Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
..55 , 43, 0

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Class "G" maybe, where the supply on the output devices doubles 'on the fly'
depending on current demand (as in amperes)? Lots of amplifiers are now. The
supplies are often designated "VH" and "VL". First units I ever came across
which used it, were an Aiwa series of hifis, which did the supply switching
with a pair of FETs. I think this covers the principles

http://www.wipo.int/pctdb/en/wo.jsp?...6&DISPLAY=DESC

Arfa

Arfa Daily wrote in message
...

"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of
the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Class "G" maybe, where the supply on the output devices doubles 'on the
fly'
depending on current demand (as in amperes)? Lots of amplifiers are now.
The
supplies are often designated "VH" and "VL". First units I ever came
across
which used it, were an Aiwa series of hifis, which did the supply
switching
with a pair of FETs. I think this covers the principles


http://www.wipo.int/pctdb/en/wo.jsp?...546&DISPLAY=DE
SC

Arfa




I don't have the schematic or even saw the track-side of the Mackie board
but that explains the presence of power FETs

Do you know if the pdf of that OCR'd doc (so no schema) is publicly
available, I could not find it explicitly on that page.



--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"Arfa Daily" wrote in message
...

"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Class "G" maybe, where the supply on the output devices doubles 'on the
fly' depending on current demand (as in amperes)? Lots of amplifiers are
now. The supplies are often designated "VH" and "VL". First units I ever
came across which used it, were an Aiwa series of hifis, which did the
supply switching with a pair of FETs. I think this covers the principles

http://www.wipo.int/pctdb/en/wo.jsp?...6&DISPLAY=DESC

Arfa



Indeed, the SRM450 Bass amp has 2 supplies : +-45v and +-80v. The higher
voltages are switched in with IRFP150 and 160 Fets.

The HF amp is conventional, using just the +-45v supply.



Gareth.

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...

"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of
the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Class "G" maybe, where the supply on the output devices doubles 'on the
fly'
depending on current demand (as in amperes)? Lots of amplifiers are now.
The
supplies are often designated "VH" and "VL". First units I ever came
across
which used it, were an Aiwa series of hifis, which did the supply
switching
with a pair of FETs. I think this covers the principles


http://www.wipo.int/pctdb/en/wo.jsp?...546&DISPLAY=DE
SC

Arfa




I don't have the schematic or even saw the track-side of the Mackie board
but that explains the presence of power FETs

Do you know if the pdf of that OCR'd doc (so no schema) is publicly
available, I could not find it explicitly on that page.




Don't know, to be honest. I just Googled "class G amplifier" to see if I
could find you anything on the principles, and that document seemed to cover
it pretty well. I'm sure that there must be something else out there with
diagrams. If not, let me know, and I'll scan one of the Aiwa schematics for
you. They were reasonably straightforward, as I recall.

Arfa

"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

**There are only Class A, Class A/B, Class B and Class D amplifiers used in
audio. Anything else is just marketing bull****. What you have is a Class
A/B amp, with a switched rail power supply. Class H, Class G, et al are just
marketing terms.


--
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson" wrote in message
...



"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

**There are only Class A, Class A/B, Class B and Class D amplifiers used
in audio. Anything else is just marketing bull****. What you have is a
Class A/B amp, with a switched rail power supply. Class H, Class G, et al
are just marketing terms.


--
Trevor Wilson
www.rageaudio.com.au


Well, you could say that about almost anything. There are many manufacturers
that would disagree with you that it is just marketing bull****. In fact I
can't remember ever seeing anywhere that a piece of regular Joe hifi has
ever been marketed as class G - or even class A/B. I see nothing wrong at
all with giving a derivative of an existing class, a new letter. Whilst
class G is indeed a switched rail class A/B amp, it never-the-less is
different from a fixed rail class A/B amp. Based on what you're saying, you
might as well say that class D is an invalid term, as class A and class B
and class A/B (and for that matter class C at RF as well) refer to the point
that the output devices are biased to in normal operation, whereas class D
refers to an entirely different concept of waveform reconstruction by power
device switching i.e. the fully digital output stage.

Arfa

"Arfa Daily" wrote in message
...

"Trevor Wilson" wrote in message
...



"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of
the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

**There are only Class A, Class A/B, Class B and Class D amplifiers used
in audio. Anything else is just marketing bull****. What you have is a
Class A/B amp, with a switched rail power supply. Class H, Class G, et al
are just marketing terms.


--
Trevor Wilson
www.rageaudio.com.au


Well, you could say that about almost anything.

**Wrong. Classes of amplifiers are clearly and explicityly stated.

There are many manufacturers
that would disagree with you that it is just marketing bull****.

**Of course.

In fact I
can't remember ever seeing anywhere that a piece of regular Joe hifi has
ever been marketed as class G - or even class A/B.

**Here's where I get to say: COMPLETE bull****. Technics, Yamaha and others
have claimed Class A & Class A/B operation for their consumer (as opposed to
audiophile) grade components.

I see nothing wrong at
all with giving a derivative of an existing class, a new letter.

