[Eeyore]

Ian Iveson wrote:

The dB is a ratio of powers.

Bwahahahahahaahahahaaa !

Every one's a cracker !

I take it you are the group's clown?

You already hold that title and in all the other audio groups too. You are
uniquely wrong about almost everything you post.

The absence of the word 'logathmic' in your statement above is somewhat critical
btw.

Graham

[Eeyore]

Randy Yates wrote:

"Paul Stamler" writes:
"Randy Yates" wrote

There is no corruption that I know of. dBU, dBV, dBm, etc., etc.,
all essentially are related to power ratios.

Not dBu or dBV.

Yes, dBu and dBV.

Oh for God's sake - GROW UP.

The obsession some peopole have about equating dB with POWER is utterly
ridiculous.

Graham

[[email protected]]

On Oct 23, 10:56 am, Eeyore
wrote:
The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

dB: Abbreviation for decibel (s). One tenth of the common
logarithm of the ratio of relative powers, equal to 0.1 B
(bel). Note 1: The decibel is the conventional relative
power ratio, rather than the bel, for expressing relative
powers because the decibel is smaller and therefore
more convenient than the bel. The ratio in dB is given by

dB = 10 log (P1/P2)

where P 1 and P 2 are the actual powers. Power ratios
may be expressed in terms of voltage and impedance,
E and Z, or current and impedance, I and Z, since

P = I^2*Z = E^2/Z

Thus dB is also given by

dB = 10 log ( (E1^2/Z1) / (E2^2/Z2) )
= 10 log ( (I1^2*Z1) / (I2^2*Z2) )

If Z1= Z2, these become

dB = 20 log (E1/E2)
= 20 log(I1/I2)

Note 2: The dB is used rather than arithmetic ratios
or percentages because when circuits are connected
in tandem, expressions of power level, in dB, may be
arithmetically added and subtracted. For example, in
an optical link, if a known amount of optical power, in
dBm, is launched into a fiber, and the losses, in dB,
of each component (e.g., connectors, splices, and
lengths of fiber) are known, the overall link loss may
be quickly calculated with simple addition and
subtraction.

Yesiree, ATIS, ITU, IEC, AES, NIST all show the same
obsession with the utterly ridiculous concept of equating
dB and power.

Looks like you got your work cut out for you.

[g]

In article , Eeyore wrote:


Randy Yates wrote:

"Paul Stamler" writes:
"Randy Yates" wrote

There is no corruption that I know of. dBU, dBV, dBm, etc., etc.,
all essentially are related to power ratios.

Not dBu or dBV.

Yes, dBu and dBV.

Oh for God's sake - GROW UP.

The obsession some peopole have about equating dB with POWER is utterly
ridiculous.

Graham

I don't know, when I need to convert things, I open up my little pocket
reference book, and there is a row for voltage, and a row for power.
When I want to get a clearer idea of ratios, I usually convert to voltage.

greg

[John Phillips]

On 2007-10-23, wrote:
On Oct 23, 10:56 am, Eeyore
wrote:
The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

The trouble lies when common practice and official definition differ.
This happens when the writers of definitions fail to meet the needs of
the practitioner, or when practice changes so this becomes so.

If I have an audio power amplifier with a voltage gain of 10 then talking
of a voltage gain of 20*log(10) = 20 dB is more useful in practice than
taking an input impedance of (say) 10 kOhms and a load of (nominally)
8 Ohms and calling the power gain 51 dB because of the impedance change.

--
John Phillips

[Paul Stamler]

"Randy Yates" wrote in message
...

In this case, f(x) is also invertible if we constrain the domain of
x to be non-negative values, and the inverse is g(y) = k * y^(1/2).

So it is that, in the case of dBu and dBV, WE USE POWER TO DETERMINE
VOLTAGE, and WE ESTABLISH POWER BY ASSUMING AN IMPEDANCE AND MEASURING
VOLTAGE.

No. We measure a voltage using a meter which, ideally, draws no power
whatsoever because it has an infinitely high input impedance. Modern VTVMs
are close enough to that ideal as makes no nevermind. The meter mechanism is
measuring voltage, pure and simple. Not power. Could you compute power?
Sure. That doesn't mean the direct quantity you're measuring is power. It
isn't. Not the way voltmeters work. Their needle deflection is a function of
voltage and only voltage (well, and the countervailing spring tension).

If I want to measure power, I can do that separately -- my voltmeter lets me
turn a switch and do that too, using a defined load (600 ohms, or 16, 8 or 4
ohms) and a different scale. In that case, yes, the voltmeter is deriving
power from a voltage measurement. But in practice I find myself needing to
do that very rarely, so I stay on the dBu scale.

