lower-
frequency. A louder sound will generate an alternating-current with a
bigger peak-to-peak wattage than a softer soft.

What mathematically determines the highest-frequency electric signal
such a device can intake without distortion?

For that you need a degree in electrical engineering.

--
Ray Fischer

[Don Pearce]

On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:


A "quantized analogue signal" is digital by definition.


No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.

It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

d

--
Pearce Consulting
http://www.pearce.uk.com

[Don Bowey]

On 8/20/07 10:31 PM, in article , "Floyd L.
Davidson" wrote:


There simply are no such things as "analog repeaters"
on local telephone loops.

Since when?

If a loop is long enough, and there is no pair-gain facility available, it
gets an "E" type repeater. If that isn't an analog repeater nothing is.



Where do you get these funny ideas.

(snip)

[Jerry Avins]

Don Pearce wrote:
On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:

A "quantized analogue signal" is digital by definition.

No, you haven't. You merely have a signal at a set of discrete levels.
Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.
It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

Reverse the order of operations and the attenuator becomes the D-to-A
and the amplifier will be an A-to-D (if the gain is right). Don't worry
about loss of SNR by attenuating first. That shouldn't matter as long as
the signal ends up digital again. :-)

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Floyd L. Davidson]

(Don Pearce) wrote:
On Mon, 20 Aug 2007 16:38:18 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
On Mon, 20 Aug 2007 13:38:15 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
Sorry, but that is simply nonsense. A signal that is sampled in time,
but not quantized is an analogue signal. It is treated and processed
by analogue circuits. For a signal to be digital its sampled levels
must be represented by numbers, which are processed mathematically by
some sort of microprocessor.

That is, it must actually be quantized.

Perhaps that is what you meant to say earlier, but you
actually didn't, and said that the quantized signal has
to be represented by numbers, which it is by definition.

No it isn't -

It is by definition. You can stand there and deny it all
you like, but that just makes *you* look damned silly.

I've cited impeccable and authoritative sources. You have not
and cannnot cite anything that supports your opinion.

You have cited a source that is describing something else. It is a

Bull**** Don, that is abjectly stupid to claim.

source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat
that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.

Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.

Apparently *you* don't understand it. What they say is
correct. If you think otherwise, be my guest...

it can simply be a signal where the smooth curve has
been replaced by steps. If you want to process that signal you must do
so with analogue circuitry - amplifiers, filters etc. Representing
those steps by numbers is a different matter. Once you have done that,
you can no longer process in the analogue domain, you must use maths
on the numbers; that is what makes it digital.

The signal can be reconverted to an
analogue one later by a D to A.

It's best to call that a quasi-analog signal...

No it isn't. It is an analogue signal, because it is no longer
represented by digits.

Keep denying all you like Don. You can't cite anyone credible
that supports your whacko definitions.

I am the credible source, because I know what I am talking about.

You are not even close to being a credible source Don.
And not that you cannot find *anyone* who is credible that
agrees with you.

But clearly you are right in your appeal to authority. Tell you what I
will do. I will examine some analogue audio waveforms today to see if
I can find any parts of them that are in fact digital. They will be
easy to recognise because there will be brief moments where they are
flat. That will make them digital by your definition.

How do you figure that?

And perhaps I will look at the digital signal recovered by my DAB
radio. That is band limited and contains no flat bits and steps at all
- in fact it looks a bit like a bendy almost-sine wave. That'll be
analogue by your definition.

Don, you have made it abundantly clear that you don't
understand this topic at all.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Don Pearce]

On Tue, 21 Aug 2007 02:13:22 -0400, Jerry Avins wrote:

Don Pearce wrote:
On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:

A "quantized analogue signal" is digital by definition.

No, you haven't. You merely have a signal at a set of discrete levels.
Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.
It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

Reverse the order of operations and the attenuator becomes the D-to-A
and the amplifier will be an A-to-D (if the gain is right). Don't worry
about loss of SNR by attenuating first. That shouldn't matter as long as
the signal ends up digital again. :-)

Jerry

Bloody hell, I hadn't thought of that. Electronics is suddenly taking
on a whole new set of meanings for me.

