On Wed, 7 Sep 2005 08:52:25 +1200, Geoff@work wrote:

"Don Pearce" wrote in message
news:1mee4n3x98z25.dv0phtyzvns3

Didn't they just? But there was obviously some puss left in the boil.


Trouble is, without a course of antibiotics ( and increasingly even *with*),
boils just keep popping up everywhere...

geoff

Wouldn't the world be so much better if people could be born as adults -
then we wouldn't have to suffer teenagers.

d

On 9/7/05 2:31 AM, in article ,
"Don Pearce" wrote:

On Wed, 7 Sep 2005 08:52:25 +1200, Geoff@work wrote:

"Don Pearce" wrote in message
news:1mee4n3x98z25.dv0phtyzvns3

Didn't they just? But there was obviously some puss left in the boil.


Trouble is, without a course of antibiotics ( and increasingly even *with*),
boils just keep popping up everywhere...

geoff

Wouldn't the world be so much better if people could be born as adults -
then we wouldn't have to suffer teenagers.

Adults are just children that managed to stay alive long enough to get
rights.

"Don Pearce" wrote in message
...
On Wed, 7 Sep 2005 08:52:25 +1200, Geoff@work wrote:

"Don Pearce" wrote in message
news:1mee4n3x98z25.dv0phtyzvns3

Didn't they just? But there was obviously some puss left in the boil.


Trouble is, without a course of antibiotics ( and increasingly even
*with*),
boils just keep popping up everywhere...

geoff

Wouldn't the world be so much better if people could be born as adults -
then we wouldn't have to suffer teenagers.


There was an adult doctor, pateient and nurse. One day the doctor was
alarmed to hear frantic screamimg coming from the surgery. He rushed in and
yelled to the nurse holding a kettle "No No No - I asked you to PRICK his
BOIL !"

geoff

Timo Haanpää writes:

See http://en.wikipedia.org/wiki/Reconstruction_filter

Actually this page contains a glaring error: a reconstruction filter
is NOT used to avoid "aliasing" in a DAC, and goes to show why folks
shouldn't trust what is written on the web too readily.
--
% Randy Yates % "And all that I can do
%% Fuquay-Varina, NC % is say I'm sorry,
%%% 919-577-9882 % that's the way it goes..."
%%%% % Getting To The Point', *Balance of Power*, ELO
http://home.earthlink.net/~yatescr

Randy Yates wrote:

Timo Haanpää writes:

See http://en.wikipedia.org/wiki/Reconstruction_filter

Actually this page contains a glaring error: a reconstruction filter
is NOT used to avoid "aliasing" in a DAC, and goes to show why folks
shouldn't trust what is written on the web too readily.

My understanding was the information theorists' preferred name for the filter after
a DAC was *anti-imaging* - not anti-aliasing.

An *anti-aliasing* filter is used prior to the ADC.

The anti-aliasing filter is used prior to the ADC to stop frequencies in the input
signal that are above the Nyquist frequency from creating 'false samples' or
'aliases'.

The anti-imaging filter stops the high frequency content at the DAC output from
creating an 'ultrasonic image' of the audio band signal.

Both filters may be very similar. The end result of the job they are doing is rather
different.

Graham

Randy Yates kirjoitti:
Actually this page contains a glaring error: a reconstruction filter
is NOT used to avoid "aliasing" in a DAC, and goes to show why folks
shouldn't trust what is written on the web too readily.

Yeah, I noticed that, too, but I reckoned it was still understandable.

Timo

In article , says...

Timo Haanpää writes:

See http://en.wikipedia.org/wiki/Reconstruction_filter

Actually this page contains a glaring error: a reconstruction filter
is NOT used to avoid "aliasing" in a DAC, and goes to show why folks
shouldn't trust what is written on the web too readily.


Because of the way Wikipedia works, it is one of the most reliable resources on
the web. If you find an error, edit the page or mention it in the discussion
page so that someone else can correct it. Pointing to it here as some kind of
triumph is useless and indicates that you don't understand the purpose and
process of Wikipedia.

"Chevdo" wrote in message news:Y0TTe.228940
Because of the way Wikipedia works, it is one of the most reliable
resources on
the web. If you find an error, edit the page or mention it in the
discussion
page so that someone else can correct it. Pointing to it here as some
kind of
triumph is useless and indicates that you don't understand the purpose and
process of Wikipedia.