Yes, I agree that in the case of dBu and dBV the primary quantity
of interest is VOLTS. However, that does NOT make a dBu or dBV a
voltage!

Never said a dBu or dBV was a voltage. I said dBu and dBV are units unto
themselves, *derived from a voltage* which is measured by a voltmeter
without regard to impedance.

Why bother? BECAUSE IT'S USEFUL. It turns out measuring dBu (and
occasionally dBV) is easily applicable to the design and use of modern audio
systems. Once in a while working with dBm is also useful, but not often. I
go with what is useful.

Operant Definition: dBu = what you measure with a meter calibrated in dBu.
The quantity can be computed using the formula dBu = 20 * log (V/.775V),
with due consideration of how the voltage was measured (rms or whatever).
Practical analog voltmeters include a dBu scale which is essentially a
nomogram for performing the voltage-to-dBu computation.

Peace,
Paul

[Paul Stamler]

wrote in message
ps.com...
On Oct 23, 10:56 am, Eeyore
wrote:
The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

dB: Abbreviation for decibel (s). One tenth of the common
logarithm of the ratio of relative powers, equal to 0.1 B
(bel).

dB /= dBu /= dBV /= dBSPL.

Peace,
Paul

[bg]

Mike Rivers wrote in message
om...
On Oct 22, 1:35 pm, "Ian Iveson"

This is a regular argument here. Sometimes you just have to accept
corruption of the pure definition because other variations have come
into common useage.

Shall we talk about phase now?

Exactly!!!!!!!
Wasn't this a conspiracy made up by the phone company to distract people
from owning thier own equipment?
bg

[bg]

Chris Hornbeck wrote in message ...
On Mon, 22 Oct 2007 15:59:36 -0700, Mike Rivers
wrote:

The dB is a ratio of powers. An increase of 3dB will always
result in a doubling of power, regardless of whether you are
talking about a voltage, a pressure, or a power.

So how do you explain the common usage of doubling voltage being a 6
dB increase? If you double the voltage into a given load, you do
increase the power by 3 dB, but we're not interested in power when we
want to talk about voltage.

Proving conclusively that *everybody* can make errors
in discussing this topic. Makes it a real perennial
chestnut, fersure.

Here's my take: dB is dB is dB into a given load. The
"given load" part what most often trips up the flow of
conversation.

Thanks, as always,

Chris Hornbeck
"Dreams, Amelia, dreams and false alarms." -RJA

But how about when you say a certain op amp has an open loop gain of 80db.
There is nothing implied about Z or W. All that is known is that the gain is
10,000 and it is assumed that it is a voltage gain.
bg

[Mike Rivers]

On Oct 23, 3:32 pm, "bg" wrote:

But how about when you say a certain op amp has an open loop gain of 80db.
There is nothing implied about Z or W. All that is known is that the gain is
10,000 and it is assumed that it is a voltage gain.

Well, you know it's an op amp, and with an op amp, the output
impedance is very low and the input impedance is kind of middlin-high.
Pretty much like any modern piece of audio gear (even a power
amplifier).

[Chris Hornbeck]

On Tue, 23 Oct 2007 16:58:45 GMT, "Paul Stamler"
wrote:

Yes, I agree that in the case of dBu and dBV the primary quantity
of interest is VOLTS. However, that does NOT make a dBu or dBV a
voltage!

Never said a dBu or dBV was a voltage. I said dBu and dBV are units unto
themselves, *derived from a voltage* which is measured by a voltmeter
without regard to impedance.

I would go further and say that a dBu or a dBV *is* a voltage.
Either maps one-to-one to a linearly (or any other way) expressed
voltage. To my simple mind that makes 'em ducks, er, voltages.
As much as anything else, at least. No need to hold their
disreputable past against 'em.

I promise this is my last bleating on the topic.

Thanks, as always,

Chris Hornbeck
"Dreams, Amelia, dreams and false alarms." -RJA

[Randy Yates]

"Paul Stamler" writes:

wrote in message
ps.com...
On Oct 23, 10:56 am, Eeyore
wrote:
The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

dB: Abbreviation for decibel (s). One tenth of the common
logarithm of the ratio of relative powers, equal to 0.1 B
(bel).

dB /= dBu /= dBV /= dBSPL.