I wonder what a tone control is. I mean it must be a D to A converter
for some bits of a signal, and an A to D for other bits. And of course
if you should ever drive an amplifier into overload, you have instant
digital data. The world is all of a sudden quite wonderful - but if I
click my heels together will I find myself back in Kansas?

d

--
Pearce Consulting
http://www.pearce.uk.com

[Floyd L. Davidson]

Don Bowey wrote:
On 8/20/07 10:19 PM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 8:14 PM, in article , "Floyd L.
Davidson" wrote:

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...

Including a two foot piece of cable, or two inches with a small cap.

Nope. It would take a fair sized cap.

Keep in mind that that is *exactly* what a V.90 modem puts on a
regular twisted pair telephone cable, and it works just fine for
a couple miles at least, sometimes even much farther.

And that signal is digital, and is processed as a digital signal
by the receiving modem.

Digital data CSUs and T1 transmitter line signals are digital and look
similar to distorted square waves. An all 1's signal looks like a distorted
sinewave .

Your point is? (Besides the poor description? They
don't look like distorted square waves. The look like
only slightly distorted sine waves!)

Have you looked at a DSX-1 envelope lately?

Yes. I've got the specs right here! :-) Literally, I have
had a graph on my web site for several years now that I drew up
to illustrate something I wrote once upon a time

http://www.apaflo.com/floyd_davidson/t1pulse.jpg


Using the same V.90 example....... It will work as well if two v.90 modems
are connected back-to-back by a short pair of wires.

It won't. They can't talk to each other that way except
using v.34 protocols.

Regardless, what is your point? I said that v.90 works
fine for a couple of *miles*, minimum, so what
significance would there be to working "back-to-back by
a short pair of wires"?

My point is...... You are making too much of your point that "Of course if
you then run that digital PAM signal through virtually any analog channel,
it no longer has a limited set of values."

Yeah, your are probably right on that one. I should
have left the "virtually any" out, and just said "an
analog channel". It depends greatly on the
characteristics of the channel, and it happens that a
wireline is a pretty "good" channel, while many
amplifiers would not be so good.

Sorry if I'm getting a bit cranky here, the abject
silliness being displayed by a couple of people is
annoying.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Don Pearce]

On Mon, 20 Aug 2007 22:14:45 -0800, (Floyd L.
Davidson) wrote:

source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat
that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.

Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.

Apparently *you* don't understand it. What they say is
correct. If you think otherwise, be my guest...

Actually I was talking about this:

Nyquist's theorem: A theorem, developed by H. Nyquist, which states
that an analog signal waveform may be uniquely reconstructed, without
error, from samples taken at equal time intervals. The sampling rate
must be equal to, or greater than, twice the highest frequency
component in the analog signal. Synonym sampling theorem.

Go ahead and defend.

d

--
Pearce Consulting
http://www.pearce.uk.com

[Floyd L. Davidson]

(Don Pearce) wrote:
On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:


A "quantized analogue signal" is digital by definition.


No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.

It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Well, analog amplifiers generally have upper limits for frequencies
that they will pass. There's all sorts of phase distortion which
occurs when the frequency response drops off. That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.

I know you don't understand that, but everything else seems hard
for you too.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

If you think about the above for awhile, you're in for a big
surprise.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Don Pearce]

On Mon, 20 Aug 2007 22:36:22 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:


A "quantized analogue signal" is digital by definition.


No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.

It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Well, analog amplifiers generally have upper limits for frequencies
that they will pass. There's all sorts of phase distortion which
occurs when the frequency response drops off. That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.


Bull****. Unless of course you are claiming that all digital signals
have perfectly flat tops and vertical edges. Is that your claim,
Floyd? You are no longer waving, but drowning. Just admit you have
this all wrong and bow out with as much grace as you can manage.