So if enough people agree that something wrong is right, it becomes right ?

geoff

In article , says...


"Chevdo" wrote in message news:Y0TTe.228940
Because of the way Wikipedia works, it is one of the most reliable
resources on
the web. If you find an error, edit the page or mention it in the
discussion
page so that someone else can correct it. Pointing to it here as some
kind of
triumph is useless and indicates that you don't understand the purpose and
process of Wikipedia.

So if enough people agree that something wrong is right, it becomes right ?

No, it remains wrong until someone corrects it. But, before correcting
anything, it's standard practice to discuss it on the dicussion page with
others who consider themselves knowledgable enough on the subject to
participate usefully in the discussion, to see what kind of correction would be
most appropriately condusive to a consensus of clarity.

In article LVVTe.232374$tt5.40343@edtnps90, says...

In article , says...


"Chevdo" wrote in message news:Y0TTe.228940
Because of the way Wikipedia works, it is one of the most reliable
resources on
the web. If you find an error, edit the page or mention it in the
discussion
page so that someone else can correct it. Pointing to it here as some
kind of
triumph is useless and indicates that you don't understand the purpose and
process of Wikipedia.

So if enough people agree that something wrong is right, it becomes right ?

No, it remains wrong until someone corrects it. But, before correcting
anything, it's standard practice to discuss it on the dicussion page with
others who consider themselves knowledgable enough on the subject to
participate usefully in the discussion, to see what kind of correction would
be
most appropriately condusive to a consensus of clarity.



By the way, pages covering controversial topics, which are most likely to
contain errors, are accompanied by disclaimers informing the reader of the
'disputed neutrality' of the article. Technical pages don't usually cause
people to abandon their neutrality like ideological ones do.

"Pooh Bear" wrote
in message
Randy Yates wrote:

Timo Haanpää writes:

See http://en.wikipedia.org/wiki/Reconstruction_filter

Actually this page contains a glaring error: a
reconstruction filter is NOT used to avoid "aliasing" in
a DAC, and goes to show why folks shouldn't trust what
is written on the web too readily.

My understanding was the information theorists' preferred
name for the filter after a DAC was *anti-imaging* - not
anti-aliasing.

Is there really a lot of difference between the two phrases?

Isn't an image a kind of alias?

An *anti-aliasing* filter is used prior to the ADC.

Agreed.

The anti-aliasing filter is used prior to the ADC to stop
frequencies in the input signal that are above the
Nyquist frequency from creating 'false samples' or
'aliases'.

Agreed.

The anti-imaging filter stops the high frequency content
at the DAC output from creating an 'ultrasonic image' of
the audio band signal.

Aren't the images conceptually similar to the aliases that
we worry about in the ADC?

Both filters may be very similar. The end result of the
job they are doing is rather different.

Kinda like mirror images, just like most of the the other
functions of the respective converters.

The inbound filter reduces garbage response to image
frequencies, the output filter reduces garbage output at
image frequencies.

The anti-imaging filter stops the high frequency content
at the DAC output from creating an 'ultrasonic image' of
the audio band signal.

Aren't the images conceptually similar to the aliases that
we worry about in the ADC?

Well... Not really. The images appear outside the frequency range of
interest, not within it.

The anti-aliasing filter is absolutely required (if the signal contains
components above twice the sampling frequency, which is usually the case).

But the anti-imaging filter is needed only because the amps and speakers
down the line can't handle the ultrasonic "junk". If the amps and speakers
were perfect, the anti-imaging filter wouldn't be needed.

On Thu, 8 Sep 2005 15:54:23 -0700, "William Sommerwerck"
wrote:

The anti-aliasing filter is absolutely required (if the signal contains
components above twice the sampling frequency, which is usually the case).

But the anti-imaging filter is needed only because the amps and speakers
down the line can't handle the ultrasonic "junk". If the amps and speakers
were perfect, the anti-imaging filter wouldn't be needed.

But, but, but, aren't the images just exactly as large
as the passband/ desired signal? Why wouldn't this be
important?

Perfection is reserved for heaven:

"And when there's nothing to want
when we're all brilliant and fast
when all tomorrows are gone
there will be teeth in the grass."
-iron and wine, _our endless numbered days_, 2004

Thanks, as always,

Chris Hornbeck

William Sommerwerck wrote:

snip

But the anti-imaging filter is needed only because the amps and speakers
down the line can't handle the ultrasonic "junk". If the amps and speakers
were perfect, the anti-imaging filter wouldn't be needed.