**Me either. Trouble is, it is POWER SUPPLY switching. The fundamental Class
of the amplifier's operation remains Class A, Class A/B or Class B in all
such cases. Rail shifting schemes are not alterations of amplifier Class of
operation.

Whilst
class G is indeed a switched rail class A/B amp, it never-the-less is
different from a fixed rail class A/B amp.

**No, it is not. The amplifier is STILL a Class A/B (or whatever) amplifier,
with a rail switching scheme attached. Of course, that does not suit
marketers, who dreamt up fancy new terms.

Based on what you're saying, you
might as well say that class D is an invalid term,

**Fair comment.

as class A and class B
and class A/B (and for that matter class C at RF as well) refer to the
point that the output devices are biased to in normal operation, whereas
class D refers to an entirely different concept of waveform reconstruction
by power device switching i.e. the fully digital output stage.

**Indeed. The term: Class D has always troubled me. It does not fit with the
accepted Class of operation of an amplifier.


--
Trevor Wilson
www.rageaudio.com.au

"Trevor Wilson" wrote in message
...



"Arfa Daily" wrote in message
...

"Trevor Wilson" wrote in message
...



"N_Cook" wrote in message
...
Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of
the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

in comparison for horn side amp, same devices
0, -43, -.55
.55 , 43, 0

**There are only Class A, Class A/B, Class B and Class D amplifiers used
in audio. Anything else is just marketing bull****. What you have is a
Class A/B amp, with a switched rail power supply. Class H, Class G, et
al are just marketing terms.


--
Trevor Wilson
www.rageaudio.com.au


Well, you could say that about almost anything.

**Wrong. Classes of amplifiers are clearly and explicityly stated.

There are many manufacturers
that would disagree with you that it is just marketing bull****.

**Of course.

In fact I
can't remember ever seeing anywhere that a piece of regular Joe hifi has
ever been marketed as class G - or even class A/B.

**Here's where I get to say: COMPLETE bull****. Technics, Yamaha and
others have claimed Class A & Class A/B operation for their consumer (as
opposed to audiophile) grade components.

I see nothing wrong at
all with giving a derivative of an existing class, a new letter.

**Me either. Trouble is, it is POWER SUPPLY switching. The fundamental
Class of the amplifier's operation remains Class A, Class A/B or Class B
in all such cases. Rail shifting schemes are not alterations of amplifier
Class of operation.

Whilst
class G is indeed a switched rail class A/B amp, it never-the-less is
different from a fixed rail class A/B amp.

**No, it is not. The amplifier is STILL a Class A/B (or whatever)
amplifier, with a rail switching scheme attached. Of course, that does not
suit marketers, who dreamt up fancy new terms.

Based on what you're saying, you
might as well say that class D is an invalid term,

**Fair comment.

as class A and class B
and class A/B (and for that matter class C at RF as well) refer to the
point that the output devices are biased to in normal operation, whereas
class D refers to an entirely different concept of waveform
reconstruction by power device switching i.e. the fully digital output
stage.

**Indeed. The term: Class D has always troubled me. It does not fit with
the accepted Class of operation of an amplifier.


--
Trevor Wilson
www.rageaudio.com.au
I hear what you're saying, Trevor, but it seems to me that we are basically
just dancing around semantics. Granted, it is still a basic class AB or
whatever amplifier, but power supply switching or not, there is still
additional circuitry to detect when the higher rails are required, and it
could be argued that this circuitry is part of the power amp and its overall
design concept.

Given that you accept class D, but are not easy with it, what other
designation would you use to identify the switched rail concept as something
which 'broadly fitted in with the scheme' and allowed engineers to at least
know what it was that they were looking at ? 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 ...

For sure, it's not ideal, and it does fly in the face a little, of what the
original concept of the class lettering system was about, but times move on,
and I think that for clarity, issuing this concept with a new letter, is
acceptable in practice, if not in theory, for the clarity it brings with it.

Arfa

Class D has always troubled me. It does not fit
with the accepted class of operation of an amplifier.

Given that you accept class D, but are not easy with it, what
other designation would you use to identify the switched-rail
concept as something which 'broadly fitted in with the scheme'
and allowed engineers to at least know what it was that they
were looking at?

The original concept of "class" related to the fraction of a cycle the
device was conducting.There's A (all), B (half), AB (more than half but less
than all), and C (less than half). I can't think of any other meaningful
fractions.

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.


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.

How about just _saying_ what it is, in simple language? That would clarify
things for the technician, in a way that tacking on a
marketing-department-selected letter would not.

"William Sommerwerck" wrote in message
...
Class D has always troubled me. It does not fit
with the accepted class of operation of an amplifier.

Given that you accept class D, but are not easy with it, what
other designation would you use to identify the switched-rail
concept as something which 'broadly fitted in with the scheme'
and allowed engineers to at least know what it was that they
were looking at?

The original concept of "class" related to the fraction of a cycle the
device was conducting.There's A (all), B (half), AB (more than half but
less
than all), and C (less than half). I can't think of any other meaningful
fractions.

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.


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.

How about just _saying_ what it is, in simple language? That would clarify
things for the technician, in a way that tacking on a
marketing-department-selected letter would not.