I know you don't understand that, but everything else seems hard
for you too.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

If you think about the above for awhile, you're in for a big
surprise.

All of a sudden he has no answer. Come on Floyd - it is your claim
that an amplifier is a D to A converter. Now put up or shut up. Defend
it or admit you have screwed up.

d

--
Pearce Consulting
http://www.pearce.uk.com

[Steve Underwood]

glen herrmannsfeldt wrote:
Dave Platt wrote:

(snip)

Some of the TV networks are speeding up syndicated reruns by using
this sort of technique. They appear to be using the "chop out audio
samples" method to speed up the dialog (without pitch-shifting it) and
dropping out complete frames of the video. This works fairly well
when watching scenes with little action, but causes an odd
stuttering-jerk effect when the camera pans or somebody walks across
the screen.

I have a VCR that will play back at 1.5X without pitch shifting.
At higher playback speeds at only gives you part of the sound.
Maybe two second pieces with gaps depending on the speed.

The 1.5X playback is just a little too fast to watch a show
comfortably.

A lot of relatively simple variable speed constant pitch playback
techniques - e.g. various TDHS derivatives, like PICOLA or PSOLA - work
well up to x1.5 or so. They start to sound nasty beyond about x2. That
isn't too important, as speech that fast isn't awfully useful.

I find for the majority of TV, x1.5 is far too slow to be comfortable. :-)

Steve

[glen herrmannsfeldt]

Dave Platt wrote:

(snip)

Some of the TV networks are speeding up syndicated reruns by using
this sort of technique. They appear to be using the "chop out audio
samples" method to speed up the dialog (without pitch-shifting it) and
dropping out complete frames of the video. This works fairly well
when watching scenes with little action, but causes an odd
stuttering-jerk effect when the camera pans or somebody walks across
the screen.

I have a VCR that will play back at 1.5X without pitch shifting.
At higher playback speeds at only gives you part of the sound.
Maybe two second pieces with gaps depending on the speed.

The 1.5X playback is just a little too fast to watch a show
comfortably.

-- glen

[Arny Krueger]

"Don Pearce" wrote in message
...
On Mon, 20 Aug 2007 16:29:46 -0800, (Floyd L.
Davidson) wrote:

Scott Seidman wrote:
(Floyd L. Davidson) wrote in
:

Sheesh! That *is*, by definition a digital signal.


Funny, that's just what my D/A converters put out, and the spec sheets
claim they're putting out analog signals. Perhaps I should return them.

Your D/A converter puts out what is called
"quasi-analog". It's actually a digital PAM signal, not
an analog signal.

Whatever good DAs put out, it is good enough analog to fool my scope!

You can easily make it is a close approximation of the
original (with quantization distortion added), however,

But once you do that (by sending it through almost any
kind of an analog channel) it truly becomes "analog", in
the sense that you can no longer recover information or
use it as a digital signal.

This just goes on getting funnier by the post.

Yet another *eggspurt* who has never looked at the output of a good DAC with
a scope.

[Arny Krueger]

"Floyd L. Davidson" wrote in message
...
(Don Pearce) wrote:

Well, analog amplifiers generally have upper limits for frequencies
that they will pass.

Actually, they all do.

There's all sorts of phase distortion which
occurs when the frequency response drops off.

Usually, its pretty simple.

That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.

Nope, the output of good DAC is generally even more severely band-limited
than that of a good amplifier. That's why they call the filtering in DACs
"brick wall filters".

[Floyd L. Davidson]

Don Bowey wrote:
On 8/20/07 10:31 PM, in article , "Floyd L.
Davidson" wrote:

There simply are no such things as "analog repeaters"
on local telephone loops.

Since when?

Oh, perhaps 1950, maybe a few as late as 1960 or so...

Do you know of any telco that actually uses them today?

If a loop is long enough, and there is no pair-gain facility available, it
gets an "E" type repeater. If that isn't an analog repeater nothing is.

Of course I suppose it is possible they are still being
used where *you* live. But I don't know of any telco in
all of Alaska that has used an E repeater in the last 30-40
years. In particular, in the last 10-20 years that would
be totally unacceptable.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Jerry Avins]

Floyd L. Davidson wrote:
(Don Pearce) wrote:

...

You have cited a source that is describing something else. It is a

Bull**** Don, that is abjectly stupid to claim.

source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat
that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.

Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.

So, quantization error is the reason one has to sample faster than the
Nyquist rate! If you believe that, there's a bridge I want to sell you.

...

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Floyd L. Davidson]

(Don Pearce) wrote:
On Mon, 20 Aug 2007 22:14:45 -0800, (Floyd L.
Davidson) wrote:

source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat

Hmmm... says "Nyquist rate" right there.

that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.

Nyquist rate:

Hmmm... so that's exactly what I looked at.

The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.

Apparently *you* don't understand it. What they say is
correct. If you think otherwise, be my guest...

Actually I was talking about this:

You don't say? Why didn't you mention before what you
were talkiing about?

Nyquist's theorem: A theorem, developed by H. Nyquist, which states
that an analog signal waveform may be uniquely reconstructed, without
error, from samples taken at equal time intervals. The sampling rate
must be equal to, or greater than, twice the highest frequency
component in the analog signal. Synonym sampling theorem.

Go ahead and defend.

Claude Shannon proved it mathematically in the late
1940's.

You are free to dispute Shannon...

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Jerry Avins]

Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the output of a good DAC with
a scope.

Scope? SCOPE? isn't that an analog device? True digital work is don with
pencil, paper, and calculator. Theory rules!

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Floyd L. Davidson]

(Don Pearce) wrote:
On Mon, 20 Aug 2007 22:36:22 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:


A "quantized analogue signal" is digital by definition.


No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.

It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Well, analog amplifiers generally have upper limits for frequencies
that they will pass. There's all sorts of phase distortion which
occurs when the frequency response drops off. That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.


Bull****. Unless of course you are claiming that all digital signals
have perfectly flat tops and vertical edges. Is that your claim,
Floyd? You are no longer waving, but drowning. Just admit you have
this all wrong and bow out with as much grace as you can manage.

Phase may not affect your ears much, but it does affect
the data. It has nothing to do with flat tops and
vertical edges, which seem to be something you can't get
around.

I know you don't understand that, but everything else seems hard
for you too.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

If you think about the above for awhile, you're in for a big
surprise.

All of a sudden he has no answer. Come on Floyd - it is your claim
that an amplifier is a D to A converter. Now put up or shut up. Defend
it or admit you have screwed up.

My point is that there is a lot more to a practical
amplifier than just simple gain. Sorry that you missed
the point, again.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

"Arny Krueger" wrote:
"Floyd L. Davidson" wrote in message
...
(Don Pearce) wrote:

Well, analog amplifiers generally have upper limits for frequencies
that they will pass.

Actually, they all do.

However, if the upper limit is more than 2 or 3 times
higher than the frequency spectrum of the signal, in
effect they don't.

The point is we are *not* talking about wideband
amplifiers and narrow band signals, we are talking about
practical applications where the two are very closely
matched.

There's all sorts of phase distortion which
occurs when the frequency response drops off.

Usually, its pretty simple.

Sure it is... That's why there are complete books
published on what happens?

That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.

Nope, the output of good DAC is generally even more severely band-limited

Limited by the sampling rate.

than that of a good amplifier. That's why they call the filtering in DACs
"brick wall filters".

That is to prevent aliasing though, and is actually a
higher frequency cutoff than what is required to affect
the resulting output. And they are used on the *input*,
not on the output.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

"Arny Krueger" wrote:
"Don Pearce" wrote in message
...
On Mon, 20 Aug 2007 16:29:46 -0800, (Floyd L.
Davidson) wrote:

Scott Seidman wrote:
(Floyd L. Davidson) wrote in
:

Sheesh! That *is*, by definition a digital signal.