I don't understand how out-of-band frequencies that are (I think) only
nominally correlated to signals' in-band frequencies would be acceptable
if they could be perfectly reproduced. I willing to be taught, though!

--
================================================== ======================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
mrkesti at comcast dot net | - The Who, Bargain

Michael R. Kesti wrote:
William Sommerwerck wrote:

But the anti-imaging filter is needed only because the amps and speakers
down the line can't handle the ultrasonic "junk". If the amps and speakers
were perfect, the anti-imaging filter wouldn't be needed.

I don't understand how out-of-band frequencies that are (I think) only
nominally correlated to signals' in-band frequencies would be acceptable
if they could be perfectly reproduced. I willing to be taught, though!

IF they could be perfectly reproduced, then there would be no distortion
products resulting from them.

AND if they were completely inaudible themselves, then they would make
no difference in the sound.

The only thing you'd lose would be some headroom, spent producing sound
that would be wasted. Admittedly that's an annoyance.

It's academic, anyway, since you can't move air back and forth with
infinite speed.
--scott

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

On Thu, 08 Sep 2005 23:09:43 GMT, Chris Hornbeck
wrote:

But, but, but,

"But me no buts". Apologies to the much earlier
William S. but! I've just discovered a movie that
flew sadly under my radar. _Stage Beauty_ is
set in the 1660's and incorporates play within a
play structure, but is also broader and deeper.

It's from Richard Eyre, so it has some (the best
parts only, IMO) of BBC production values, including
all of the cast except the two American leads,
who each do their own best-to-date work here.)

It's sorta-kinda a British version of _Shakespeare
in Love_, (which was great!), but without the Hollywood.
Well, not really even a good comparison.

Sorry for the Insurrection. Now returning you to the
channel of yer choice...

Chris Hornbeck

(Chevdo) writes:

In article , says...

Timo Haanpää writes:

See http://en.wikipedia.org/wiki/Reconstruction_filter

Actually this page contains a glaring error: a reconstruction filter
is NOT used to avoid "aliasing" in a DAC, and goes to show why folks
shouldn't trust what is written on the web too readily.


Because of the way Wikipedia works, it is one of the most reliable resources on
the web. If you find an error, edit the page or mention it in the discussion
page so that someone else can correct it. Pointing to it here as some kind of
triumph is useless and indicates that you don't understand the purpose and
process of Wikipedia.

I don't share your respect of the Wikipedia system.

I emailed several months ago on the error in this definition, as well
as several other folks from the comp.dsp newsgroup. The error still
persists. I have editing ability on that definition, but there is a
disclaimer that your edits are subject to being changed by others, so
what's the use?

You state that there is a sort of review system by those who consider
themselves knowledgeable in the area. Since when is one's evaluation
of one's own competence a reliable indicator of true competence?

In a published book, there is much more at stake (e.g., the
publisher's reputation, the author's reputation, and both of their
financial gains) and so they tend to be much more careful, in my
opinion.

Wikopedia can be useful, but the user must beware.
--
% Randy Yates % "And all that I can do
%% Fuquay-Varina, NC % is say I'm sorry,
%%% 919-577-9882 % that's the way it goes..."
%%%% % Getting To The Point', *Balance of Power*, ELO
http://home.earthlink.net/~yatescr

On Fri, 09 Sep 2005 02:25:15 GMT, Randy Yates wrote:

You state that there is a sort of review system by those who consider
themselves knowledgeable in the area. Since when is one's evaluation
of one's own competence a reliable indicator of true competence?

"Four legs good; two legs bad."

In a published book, there is much more at stake (e.g., the
publisher's reputation, the author's reputation, and both of their
financial gains) and so they tend to be much more careful, in my
opinion.

Books have editors. A newsgroup *almost* has editors,
but only the better ones. Newsgroups without a consensus
"editor" viewpoint fall into chaos and die, choking.

I admire the hippy ethos of Wiki-stuff, but there're
good practical resons why free love and free thought
no longer exist; some harsh.

And I also wish the Wiki team all the best; it's a
great concept. The issue of concensus editing is tricky
but could possibly be done.

Wait, I'm wrong, these kids are so much smarter than me
that I can confidently say that it *can* be done.