How does establishing a reference level make any of these something
other than power?
--
% Randy Yates % "Rollin' and riding and slippin' and
%% Fuquay-Varina, NC % sliding, it's magic."
%%% 919-577-9882 %
%%%% % 'Living' Thing', *A New World Record*, ELO
http://www.digitalsignallabs.com

[Randy Yates]

"Paul Stamler" writes:
[...]

You know Paul, there's not a single thing you said in this post that I
didn't already know. There's not a single surprise. For me, the
information content of this post was zero, and nothing in it gave me
even the weakest notion to consider that maybe I've got it wrong and you
have a point.

It is so obviously clear to me and apparently so obscure to you that I
am at a loss as to how further to proceed. I have made an honest
attempt to present you and others with the truth. That truth can be
stated simply as this: The bel is defined as a ratio of powers.

You and others are most certainly free to ignore this truth and doggedly
follow your own erroneous conclusions.
--
% Randy Yates % "My Shangri-la has gone away, fading like
%% Fuquay-Varina, NC % the Beatles on 'Hey Jude'"
%%% 919-577-9882 %
%%%% % 'Shangri-La', *A New World Record*, ELO
http://www.digitalsignallabs.com

[Chronic Philharmonic]

"Mike Rivers" wrote in message
oups.com...
On Oct 22, 11:42 pm, "Chronic Philharmonic"
wrote:

The thing is, dB is a unitless quantity. The same number can refer to
voltage, current, pressure and power all at the same time. That's the
beauty
of it.

This is why we talk about dB of change, at least those of us who use
the term correctly. There are many who don't use the term correctly,
but they still seem to recognize the concept of change or difference.

There are, however, certain conventions that have been established and
should be understood. A common nominal operating level for analog line
level audio signals is 1.22765.... volts. Why such an odd number?
Well, it was initially derived from a power level. The voltage
required to pump 1 milliwatt into a 600 ohm load is 0.775V. You can do
the arithmetic. But when they hooked a voltmeter across a 600 ohm
load being fed 1 mW, the meter didn't go very far up scale. So they
cranked up the voltage until they got a reading of about 2/3 full
scale, and that became the standard operating level. It just happened
to be 4 dB worth of more volts than what they got out of the voltage
that gave them 1 mW.

So that's where we get the reference voltage for dBu. I'd like to say
that "everybody knows that" but they don't. Still, "everybody knows"
about +4 dBu even if they say "+4 dB." We who want to understand
understand.

Most people don't really have a good idea of what a change in SPL by 3
dB really means in practice unless they have an SPL meter. So we tend
to make some assumptions of how it relates to the power driving the
source (whether it's a power amplifier driving a loudspeaker or a
chemical reaction making noise from a jet engine). We can adjust the
voltage going into the power amplifier, read that change in dB on a
meter on the console, and hear the result.

So I just connected a pink noise generator to a speaker, held my
trusty Radio Shack SPL meter about a foot away from the speaker, and
observed that there was a 1:1 correspondence between changes in dB on
the generator and dB on the SPL meter. Drop the level of the noise
coming out of the generator by half (6 dB on the generator's output
level scale) and the SPL as read on the meter drops by 6dB. Is there
any wonder that people are confused?

But that's just it... They shouldn't be confused. On a transcontinental
telephone line, a 3dB change is 3dB whether they're measuring voltage,
current, power, or the speed of squirrels on a wheel.

[Paul Stamler]

"Randy Yates" wrote in message
...
"Paul Stamler" writes:
[...]

You know Paul, there's not a single thing you said in this post that I
didn't already know. There's not a single surprise. For me, the
information content of this post was zero, and nothing in it gave me
even the weakest notion to consider that maybe I've got it wrong and you
have a point.

It is so obviously clear to me and apparently so obscure to you that I
am at a loss as to how further to proceed. I have made an honest
attempt to present you and others with the truth. That truth can be
stated simply as this: The bel is defined as a ratio of powers.

You and others are most certainly free to ignore this truth and doggedly
follow your own erroneous conclusions.

Mr. Yates, you are apparently immune to surprise. So be it. You are a
prescriptivist. Many on this list, including myself, are descriptivists.
What that means, since you already know but I'll tell you anyway, is that
prescriptivists believe language is defined by authorities (dictionaries,
reference manuals, etc.). whereas descriptivists believe languaged is
defined by common and mutually understood usage.

You are entirely right, within your frame of reference: the relevant
authorities do indeed define a bel (and, by extension, a decibel) as a unit
related to powers. And I am entirely right, within my frame of reference:
the people actually practicing audio use the units dBu and dBV to describe
voltages rather than powers. Are the authorities wrong? Are the
practitioners wrong? First, I think, one needs to define "wrong", and to do
that, you have to get into a discussion, in Bill Clinton's terms, of what
the meaning of "is" is. Which is pointless.