Funny, that's just what my D/A converters put out, and the spec sheets
claim they're putting out analog signals. Perhaps I should return them.

Your D/A converter puts out what is called
"quasi-analog". It's actually a digital PAM signal, not
an analog signal.

Whatever good DAs put out, it is good enough analog to fool my scope!

Your scope tells you if it is digital or analog information
on the display???? Wow, where do you find one like that?

Hint: you don't, because it can't.

You can easily make it is a close approximation of the
original (with quantization distortion added), however,

But once you do that (by sending it through almost any
kind of an analog channel) it truly becomes "analog", in
the sense that you can no longer recover information or
use it as a digital signal.

This just goes on getting funnier by the post.

Yet another *eggspurt* who has never looked at the output of a good DAC with
a scope.

Toss your old tube type Heathkit scope in the dumpster.
Get a good one, and sync it to the sampling clock.

Regardless, the idea that you think looking at a signal
with a scope will tell you if it is digital or analog
suggests that you weren't paying attention when you
studied basic signal theory, if you ever did.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Andor]

Jerry Avins wrote:
Floyd L. Davidson wrote:
....
Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.

So, quantization error is the reason one has to sample faster than the
Nyquist rate! If you believe that, there's a bridge I want to sell you.

Indeed.

On another note, I just read Shannon's "Communication in the presence
of noise" paper the other day. He does call the critial interval
between two sampling instants the Nyquist interval:

"Nyquist pointed out the fundamental importance of the time interval
1/2 W seconds in connection with telegraphy, and we will call this the
Nyquist interval corresponding to the band W."

This would mean that the Nyquist frequency, being the inverse of the
Nyquist interval, is the sampling frequency. However, I've never seen
the name used that way. Typically, the Nyquist frequency denotes
_half_ the sampling frequency. If anything, nomenclature will be the
end of this newsgroup.

Regards,
Andor

[Floyd L. Davidson]

Jerry Avins wrote:
Floyd L. Davidson wrote:
(Don Pearce) wrote:

...

You have cited a source that is describing something else. It is a
Bull**** Don, that is abjectly stupid to claim.

source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat
that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.
Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.

So, quantization error is the reason one has to sample
faster than the Nyquist rate! If you believe that,
there's a bridge I want to sell you.

If you don't understand what they said, you probably do
have a bridge that somebody sold you...

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.

Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Bob Myers]

"Floyd L. Davidson" wrote in message
...


"Analog" != "continuous," even though most commonly
"analog" signals are also continuous in nature.

Analog signals are by *definition* continous.

Nonsense. You don't believe it is possible to sample
an "analog" signal and have it remain analog?

You have misunderstood what that means though. The
analog value of a signal is continuous,

Well, THAT certainly makes it clearer....

Since you seem to be so hung up on definitions, Floyd,
try this one on for size:

Continuous: unchanged or uninterrupted: continuing
without changing, stopping, or being interrupted in space
or time.

Note that this does not say anything at all about the range
of possible values being "continuous" (which is what you
seem to be trying to say in the above).

Bob M.

[Arny Krueger]

"Floyd L. Davidson" wrote in message
...
"Arny Krueger" wrote:
"Don Pearce" wrote in message
...
On Mon, 20 Aug 2007 16:29:46 -0800, (Floyd L.
Davidson) wrote:

Scott Seidman wrote:
(Floyd L. Davidson) wrote in
:

Sheesh! That *is*, by definition a digital signal.


Funny, that's just what my D/A converters put out, and the spec sheets
claim they're putting out analog signals. Perhaps I should return
them.

Your D/A converter puts out what is called
"quasi-analog". It's actually a digital PAM signal, not
an analog signal.

Whatever good DAs put out, it is good enough analog to fool my scope!

Your scope tells you if it is digital or analog information
on the display???? Wow, where do you find one like that?