Again William, I hear what you're saying, and I am in broad agreement.
However, when the class lettering system was first used, the world of
amplification was a much simpler place. No one would ever have conceived of
fully digital amplifiers, or ones whose rails switched 'on the fly' as a
result of output stage demand. The class G concept has been around for a
while now, and I don't think that manufacturers have, in general, gone down
the route of all having their own name for it.

As we are all fully aware, language and linguistic interpretation changes
and develops all the time. It is a fact of life that we all accept,
otherwise we would all still be saying "thee" and so on, and "gay" would
still mean carefree and happy. The same is true of electronics. Meanings
change. The world moves on. "Class G" seems to have been accepted pretty
generally by manufacturers as the designation for the type of output stage
topology under discussion, just as "Class D" is now accepted as a fully
digital amplifier, where bias points don't come into it at all, unless you
consider 'hugely on' and 'hugely off' to be valid examples of the term.

I think it is just a case of the system being expanded and adapted to
encompass new ideas, and on that basis, other than for want of being an
historic purist, I really don't have a problem with it, nor do I see why it
should be such a huge problem for others.

At the end of the day, A, AB, C etc are just arbitrary letters to identify
particular amplifier topologies, based on the way they are biased. How the
letter related to the biasing scheme still had to be learnt, and I really
don't see why the system should not have been expanded in the way that it
was, to identify other topologies - even if they are just variants or
derivatives - based on something other than bias points.

Yes, you could say that this is "A class AB amplifier with switched rails",
but how much easier to just say that it's "Class G" ... ??

Arfa

As we are all fully aware, language and linguistic interpretation changes
and develops all the time. It is a fact of life that we all accept,
otherwise we would all still be saying "thee" and so on, and "gay" would
still mean carefree and happy. The same is true of electronics. Meanings
change. The world moves on. "Class G" seems to have been accepted pretty
generally by manufacturers as the designation for the type of output stage
topology under discussion, just as "Class D" is now accepted as a fully
digital amplifier, where bias points don't come into it at all, unless you
consider 'hugely on' and 'hugely off' to be valid examples of the term.

Arfa, please see my other post. Most class D amplifiers are analog, not
digital..


Yes, you could say that this is "A class-AB amplifier with switched
rails",
but how much easier to just say that it's "Class G" ... ??

For that to work, you'd have to have some organization -- such as the IEEE
in the US -- setting standards as to exactly what class-G topology is.

I used to own Krell amplifiers. They were billed as class A, but they were
class A "only" up to about 1/4 or 1/3 full output. Given the crest factor of
acoustically recorded music, this means the amplifier will rarely stray from
class A. But strictly speaking, the amplifier is AB, with (very) high bias.

Most amplifiers are biased only a little beyond class AB. My Parasound A21
amps are unusual, in that they're still in class A up to about one ampere,
which is high for not-horribly expensive amplifier. They are correctly
billed as high-bias class AB.

"William Sommerwerck" wrote in message
...
As we are all fully aware, language and linguistic interpretation changes
and develops all the time. It is a fact of life that we all accept,
otherwise we would all still be saying "thee" and so on, and "gay" would
still mean carefree and happy. The same is true of electronics. Meanings
change. The world moves on. "Class G" seems to have been accepted pretty
generally by manufacturers as the designation for the type of output
stage
topology under discussion, just as "Class D" is now accepted as a fully
digital amplifier, where bias points don't come into it at all, unless
you
consider 'hugely on' and 'hugely off' to be valid examples of the term.

Arfa, please see my other post. Most class D amplifiers are analog, not
digital..

The web in general, would seem to disagree with you on that one, William ...

http://www.pcmag.com/encyclopedia_te...i=55417,00.asp
http://www.pcmag.com/encyclopedia_te...i=55350,00.asp
http://en.wikipedia.org/wiki/Electronic_amplifier
http://www.answers.com/topic/class-d-amplifier
http://www.maxim-ic.com/glossary/ind...063/Tm/class-D

and many many more examples. The signal in a class D amplifier is only
analogue at it's input, and at the speaker terminals after the low pass
filter that removes the HF PWM component. Thus, the whole amplifier is
fundamentally digital in the way that it amplifies the signal applied to it.



Yes, you could say that this is "A class-AB amplifier with switched
rails",
but how much easier to just say that it's "Class G" ... ??

For that to work, you'd have to have some organization -- such as the IEEE
in the US -- setting standards as to exactly what class-G topology is.


Well, to make it totally 'official', I guess that's so, but again, if you
use the web to search for definitions for class G, you will find that pretty
much all manufacturers and describers, use the same definition virtually
word for word, which would suggest that an unwritten 'standard' for what it
is, already exists.



I used to own Krell amplifiers. They were billed as class A, but they were
class A "only" up to about 1/4 or 1/3 full output. Given the crest factor
of
acoustically recorded music, this means the amplifier will rarely stray
from
class A. But strictly speaking, the amplifier is AB, with (very) high
bias.

Most amplifiers are biased only a little beyond class AB. My Parasound A21
amps are unusual, in that they're still in class A up to about one ampere,
which is high for not-horribly expensive amplifier. They are correctly
billed as high-bias class AB.


But surely, that emphasises the point that there are no true 'standards'
applied to the existing letters ?

Arfa

In article ,
"Arfa Daily" wrote:

Much snippage

The class G concept has been around for a
while now, and I don't think that manufacturers have, in general, gone down
the route of all having their own name for it.

The concept has been around, and the "class G" terminology has gone with
it for awhile, too, at least around 30 years. I have a book entitled
"Solid-State Power Electronics," written by one Irving Gottlieb and
copyright 1979, that identifies this circuit topology as a class-G
amplifier (and also discusses classes A, AB, B, C, D, F, and H). While
it may be argued that such a design oughtn't be given a letter
designation, it's hardly worth doing so anymore as a practical matter.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot

Arfa, please see my other post. Most class D amplifiers are analog, not
digital..

The web in general, would seem to disagree with you on that one, William
....


http://www.pcmag.com/encyclopedia_te...i=55417,00.asp

http://www.pcmag.com/encyclopedia_te...i=55350,00.asp
http://en.wikipedia.org/wiki/Electronic_amplifier
http://www.answers.com/topic/class-d-amplifier
http://www.maxim-ic.com/glossary/ind...063/Tm/class-D

and many many more examples. The signal in a class D amplifier is only
analogue at its input, and at the speaker terminals after the low pass
filter that removes the HF PWM component. Thus, the whole amplifier is
fundamentally digital in the way that it amplifies the signal applied to
it.

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

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.

For those who would like to read about the correct explanation of "analog
versus digital", please refer to the following references. (I can't find my
college textbooks, and I don't really think any of these are very good,
because the best explanation is graphical.) Sampling is an analog process,
that involves multiplying the signal by the sampling function, which
produces a convolution in the frequency domain. NO QUANTIZATION OCCURS. If
those convinced that sampling = digitization, let them tell me what the bit
depth is.

http://en.wikipedia.org/wiki/Nyquist...mpling_theorem

http://graphics.cs.ucdavis.edu/~okre...ingTheory.html

http://www2.egr.uh.edu/~glover/apple.../Sampling.html

Here's a quote from the last reference. Note especially the third and
next-to-last sentences.

"The signals we use in the real world, such as our voices, are called
"analog" signals. To process these signals in computers, we need to convert
the signals to "digital" form. While an analog signal is continuous in both
time and amplitude, a digital signal is discrete in both time and amplitude.
To convert a signal from continuous time to discrete time, a process called
sampling is used. The value of the signal is measured at certain intervals
in time. Each measurement is referred to as a sample. (The analog signal is
also quantized in amplitude, but that process is ignored in this
demonstration. See the Analog to Digital Conversion page for more on that.)"

The following is directed at everyone in this group -- and is not a
rhetorical question -- why is it, that when someone _explains_ to you, in a
fairly clear manner, why what you and millions of other people believe to be
true, but _is not_ -- you don't believe them? Aren't you able to think for
yourselves?

The fact that most people do not understand, and refuse to understand, the
difference between analog and digital is, to me, a little frightening,
because it touches on the willingness of human beings to believe what they
want to believe -- or worse, what "experts" tell them -- rather than the
truth.

Disclaimer: When I was a young'un, I thought that if I believed something,
it was so. In retrospect, this is ludicrous, but most people are like that.
It was many years before I recognized this error of thinking.

"William Sommerwerck" wrote in message
...
Arfa, please see my other post. Most class D amplifiers are analog, not
digital..

The web in general, would seem to disagree with you on that one, William
...


http://www.pcmag.com/encyclopedia_te...i=55417,00.asp

http://www.pcmag.com/encyclopedia_te...i=55350,00.asp
http://en.wikipedia.org/wiki/Electronic_amplifier
http://www.answers.com/topic/class-d-amplifier
http://www.maxim-ic.com/glossary/ind...063/Tm/class-D

and many many more examples. The signal in a class D amplifier is only
analogue at its input, and at the speaker terminals after the low pass
filter that removes the HF PWM component. Thus, the whole amplifier is
fundamentally digital in the way that it amplifies the signal applied to
it.

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.


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.


For those who would like to read about the correct explanation of "analog
versus digital", please refer to the following references. (I can't find
my
college textbooks, and I don't really think any of these are very good,
because the best explanation is graphical.) Sampling is an analog process,
that involves multiplying the signal by the sampling function, which
produces a convolution in the frequency domain. NO QUANTIZATION OCCURS. If
those convinced that sampling = digitization, let them tell me what the
bit
depth is.

http://en.wikipedia.org/wiki/Nyquist...mpling_theorem

http://graphics.cs.ucdavis.edu/~okre...ingTheory.html

http://www2.egr.uh.edu/~glover/apple.../Sampling.html

Here's a quote from the last reference. Note especially the third and
next-to-last sentences.

"The signals we use in the real world, such as our voices, are called
"analog" signals. To process these signals in computers, we need to
convert
the signals to "digital" form. While an analog signal is continuous in
both
time and amplitude, a digital signal is discrete in both time and
amplitude.
To convert a signal from continuous time to discrete time, a process
called
sampling is used. The value of the signal is measured at certain intervals
in time. Each measurement is referred to as a sample. (The analog signal
is
also quantized in amplitude, but that process is ignored in this
demonstration. See the Analog to Digital Conversion page for more on
that.)"

The following is directed at everyone in this group -- and is not a
rhetorical question -- why is it, that when someone _explains_ to you, in
a
fairly clear manner, why what you and millions of other people believe to
be
true, but _is not_ -- you don't believe them? Aren't you able to think for
yourselves?


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.



The fact that most people do not understand, and refuse to understand, the
difference between analog and digital is, to me, a little frightening,
because it touches on the willingness of human beings to believe what they
want to believe -- or worse, what "experts" tell them -- rather than the
truth.

You have to draw the line somewhere, and make a judgement as to who or what
an "expert" is. The dictionary defines an expert as someone who has special
skills and knowledge in a subject, and is an authority on that subject.
Would you consider that the man who comes to repair your boiler is an expert
? Or the man who troubleshoots problems at your local garage? I suspect,
like most people you probably would. So if you believed what these people
told you about the dangerous gas leak on your boiler, or that you needed
$300 worth of work doing on your car to make it run right again was the
truth, would that make you frighteningly stupid ?



Disclaimer: When I was a young'un, I thought that if I believed something,
it was so. In retrospect, this is ludicrous, but most people are like
that.
It was many years before I recognized this error of thinking.



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.

The term "digital" may not be a strictly true one for this class of
amplifier, and in truth, there is no such thing as a fully digital amplifier
in the sense that you are advocating, but in the way that most people would
understand the term "analogue", it's not that, either. The reason that it
gets called digital, is because all of the power amplification is done with
devices that have only two states - on and off. And before you say that
those devices are linear ones in that they are transistors of one persuasion
or another, they are not used in that way in this type of output stage.

So, if you are amplifying a signal that has only two levels, using devices
driven to have only the two conditions of on or off, then I think that you
are stretching the imagination more by calling it an analogue process, than
you are by calling it a digital one.

I don't believe that there is a true term for what the process is, but I
also think that "digital" provides for a better understanding of what is
fundamentally going on, than calling it an analogue process as you would.

And for the record, I am perfectly capable of thinking for myself, thank
you, and I am quite happy that I understand the principles of the class D
amplifier, enough to be able to make valid contributions to any discussions
about it. For you to suggest that the entire web, including respected
manufacturers, has got it wrong, seems a little opinionated to me, and based
once again on dancing around terminology and semantics, as popularly
understood by the electronic engineering world at large.

Anyway, I'm not going to get into another of those long-winded ****ing
contests with you over it. If you want to believe that it is an analogue
process, fine, go ahead at that. Right, wrong or indifferent, I will
continue to refer to it as a 'digital' amplifier, as most engineers and
manufacturers would, and indeed do ...

Arfa

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".


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.

On the other hand, if we quantized the level of the sample data, it would
now be in digital form.

"Pulses" have nothing to do with digital. "Numbers" have nothing to do with
digital -- PCM is only one form of digital; there are others. Any time you
represent data samples with a quantized value (which can be represented by
one of a finite group of numbers, but doesn't have to be), it's digital. And
it doesn't matter a whit what the waveform looks like. Ever heard of ECL?
It used sine waves, but it was digital?

You really need to think this though, rather than reacting with a mental
knee-jerk.

I am slightly embarrassed at giving Web references on this topic, which is
what I object to -- appealing to authority. But "you" -- meaning the people
in this group -- should have a sufficient /understanding/ of math and
electronics so that the light bulb goes on when you hear a correct
explanation. "Ah! That's right! I hadn't understood it before! Now I do."

I have to apologize a bit, because I certainly don't understand everything
new the first time I'm exposed to it. But I make an effort to understand
it -- not blindly accept or reject it. I generally don't believe things I
don't understand.


The term "digital" may not be a strictly true one for this class of
amplifier, and in truth, there is no such thing as a fully digital
amplifier
in the sense that you are advocating, but in the way that most people
would
understand the term "analogue", it's not that, either. The reason that it
gets called digital, is because all of the power amplification is done
with
devices that have only two states - on and off. And before you say that
those devices are linear ones in that they are transistors of one
persuasion
or another, they are not used in that way in this type of output stage.

So, if you are amplifying a signal that has only two levels, using devices
driven to have only the two conditions of on or off, then I think that you
are stretching the imagination more by calling it an analogue process,
than
you are by calling it a digital one.

Again, you misunderstand. A PWM signal /does not/ have two levels. If it's
analog, it has an infinite number of levels (widths). If it's digital, it
has a finite number of levels (widths). The data (signal) IS NOT conveyed by
the signal level (which remains constant), but by the pulse width, which can
vary continuously (analog) or in steps (digital).


I don't believe that there is a true term for what the process is, but I
also think that "digital" provides for a better understanding of what is
fundamentally going on, than calling it an analogue process as you would.

And for the record, I am perfectly capable of thinking for myself, thank
you, and I am quite happy that I understand the principles of the class D
amplifier, enough to be able to make valid contributions to any
discussions
about it. For you to suggest that the entire web, including respected
manufacturers, has got it wrong, seems a little opinionated to me, and
based
once again on dancing around terminology and semantics, as popularly
understood by the electronic engineering world at large.