Peace,
Paul

[Eeyore]

John Phillips wrote:

wrote:
Eeyore wrote:

The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

The trouble lies when common practice and official definition differ.
This happens when the writers of definitions fail to meet the needs of
the practitioner, or when practice changes so this becomes so.

If I have an audio power amplifier with a voltage gain of 10 then talking
of a voltage gain of 20*log(10) = 20 dB is more useful in practice than
taking an input impedance of (say) 10 kOhms and a load of (nominally)
8 Ohms and calling the power gain 51 dB because of the impedance change.

Except it won't be 51dB because the speaker impedance (and both its real and
imaginary parts) vary hugely with frequency.

It may be 51dB of power gain at some spot frequency only.

Power gain is for the most part an utterly pointless idea these days.

Graham

[Eeyore]

Randy Yates wrote:

"Paul Stamler" writes:
wrote in message
Eeyore wrote:

The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

dB: Abbreviation for decibel (s). One tenth of the common
logarithm of the ratio of relative powers, equal to 0.1 B
(bel).

dB /= dBu /= dBV /= dBSPL.

How does establishing a reference level make any of these something
other than power?

None of the above are measures of power.

Graham

[Eeyore]

Chris Hornbeck wrote:

"Paul Stamler" wrote:

Yes, I agree that in the case of dBu and dBV the primary quantity
of interest is VOLTS. However, that does NOT make a dBu or dBV a
voltage!

Never said a dBu or dBV was a voltage. I said dBu and dBV are units unto
themselves, *derived from a voltage* which is measured by a voltmeter
without regard to impedance.

I would go further and say that a dBu or a dBV *is* a voltage.

That is indeed how they are DEFINED !

Graham

[William Sommerwerck]

"Eeyore"
wrote in message ...

Power gain is for the most part an utterly pointless idea these days.

Right. Its significance dates to the early days of electronics, when
amplifier stages were transformer-coupled. The invention of RC coupling
rendered it less significant.

[Eeyore]

William Sommerwerck wrote:

"Eeyore" wrote

Power gain is for the most part an utterly pointless idea these days.

Right. Its significance dates to the early days of electronics, when
amplifier stages were transformer-coupled. The invention of RC coupling
rendered it less significant.

That's certainly a large part of it.

I'd say modern IC op-amp circuitry which enables very high impedance input, low
output impedance gain blocks (without the need for matched impedance working)
finished the job.

Note that where the above doesn't apply such as in RF circuitry, power gain is
still the norm.

Graham

[Randy Yates]

"Paul Stamler" writes:

"Randy Yates" wrote in message
...
"Paul Stamler" writes:
[...]

You know Paul, there's not a single thing you said in this post that I
didn't already know. There's not a single surprise. For me, the
information content of this post was zero, and nothing in it gave me
even the weakest notion to consider that maybe I've got it wrong and you
have a point.

It is so obviously clear to me and apparently so obscure to you that I
am at a loss as to how further to proceed. I have made an honest
attempt to present you and others with the truth. That truth can be
stated simply as this: The bel is defined as a ratio of powers.

You and others are most certainly free to ignore this truth and doggedly
follow your own erroneous conclusions.

Mr. Yates, you are apparently immune to surprise. So be it. You are a
prescriptivist. Many on this list, including myself, are descriptivists.
What that means, since you already know but I'll tell you anyway, is that
prescriptivists believe language is defined by authorities (dictionaries,
reference manuals, etc.). whereas descriptivists believe languaged is
defined by common and mutually understood usage.

In my opinion, descriptionism has no place in technical and scientific
fields, which are by nature required to be precise. There are questions
such as who decides these definitions and how long their definitions
should hold, and I admit I don't know how to address such questions. If
we sidestep these questions, it appears to me that certain terms are
absolutely clear, having been defined clearly in multiple authoritative
texts for some time, and the bel is one of them.

I agree, however, that your point goes to the heart of our conflict (and
probably everyone else's).

I will point out one not-so-small counter-indication, even for the
descriptionist, in your position, and that is simply that

20 log(Vmeasured / Vreference) = 10 log[(Vmeasured / Vreference)^2],

and that highly suggests that a) we are using the original "bel" (since
the expression involves "10 log()"), and b) we are describing a ratio of
powers (since it involves the ratio of square voltages).
--
% Randy Yates % "Ticket to the moon, flight leaves here today
%% