Class/type of amp ?

[William Sommerwerck]

However one quibble: simply chopping the time stream up into integral
slices and restricting the level (or width [or frequency {or phase}]) of
an output signal to specific levels does not "really" 'digitize' the data.
Doing an analogue to digital conversion and transmitting the data in the
form of a stream of digitized information (as opposed to one out of 1024
possible levels, for example) is essential in order for the information to
be 'digital' [in my mind].

This arbument has come up before. Some people think that the quantized data
must be represted as a "number" in order to be truly digital. Am moment's
thought will show this is not so.

The "number of bits" is determined by the number of levels. Indeed, we could
quantize at non-binary increments, if we wanted, and the data would still be
"digital".

In any case, it has been an interesting discussion to follow. Thank you
BOTH.

You're welcome. Thank you for reading and thinking.

 

[William Sommerwerck]

William Sommerwerck wrote:

There are no other classes. To call switching amps "class D", or to
create
new designations for stepped B+ or stepped-bias designs thoroughly
confuses
the original meaning.

So what would you call them ?

I wouldn't call them "classes", just a name describing how they work or what
they do.

As soon as you start giving design concepts fancy names,
every manufacturer will pick his own, and no one will know
quite where they are at ...

They'll do it anyhow, for marketing. If Hitachi has a class-G amplifier,
then Toshiba, even though using the same circuit, will call it class H,
simply to look original.

WRONG. Class G and H use quite different circuits.

They might be true, but that wasn't the point I was making. There is such a
thing as "product differentiation", and you don't make yourself look
different by appearing to copy someone else's feature.

 

[Arfa Daily]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:gig2ai$l71$1@news.motzarella.org...

The Web is wrong. Most switching amps are analog. That is,
everything varies continuously, rather than in quantized steps.

That is a confusing and not particularly true statement.

It might be confusing if you've been brainwashed into thinking "pulses" =
"digital", but it is nevertheless true.


By the way, Arfa, you're doing something intellectually invalid --
you're
"appealing to authority", rather than thinking for yourself, or
explaining
what's going on.

I am not.

Then why did you post Web references as examples of what other people
think?
Majority opinion is proof of nothing.


Because on average, in the real world, if "millions of people" believe
something, and one does not, it is not the millions who actually *are*
wrong.

On average. But there are exceptions. The world is not 6000 years old. Yet
millions of people believe that. The majority is not the "authority".

Oh puh - leees ...

I'm not really quite sure exactly what you're saying here about the class
D
amplifier. The analogue input signal is not converted directly to any
kind
of 'value' represented by a binary number, such as might be the case if
you ran it through a traditional A-D converter. Instead, it is run
through
a
comparator, with a triangle wave as the reference input. This results in
direct conversion to a PWM signal. I accept that this does not represent
'quantization' as such, so is not producing a "truly digital" signal, but
I
also do not believe that once the signal is in PWM form, it can either be
considered to be analogue any more.

Ah! Here's the problem. It's the confusion between /waveform/ and /data/.

A pulse is just a pulse. In and of itself it means nothing. It is neither
"digital" nor "analog" -- it's just a waveform.

The issue here is how we modify a waveform to transmit data.

Suppose we sampled a signal at or above the Nyquist rate and transmitted
each sampled value as a pulse of that value. (This is easily done with a
sample-and-hold circuit.)

How is the /data/ in that series of pulses represented? Well, it varies
/continuously/, just as the original signal did. It has not been
quantized,
so it cannot be represented as one of a /finite/ group of numbers. That's
analog -- continuous variation.

OK. I understand why you might contend that a PWM signal is an alternative
analogue version of the original (conventionally understood) analogue
signal. However, I still believe that calling a class D amplifier
"analogue", and insisting that it is not in any way 'digital' is likely to
be confusing to the vast majority of conventionally schooled electronic
service engineers, as opposed to those who have sufficient understanding and
interest in the math of signal digitization and processing to feel
otherwise.

Rightly or wrongly, most service engineers understand an analogue signal as
what you would conventionally see on a 'scope, if you put it across an
amplifier's speaker terminals, whereas a signal that varies between two
levels only, irrespective of how the pulse width is varying, tends to be
considered as digital, due to the 'conventional' understanding that simple
service engineers have, of the operation of logic circuits (as for ECL, that
was a special case that most will never have heard of anyway, and as I
recall, the 'pulses' were nothing like a sine wave, and actually difficult
to distinguish from the noise floor).