Are you interested in actually understanding things, or in simply parrotting
the majority belief? Does truth = what the majority believe? Really?

About 30 years ago, Pioneer introduced an FM tuner with a pulse-counting
detector. (Pioneer wasn't the first; Fisher had one about 15 years earlier.)
This was billed as digital, when it was wholly analog.

"Truth is truth. You can't have opinions about truth." -- Friendly Professor
Peter Schickele

This is not a ****ing contest. This is my attempt to get other people to
THINK.

I"William Sommerwerck" wrote in
:

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.

On the other hand, if we quantized the level of the sample data, it
would now be in digital form.


In general, your argument is correct and Arfa is mistook.

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].

Although restricting the data to particular levels might be a quantum leap
forward in efficiency, it doesn't really make the processing of the data
'digital' {although one could argue that it HAS been digitized into 'BASE
1024', I think that is really cheating}.

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







--
bz 73 de N5BZ k

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

remove ch100-5 to avoid spam trap

N_Cook wrote:

Before wrapping up a Mackie SRM450 powered speaker I took some
representative DC voltages on the complementary pair power devices of the
bass driver amp, for me and all else, future reference.
-42, -88, -42.8
41.2, 88, 42
What would the circuit type/ class name be, for this sort of biasing?

Class G or H. It's supply switching to reduce dissipation. Done it myself.
Big amps may have 3 rails.

Graham

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 ?


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.

Graham

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 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.

"William Sommerwerck" wrote in message
...
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 ********
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

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
********
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.

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

"William Sommerwerck" wrote in message
...
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
********
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.



OK. I'm going to take one last stab at this. You are right. But at the same
time, you are wrong also. You are applying an out of date definition to a
grey subject, and trying to make it black and white by using that
definition.

To use the linguistic analogy again. Thirty years ago, the word "gay" meant
happy and carefree. Then it was hijacked by homosexuals to describe
themselves in what they felt was a less contentious way. Now if I want to be
linguistically accurate, the word, thirty years later, still means nothing
other than happy and carefree. But a gazillion homosexuals around the world
would disagree with me very strongly. Are they wrong, and me with my lone
voice, right ? No, neither of us is right or wrong. I am theoretically
right, and they are practically right, because the word has now been
accepted into modern language to mean something other than its 'real'
original definition.

The same is true of the word "digital". Thirty years ago, your narrow
definition of a digital signal being one that has been quantized into
representative numbers, was correct. You could not have applied an analogue
audio signal to a Z80 data line, and have expected it to have been able to
do anything with it. However, now, you could apply a two level PWM audio
signal, which you contend is really still analogue, to a port pin on a
completely digital uP IC, and it would have no problem being able to
manipulate that signal, given the appropriate code to do so. The world of
electronics has moved on since the original definition of digital, and the
lines between analogue and digital signal processing, have become much more
fuzzy in the process, to the point where the original 'narrow' theoretical
definition of digital, no longer hacks it in the real world.

Whether or not you like it, or think it right, the word "digital" now tends
to encompass any means of data transfer between devices or equipments, or
any signal processing technology, which employs just two levels. Any
engineer working in the real world of electronics will tell you this. The
many millions of people who believe this, and publish on the web, are *not*
wrong, just because you believe that they are.

Yamaha for instance, define a PWM audio signal as being digital, and with no
apology, see

http://www.global.yamaha.com/news/2003/20031002.html

Do you honestly consider that the designers at a well respected company such
as they, are wrong ?

Likewise, Sanken and Sanyo describe their PWM class D amplifier ICs as being
"digital". Wrong also ?

And Tripath with their famous TA2020 IC used in many home cinema systems ?

Kenwood ? Sony ? JVC maybe ? All wrong to call their PWM based class D
amplifiers, "digital" ?

If you really believe this, then might I suggest that you try e-mailing a
few of their technical or design departments, and put it to them that they
are wrong, and outline your reasoning, based on your definition of the word,
and then report back what they have to say to you ?

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.

Arfa

"Arfa Daily" wrote in
:

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.

remove ch100-5 to avoid spam trap

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

"bz" wrote in message
98.139...
"Arfa Daily" wrote in
:

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.

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

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.

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

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

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.

OK. I'm going to take one last stab at this. You are right. But at the
same time, you are wrong also. You are applying an out-of-date
definition to a grey subject, and trying to make it black and white
by using that definition.

The definition of what is analog data and what is digital data is fixed, and
will not change. The reason you're reluctant to accept it is that, like all
human beings -- myself included -- you're reluctant to alter the way you
think.


To use the linguistic analogy again. Thirty years ago, the word "gay"
meant happy and carefree. Then it was hijacked by homosexuals
to describe themselves in what they felt was a less contentious way.

This is not correct. The term, as a synonym for "homosexual", appears to
have been in use since at least the middle 17th century. It actually means
"loose", "depraved", "low-life", etc, and was originally derogatory (or at
least disapproving). The Oxford English Dictionary gives the following
definitions (among others) and source examples:

2. a. Addicted to social pleasures and dissipations. Often euphemistically:
Of loose or immoral life. Esp. in gay dog, a man given to revelling or
self-indulgence; gay Lothario: see Lothario.