Chris Hornbeck
"But it's the almostness of Godard's films that makes it special;
if it were too perfect, it would be mechanized and dull. Instead
of dancing, it would be choreography, an applied science."
-rcraig62 commenting on _Bande a part_, 1964

Geoff Wood wrote:

"Chevdo" wrote in message news:Y0TTe.228940

Because of the way Wikipedia works, it is one of the most reliable
resources on
the web. If you find an error, edit the page or mention it in the
discussion
page so that someone else can correct it. Pointing to it here as some
kind of
triumph is useless and indicates that you don't understand the purpose and
process of Wikipedia.


So if enough people agree that something wrong is right, it becomes right ?

geoff



No. Somebody comes along, in a Cecil Adams sort of way, and
provides vetted data to support their version.

--
Les Cargill

In article , says...

I don't share your respect of the Wikipedia system.

I emailed several months ago on the error in this definition, as well
as several other folks from the comp.dsp newsgroup. The error still
persists. I have editing ability on that definition, but there is a
disclaimer that your edits are subject to being changed by others, so
what's the use?

You state that there is a sort of review system by those who consider
themselves knowledgeable in the area. Since when is one's evaluation
of one's own competence a reliable indicator of true competence?


Your second paragraph seems to contradict your opinion in the first paragraph
where you state that your edits should be accepted because you say so. If your
edits are being rejected, why don't you ask on the discussion page why that
keeps happening? I guess we'll just have to suffer with an error on that page
until you or somebody else figures out a way to get it corrected, (assuming
there is an error at all, and your edits aren't being rejected because they
don't offer any additional clarity).


In a published book, there is much more at stake (e.g., the
publisher's reputation, the author's reputation, and both of their
financial gains) and so they tend to be much more careful, in my
opinion.

Well that's ridiculous. The most popular books are fiction, even the ones on
the non-fiction best-sellers lists. How many books are there on UFO
visitation, tarot card reading, astrology, bible codes, etc? With Wikipedia
you will get a fair analysis of those subjects and any others.


Wikopedia can be useful, but the user must beware.

Yes, and the open nature of Wikipedia assures the user that he will see
everything that is going on, in other words, it is the one major medium in
existence where the user gets to beware most. The only people who give a crap
about 'reputation' are those who's reputation is controversial. For example,
Jon Atkinson would like you to believe that he and his magazine have a
reputation for high credibility, even though they've been ridiculed by the JREF
for writing positive reviews of magic tone-sweetening stereo stones, and
defending those reviews when confronted. Stereophile magazine now has all the
credibility of a spoon-bending psychic. Yet they still have subscribers and
readers who either aren't aware of Stereophile's bad reputation, or who want to
believe in the magic stones, too.

In article w89Ue.261903$on1.150679@clgrps13, says...

Well that's ridiculous. The most popular books are fiction, even the ones on
the non-fiction best-sellers lists. How many books are there on UFO
visitation, tarot card reading, astrology, bible codes, etc? With Wikipedia
you will get a fair analysis of those subjects and any others.



By the way, the two most popular books in existence, Harry Potter and the
bible, are fairy tales depicting supernatural events. And in the case of the
bible, they are even presented as historical fact! There's not a major
publishing house on the planet that doesn't have a piece of the flummery
action, they've all got horoscope books, UFO books, etc. They don't seem to be
too concerned about their reputation, maybe because they're laffing all the way
to the bank?

Scott Dorsey kirjoitti:
IF they could be perfectly reproduced, then there would be no distortion
products resulting from them.

Wouldn't you get amplitude modulation near Nyquist frequency if the
output wasn't filtered? Or am I missing something (showing my
stupidity)?

Timo

"Timo Haanpää" wrote in message

Scott Dorsey kirjoitti:

IF they could be perfectly reproduced, then there would
be no distortion products resulting from them.

Wouldn't you get amplitude modulation near Nyquist
frequency if the output wasn't filtered?

No, you just get the spurious responses above the Nyquist
frequency.

What does happen along a similar line is that tone bursts
have distorted envelopes near the corner frequency of the
low pass filter.

"Chevdo" wrote in message news:LVVTe.232374


So if enough people agree that something wrong is right, it becomes right
?

No, it remains wrong until someone corrects it.

Or remains right until somebody incorrects it ! Presumably then somebody
else who care may re-correct it, buut that's unfortunate if you gather the
info in the meantime....


geoff