As far as my quoting web references goes, most normal people consider this
resource to be the repository of all human knowledge, and the dog's bollocks
of reference media. Whilst it is of course not always right on everything,
where there is collected opinion from many many different and respected
sources, and that opinion is broadly consistent, surely any reasonable
person could not be considered stupid, or without thought of their own, for
accepting it as a lesson. How else do we learn about any subject other than
to either research it, or be taught it by someone considerd to be an expert
? Thus, I make no apology for using the 'net as a research tool, and for
citing links to the data I have found.

I still contend that there is no real name for the process employed in a
class D amplifier. I don't believe that it is analogue in the conventionally
understood sense (and I really don't care if you and bz feel that makes me
"mistook" was it he called me ?) and if you want to be purist about the math
of quantization, neither is it digital in the true sense.

Perhaps we need to coin a new name for it. As it's similar in concept to a
switch mode power supply, maybe we should call it a 'switch mode amplifier'.

And that really is all the time that I want to waste on this. I know what I
mean, and I rather think that most conventional engineers on here do too,
and understand quite well what is implied when calling a class D amplifier,
digital ...

Arfa

<snip rest>

 

[William Sommerwerck]

OK. I understand why you might contend that a PWM signal is an alternative
analogue version of the original (conventionally understood) analogue
signal. However, I still believe that calling a class D amplifier
"analogue", and insisting that it is not in any way 'digital' is likely to
be confusing to the vast majority of conventionally schooled electronic
service engineers, as opposed to those who have sufficient understanding
and
interest in the math of signal digitization and processing to feel
otherwise.

I've known some pretty bright service technicians. In fact, one of them is
one of the most-intelligent and best-educated people I've ever known. Why
should I patronize them by assuming they can't understand?

As far as my quoting web references goes, most normal people consider this
resource to be the repository of all human knowledge, and the dog's
bollocks
of reference media. Whilst it is of course not always right on everything,
where there is collected opinion from many many different and respected
sources, and that opinion is broadly consistent, surely any reasonable
person could not be considered stupid, or without thought of their own,
for
accepting it as a lesson. How else do we learn about any subject other
than
to either research it, or be taught it by someone considerd to be an
expert
? Thus, I make no apology for using the 'net as a research tool, and for
citing links to the data I have found.

I use the Web as a research tool, and often refer to (and correct!)
Wikipedia. But I don't assume that because somethingt is on the Web or in
Wikipedia, it's necessarily true.
'

I still contend that there is no real name for the process employed
in a class D amplifier.

There is. It's (usually) analog pulse-width modulation.

Perhaps we need to coin a new name for it. As it's similar in concept to a
switch mode power supply, maybe we should call it a 'switch mode
amplifier'.

Nothing wrong with that.

 

[Eeyore]

William Sommerwerck wrote:

William Sommerwerck wrote:

There are no other classes. To call switching amps "class D", or to
create new designations for stepped B+ or stepped-bias designs thoroughly
confuses the original meaning.

So what would you call them ?

I wouldn't call them "classes", just a name describing how they work or what
they do.

That's why they're called a 'class' since everyone knows the output is AB.

As soon as you start giving design concepts fancy names,
every manufacturer will pick his own, and no one will know
quite where they are at ...

They'll do it anyhow, for marketing. If Hitachi has a class-G amplifier,
then Toshiba, even though using the same circuit, will call it class H,
simply to look original.

WRONG. Class G and H use quite different circuits.

They might be true, but that wasn't the point I was making. There is such a
thing as "product differentiation", and you don't make yourself look
different by appearing to copy someone else's feature.

Class G and H achieve similar results by different means. The distinction is
REAL not marketing.
http://en.wikipedia.org/wiki/Class_AB#Class_G_and_H

Graham

 

[bz]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in
news:C3Z2l.7364$T07.4948@newsfe09.ams2:

Again, I say that you are not wrong, in theory, but neither are you
right in practice, when referring to today's much-changed world of
electronics.

If one wants to understand a concept, one makes sure that they understand
how the words are being used.

Understanding what others mean when they use a certain word is important to
communications.

In many technical fields, 'common words' have 'uncommon definitions'.
This leads to a LOT of misunderstandings and has high costs, but it is
often useful and necessary.