Hint: you don't, because it can't.

You can easily make it is a close approximation of the
original (with quantization distortion added), however,

But once you do that (by sending it through almost any
kind of an analog channel) it truly becomes "analog", in
the sense that you can no longer recover information or
use it as a digital signal.

This just goes on getting funnier by the post.

Yet another *eggspurt* who has never looked at the output of a good DAC
with
a scope.

Toss your old tube type Heathkit scope in the dumpster.

Never had one.

Get a good one, and sync it to the sampling clock.

Been there, done that.

Regardless, the idea that you think looking at a signal
with a scope will tell you if it is digital or analog
suggests that you weren't paying attention when you
studied basic signal theory, if you ever did.

I aced "Signals And Systems Analysis" and placed high in "Linear Stochastic
Optimal Control" - probably the heaviest signals trips I ever took.

[Bob Myers]

"glen herrmannsfeldt" wrote in message
. ..
There needs to be a way to describe sampled but not quantized
signals. They are not continuous in time, but the function
can take on any value at each sample point.

Such signals are simply referred to as "sampled."
Whether the data they carry is encoded in "digital"
or "analog" form is a separate question.

The value that any symbol has (to use the proper
communications or information theory term) is
ALWAYS limited in accuracy/resolution, regardless
of the encoding system used. There is no such thing
as an information encoding system or communications
channel which provides "infinite" accuracy/resolution,
therefore to say that a signal can take on "any"
value becomes to a large extent meaningless.

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...


If you quantize the magnitude, it is digital. That is
by definition.
No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

Really? Suppose I show you an oscilloscope screen which
is displaying a single line of video, which happens to be
carrying an 8-level gray-scale pattern. It clearly shows
a set of discrete levels. Further, since this video happened
to be created by a D/A converter with only three bits at
the input (our video generator was built on the cheap!), those
are the ONLY levels this signal may exhibit. Is this a
"digital" signal?

Bull**** son. Look it up. I've provided you with
quotes from an authoritative reference, twice now. You
don't have to take my word for it, that *is* the agreed
technical definition of the term.

Ah, Floyd - argument from authority again, huh?

Bob M.

[Arny Krueger]

"Floyd L. Davidson" wrote in message
...
"Arny Krueger" wrote:
"Floyd L. Davidson" wrote in message
...
(Don Pearce) wrote:

Well, analog amplifiers generally have upper limits for frequencies
that they will pass.

Actually, they all do.

However, if the upper limit is more than 2 or 3 times
higher than the frequency spectrum of the signal, in
effect they don't.

Nope, the phase shift is appreciable down to Fc/10. Ever hear of Bode plots?

The point is we are *not* talking about wideband
amplifiers and narrow band signals, we are talking about
practical applications where the two are very closely
matched.

Most digital audio is brick walled at 0.95 * Fs/2 or about 21 KHz. Most
power amps are pretty flat up to about 50 KHz.

There's all sorts of phase distortion which
occurs when the frequency response drops off.

Usually, its pretty simple.

Sure it is... That's why there are complete books
published on what happens?

For people who don't already know?

That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.

Nope, the output of good DAC is generally even more severely band-limited

Limited by the sampling rate.

Well, by the brick wall filter which is usually set as stated above.

than that of a good amplifier. That's why they call the filtering in DACs
"brick wall filters".

That is to prevent aliasing though,

DACs can't alias. Only ADCs can alias. Improperly filtered DACs may produce
images.

and is actually a
higher frequency cutoff than what is required to affect
the resulting output. And they are used on the *input*,
not on the output.

The input side of a digital system is called an ADC, not a DAC as you just
said.

[Arny Krueger]

"Floyd L. Davidson" wrote in message
...
Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.

Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

(1) A decent scope gives a pretty close approximation of what theory
predicts.

(2) I was probably working with decent scopes before you were born.

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

I've seen both kinds of data many times. Imaging data almost never looks
like sine waves.