1637 Shirley Lady of Pleasure v. K1b, Lord. You'le not be angry, Madam. Cel.
Nor rude, though gay men have a priviledge. 1700 T. Brown tr. Fresny's
Amusem. Ser. & Com. 130 Every Dunce of a Quack, is call'd a Physician+Every
Gay thing, a Chevalier. 1703 Rowe Fair Penit. v. i, Is this that Haughty,
Gallant, Gay Lothario? 1754 Adventurer No. 124 37 The old gentleman, whose
character I cannot better express than in the fashionable phrase which has
been contrived to palliate false principles and dissolute manners, had been
a gay man, and was well acquainted with the town. 1791 Burke Let. to Member
Nat. Assembly Wks. VI. 36 The brilliant part of men of wit and pleasure, or
gay, young, military sparks. 1798 Ferriar Illustr. Sterne ii. 40 The
dissolute conduct of the gay circles in France is not of modern date. 1847
H. Rogers Ess. I. v. 214 For some years he lived a cheerful, and even gay,
though never a dissipated life, in Paris. 1849 Macaulay Hist. Eng. vi. II.
103 The place was merely a gay suburb of the capital. 1851 Mayhew Lond.
Labour I. 382 The principal of the firm was what is termed ‘gay’. He was
particularly fond of attending public entertainments. He sported a little as
well, and delighted in horse-racing. 1891 E. Peacock N. Brendon I. 302 This
elder Narcissa had led a gay and wild life while beauty lasted. 1897 J.
Hutchinson Archives Surg. VIII. 224 My patient was a married man, who
admitted having been very gay in early life. 1900 G. Swift Somerley 54 Oh!
that first kiss! how proud of it we are, what gay dogs we feel! 1910 S.
Kaye-Smith Spell Land xix. 221 He felt rather a gay dog. 1849 Macaulay
Hist. Eng. ii. I. 196 On the vices of the young and gay he looked
with+aversion.

2. b. Hence, in slang use, of a woman: Leading an immoral life, living by
prostitution.

1825 C. M. Westmacott Eng. Spy II. 22 Two sisters—both gay. 1857 J. E.
Ritchie Night Side Lond. 40 The gay women, as they are termed, are worse off
than American slaves. 1868 Sund. Times 19 July 5/1 As soon as ever a woman
has ostensibly lost her reputation, we, with a grim inappositeness, call her
‘gay’. 1885 Hull & Linc. Times 26 Dec. 8/4 She was leading a gay life.


The fact that any particular word has different meanings in different
contexts is meaningless in this discussion -- in any discussion, for that
matter. The /only/ example in science or engineering I'm aware of is
"torque", which is supposed to mean "rate of change of angular momentum",
but also has the meaning of "force x distance" (where distance is the
distance from the point of application of the force to the center of
rotation).

English is a wonderfully rich and complex language. Unfortunately, there is
no official body (as the French have) attempting to keep the language fixed.
This can be a bad thing when words are redefined by common usage, * which
weakens the language's vigor. Perhaps the worst example (to a logophile like
myself) is the recent use of "impact" as verb (which it didn't used to be),
to replace many stronger, more-appropriate, more-vigorous, and more-subtle
words: alter, modify, influence, affect, confront, vary, harm, ruin, change,
etc, etc, etc...

I also dislike changing the pronunciation of words, which has the same
effect: "Clique" is pronounced "cleek", not "click". Pronouncing it the
latter way creates an unnecessary homonym.

* The OED is based on common usage, not the opinions of "experts".


Now if I want to be linguistically accurate, the word, thirty years later,
still means nothing other than happy and carefree.

What do you mean by linguistic? For better or worse, the English language
has changed, and will continue to change.


But a gazillion homosexuals around the world would disagree with me
very strongly.

I, for one, don't like the word. I describe myself as "homosexual" or
"queer".


Are they wrong, and me with my lone voice, right? No, neither of us is
right or wrong. I am theoretically right, and they are practically right,
because the word has now been accepted into modern language to mean
something other than its 'real' original definition.

I, too, would prefer that words kept their "original" meanings. Other than
censoring printed documents, there doesn't seem to be any way to do it,
except complaining vigorously and hoping English teachers will set an
example.

Perhaps it's not pertinent, but what about Shakespeare? He /added/ many
words to English (though whether all of them were his coinage, or merely
their first appearance in print is debatable). And we still add words, or
broaden their meanings, which can be a good thing.

By the way, note the misuse of common expressions, the most-common of recent
examples is the conversion of "the proof of the pudding is in the eating" to
"the proof is in the pudding". (ARRRGGGHHH!) Shakespeare's "one fell swoop"
is almost always misued -- in most cases it should be "one swoop". (Note the
meaning of "fell", and the phrase's usage in "The Scottish Play".)


The same is true of the word "digital". Thirty years ago, your narrow
definition of a digital signal being one that has been quantized into
representative numbers, was correct. You could not have applied an
analogue
audio signal to a Z80 data line, and have expected it to have been able to
do anything with it. However, now, you could apply a two level PWM audio
signal, which you contend is really still analogue, to a port pin on a
completely digital uP IC, and it would have no problem being able to
manipulate that signal, given the appropriate code to do so. The world of
electronics has moved on since the original definition of digital, and the
lines between analogue and digital signal processing, have become much
more fuzzy in the process, to the point where the original 'narrow'
theoretical
definition of digital, no longer hacks it in the real world.

I believe in calling a knife a knife. (Here's an example of (a sort-of)
re-definition: In Italian, "spada" means "sword", not "spade".) Where is the
logic in allowing a clearly defined scientific or technical term to be
incorrectly redefined by common usage?


However, now, you could apply a two-level PWM audio
signal, which you contend is really still analogue.

A "two-level" signal (or a signal with any finite number of defined levels)
is, by definition, digital. But a PWM signal, regardless of its amplitude,
can be analog or digital. It is how the width of the pulse varies
(discretely or continuously) that determines digital or analog, not the fact
that it's a pulse. The width (not the amplitude) of the PWM signal is its
(signal) "level".


Whether or not you like it, or think it right, the word "digital" now
tends
to encompass any means of data transfer between devices or equipments,
or any signal processing technology, which employs just two levels.

But (as I pointed out above), the levels DO NOT convey the data! The change
in amplitude (from 0 to B+, and back again) has nothing to do with the
information being transmitted. To refer to all data-transmission systems
that use pulses "digital" is to ignore the clear meanings of these terms.

There are lots of people who think Einsteinian relativity is a pile of crap.
Does that make it so? If the majority of people did, would it be so?

I don't mean this sarcastically, but does it bother you when I get upset
when people say things that show they don't fully understand what they're
talking about? I think this should bother everyone.


Any engineer working in the real world of electronics will tell you this.
The many millions of people who believe this, and publish on the web,
are *not* wrong, just because you believe that they are.

This is Humpty-Dumptyism -- a word has a particular meaning because I say it
does.


Yamaha for instance, define a PWM audio signal as being digital,
and with no apology, see
http://www.global.yamaha.com/news/2003/20031002.html
Do you honestly consider that the designers at a well-respected
company such as they, are wrong ?

I have no idea what the designers think, as this product sheet was (likely)
written by Americans in Yamaha's marketing department. But engineers have
been known to be wrong.

Analog signal input circuits, pulse width-modulation circuits (Note 2),
bridge-tied load (BTL) output circuits (Note 3), self-oscillating circuits
(Note 4), overcurrent protection circuits, pop-noise suppression circuits
(Note 5), headphone amps, and other components necessary for digital
amplifiers are combined in an extremely small 28-pin TSSOP.

There's nothing about an S/PDIF input, so I have to assume the PWM is
analog, not digital. Note 2 reads "Pulse width-modulation circuits: The
circuits lengthen and shorten the widths of digital pulses, amplifying the
voltage of sound signals."

A pulse is neither analog nor digital. It's how it's used to convey data
that determines "digital" or "analog".


Likewise, Sanken and Sanyo describe their PWM class D
amplifier ICs as being "digital". Wrong also?

Yup.


And Tripath with their famous TA2020 IC used in many
home-cinema systems?

The block diagram suggests that the pulse width is modulated directly (ie,
there is no quantization -- what would be the point, as it would needlessly
complicate the circuit?), so, yes, this is an analog amp.


Kenwood? Sony? JVC maybe? All wrong to call their PWM-based
class D amplifiers, "digital"?

Wrong, wrong, and wrong. They are switching amplfiers, and probably analog.


If you really believe this, then might I suggest that you try e-mailing a
few of their technical or design departments, and put it to them that they
are wrong, and outline your reasoning, based on your definition of the
word,
and then report back what they have to say to you?

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.

There is an issue of personality here. Being queer, I'm not willing to agree
with the majority. Other people are more-affable, and willing to bend to the
general view. In social matters, they're usually right. In
scientific/technical matters, I don't understand why misunderstanding the
facts doesn't greatly bother people.

"Experts" can be wrong. It's almost certain that Einstein was wrong in
rejecting the implication of quantum physics that, on the sub-microscopic
level, there is no cause and effect -- events occur statistically,
determined by the "maths", not because there is a causative force. He didn't
like it -- "God does not play dice!" -- and rejected it, despite the math
and laboratory observations being against him.


I'm going to do something I hate doing. I have to call Naitonal
Semiconductor next week about a job. I will ask Martin Giles (one of your
countrymen, and an extremely intelligent fellow *) how he feels about this
issue, from both a technical and practical matter. I will also send e-mail
to Bob Pease, National's chief designer, guru, mascot, and resident
curmudgeon, though I doubt he'll reply.

I'll report back what they have to say (if anything).

* How do I know he's intelligent? Because a few years ago, I asked him what
the one basic principle you needed to explain to someone who was learning to
design op-amp circuits was -- and he instantly came back with the correct
answer.

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.

"William Sommerwerck" wrote in message
...
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 ...

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

"William Sommerwerck" wrote in message
...
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.

"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").

"Arfa Daily" wrote in
:


"bz" wrote in message
98.139...
"Arfa Daily" wrote in
:

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.

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.

remove ch100-5 to avoid spam trap