A 'careful communicator' will try to find out what others mean when they
use specific words and tailor their communications to use the language of
the listener. Doing otherwise is as counter productive as walking into a
room full of people that only speak Etruscan and giving a lecture in Greek.

Arguing about what a word 'really means' is a waste of time and energy.

If one wants to communicate with others, one uses words that others
understand in the way that they understand them.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Eeyore]

Eeyore wrote:

William Sommerwerck wrote:
William Sommerwerck wrote:

There are no other classes. To call switching amps "class D", or to
create new designations for stepped B+ or stepped-bias designs thoroughly
confuses the original meaning.

So what would you call them ?

I wouldn't call them "classes", just a name describing how they work or what
they do.

That's why they're called a 'class' since everyone knows the output is AB.

You COULD call them AB + G or AB + H but since it's a bit of a mouthful most
people don't. Rail switching or modulating is a bit technical for the average
buyer.

Graham

 

[Arfa Daily]

"bz" <bz+ser@ch100-5.chem.lsu.edu> wrote in message
news:Xns9B79EFBEAF73BWQAHBGMXSZHVspammote@130.39.198.139...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in
news:C3Z2l.7364$T07.4948@newsfe09.ams2:

Again, I say that you are not wrong, in theory, but neither are you
right in practice, when referring to today's much-changed world of
electronics.


If one wants to understand a concept, one makes sure that they understand
how the words are being used.

Understanding what others mean when they use a certain word is important
to
communications.

In many technical fields, 'common words' have 'uncommon definitions'.
This leads to a LOT of misunderstandings and has high costs, but it is
often useful and necessary.

A 'careful communicator' will try to find out what others mean when they
use specific words and tailor their communications to use the language of
the listener. Doing otherwise is as counter productive as walking into a
room full of people that only speak Etruscan and giving a lecture in
Greek.

Arguing about what a word 'really means' is a waste of time and energy.

If one wants to communicate with others, one uses words that others
understand in the way that they understand them.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap0

So what exactly are you saying here ? That it's right to use the word
"digital" in it's modern context, which all service engineers world-wide
would understand, or not ? Each time I read thru' what you've said, I arrive
at an opposite conclusion !

I *try* to be a careful communicator always, allowing for the fact that
people who are not native English speakers, may well be reading, and also
that many Americans will be reading, who tend to use the language in a much
more 'literal' way than those of us in the UK. That difference, and the
difference in sense of humour, can easily lead to conflict, so I try to take
both of those factors into account when I do post.

Maybe I don't get it right all the time, but at least I do try ..

Arfa (dah-di-dah)

Arfa

 

[William Sommerwerck]

I wouldn't call them "classes", just a name describing
how they work or what they do.

That's why they're called a "class" since everyone knows the output is AB.

The word "class" has several meanings. One of them has an implication that
is different from "type". Class A -- conduction through the full cycle -- is
not called A by accident.

They might be true, but that wasn't the point I was making. There is
such a thing as "product differentiation", and you don't make yourself
look different by appearing to copy someone else's feature.

Class G and H achieve similar results by different means. The distinction
is REAL not marketing.

But that isn't the point. If company A used the same circuit as company B,
it would be foolish for them to use the same designation. That was the
point, not whether "class" G and "class" H are the same or different.

 

[Eeyore]

William Sommerwerck wrote:

I wouldn't call them "classes", just a name describing
how they work or what they do.

That's why they're called a "class" since everyone knows the output is AB.

The word "class" has several meanings. One of them has an implication that
is different from "type". Class A -- conduction through the full cycle -- is
not called A by accident.

That's a very restricted use applying only to A, B and C.

They might be true, but that wasn't the point I was making. There is
such a thing as "product differentiation", and you don't make yourself
look different by appearing to copy someone else's feature.

Class G and H achieve similar results by different means. The distinction
is REAL not marketing.

But that isn't the point. If company A used the same circuit

Do you mean 'topology' rather than circuit ?

as company B, it would be foolish for them to use the same designation.

But they DO ! Very many brands of Class G and H amps exist ! G or H describes
the method used to reduce dissipation in the output stage.

That was the point, not whether "class" G and "class" H are the same or
different.

I don't even begin to understand that statement, sorry.

Did you read the wikipedia link btw ?

Graham

 

[William Sommerwerck]

So what exactly are you saying here ? That it's right to use the word
"digital" in it's modern context, which all service engineers world-wide
would understand, or not ? Each time I read thru' what you've said, I
arrive
at an opposite conclusion !

I agree. This is a technical issue, not one of getting along with people
from a different society.

Arfa (dah-di-dah)

'K? <grin>

 

[William Sommerwerck]

There are no other classes. To call switching amps "class D", or to
create new designations for stepped B+ or stepped-bias designs
thoroughly confuses the original meaning [of classes].

So what would you call them ?

I wouldn't call them "classes", just a name describing how they work
or what they do.

That's why they're called a 'class' since everyone knows the output is
AB.

You COULD call them AB + G or AB + H but since it's a bit of a mouthful
most people don't. Rail switching or modulating is a bit technical for the
average buyer.

That's true, but if the average buyer doesn't have at least some minimal
understanding of how the circuit works, then the letter pretty much means
nothing -- other than as a way to distinguish to product, or (possibly)
impress him.

"Rail switching" is a good term. Here's a simple explanation for the
technically uninformed:

"A high-power amplifier requires a high voltage on its output stage. But the
higher the voltage, the hotter the amplifier runs. Because the highest
output power is rarely needed for more than a few seconds, this amplifier
uses a switched power supply, "cranking up" the voltage only when it's
needed. This lets the amplifier produce a lot of power without a lot of
expensive output transistors or huge heat sinks."

That's pretty good for a first draft.

 

[William Sommerwerck]

But that isn't the point. If company A used the same circuit

Do you mean 'topology' rather than circuit?

Yes.

Did you read the Wikipedia link BTW?

I browsed it. I agree that there is a meaningful difference between G and H.
(I would never buy an amplifer whose output-stage voltage varied in a large
number of steps. It bothers me, for reasons too complex to explain briefly.)

I also read the Class D section. The author does not describe Class D as
digital. He says...

"Class D amplifiers can be controlled by either analog or digital circuits.
The digital control introduces additional distortion called quantization
error caused by its conversion of the input signal to a digital value."

and

"The letter D used to designate this amplifier class is simply the next
letter after C, and does not stand for digital. Class D and Class E
amplifiers are sometimes mistakenly described as "digital" because the
output waveform superficially resembles a pulse-train of digital symbols,
but a Class D amplifier merely converts an input waveform into a
continuously pulse-width modulated (square wave) analog signal. (A digital
waveform would be pulse-code modulated.)"

Except for the last sentence, this is a correct statement.

 

[Arfa Daily]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:giit05$odq$1@news.motzarella.org...

But that isn't the point. If company A used the same circuit

Do you mean 'topology' rather than circuit?

Yes.


Did you read the Wikipedia link BTW?

I browsed it. I agree that there is a meaningful difference between G and
H.
(I would never buy an amplifer whose output-stage voltage varied in a
large
number of steps. It bothers me, for reasons too complex to explain
briefly.)

I also read the Class D section. The author does not describe Class D as
digital. He says...

"Class D amplifiers can be controlled by either analog or digital
circuits.
The digital control introduces additional distortion called quantization
error caused by its conversion of the input signal to a digital value."

I'm sorry, but I consider that to be an ill-informed gobbledy-gook statement
....

and

"The letter D used to designate this amplifier class is simply the next
letter after C, and does not stand for digital. Class D and Class E
amplifiers are sometimes mistakenly described as "digital" because the
output waveform superficially resembles a pulse-train of digital symbols,
but a Class D amplifier merely converts an input waveform into a
continuously pulse-width modulated (square wave) analog signal. (A digital
waveform would be pulse-code modulated.)"

Except for the last sentence, this is a correct statement.

Only "mistakenly described" if you ignore the views of the vast majority of
IC and hardware manufacturers, and apply the narrow out of date definition
of "digital", which you do ...

 

[Arfa Daily]

<snip, snip, in fact hack with chainsaw ...>
Well, I've read all you have to say, and I take on board your points, but I
find some of your thinking, as always in these discussions which wake up the
bee that lives in your arse, convoluted at best. You seem to accept that for
better or worse, language is fluid, and word definitions change. For
instance, you go back to a very old definition of the word "gay", but I can
assure you that Enid Blyton meant no such thing in her children's books in
the 40s and 50s, when she described Noddy and Big Ears as having a gay time
in the woods, or the Famous Five playing gaily by the river with their dog.

But then you go on to refuse to accept that the definition or contextual
meaning of any word that you personally consider should be fixed for all
time, might change to reflect changes in the world that makes common use of
that word.

In some ways, it is the way that you pick on tiny facets, and labour them to
the point of being excruciating, to defend a position that is often
contentious, or even potentially untenable, that gives me the most problem
with trying to have a discussion with you. You berate people for not being
able to take on an alternative view of something that you consider them to
be wrong on, but then flatly refuse to even consider modifying your own
position.

For right or wrong, the global meaning of the word "digital" *has* changed,
and if you refuse to acknowledge this, then it doesn't matter how right you
believe you are with the narrow definition that you cling to, in the wider
world of electronics, you will continue to be considered by most, to be
wrong.

I look forward to seeing any comments that the manufacturers may have on
this, but please, don't ask them leading questions that can only have a
reply that you can use to defend your position. Try to keep it simple, as in
"Why do you insist on calling something that is analogue, digital ?"

Just as a matter of interest, do you consider a circuit constructed of
simple logic gates, to be 'digital', even though no numeric values are being
handled by it ?

Arfa

 

[Arfa Daily]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:giiq3p$sqi$1@news.motzarella.org...

So what exactly are you saying here ? That it's right to use the word
"digital" in it's modern context, which all service engineers world-wide
would understand, or not ? Each time I read thru' what you've said, I
arrive
at an opposite conclusion !

I agree. This is a technical issue, not one of getting along with people
from a different society.


Arfa (dah-di-dah)

'K? <grin

Yes, K. End of current transmission. Back to you. "Over" in morse, if you
like.

 

[William Sommerwerck]

"Class D amplifiers can be controlled by either analog or digital
circuits.
The digital control introduces additional distortion called quantization
error caused by its conversion of the input signal to a digital value."

I'm sorry, but I consider that to be an ill-informed gobbledy-gook
statement.

It's overly terse, but quite correct (though I would have said "signals"
rather than "circuits").

 

[bz]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in
news:x943l.24237$Xy3.7335@newsfe01.ams2:

"bz" <bz+ser@ch100-5.chem.lsu.edu> wrote in message
news:Xns9B79EFBEAF73BWQAHBGMXSZHVspammote@130.39.198.139...
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in
news:C3Z2l.7364$T07.4948@newsfe09.ams2:

Again, I say that you are not wrong, in theory, but neither are you
right in practice, when referring to today's much-changed world of
electronics.


If one wants to understand a concept, one makes sure that they
understand how the words are being used.

Understanding what others mean when they use a certain word is
important to
communications.

In many technical fields, 'common words' have 'uncommon definitions'.
This leads to a LOT of misunderstandings and has high costs, but it is
often useful and necessary.

A 'careful communicator' will try to find out what others mean when
they use specific words and tailor their communications to use the
language of the listener. Doing otherwise is as counter productive as
walking into a room full of people that only speak Etruscan and giving
a lecture in Greek.

Arguing about what a word 'really means' is a waste of time and energy.

If one wants to communicate with others, one uses words that others
understand in the way that they understand them.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is
an infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap0



So what exactly are you saying here ? That it's right to use the word
"digital" in it's modern context, which all service engineers world-wide
would understand, or not ? Each time I read thru' what you've said, I
arrive at an opposite conclusion !

When talking to others, it is 'better' to use the meaning of the word, as
THEY define it.

There is nothing to prevent you from saying [often to yourself] '"normally",
I use that word to mean xxxxx [but in this case I will use your definition so
we can communicate].'

I am just trying to point out the fact that it is "pointless" to 'argue' over
the meaning of a word. Either you choose to agree upon a meaning so you can
communicate, or you misunderstand or are "mistook".

I ENJOY playing with words and will often go a mile out of my way to make a
pun.

I *try* to be a careful communicator always, allowing for the fact that
people who are not native English speakers, may well be reading, and
also that many Americans will be reading, who tend to use the language
in a much more 'literal' way than those of us in the UK. That
difference, and the difference in sense of humour, can easily lead to
conflict, so I try to take both of those factors into account when I do
post.

I think that you usually do well.

Maybe I don't get it right all the time, but at least I do try ..

Arfa (dah-di-dah)

As I said, the conversation has been intersting and educational.

di-di-di-dah-di-dah



tu su dit dit




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+spr@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap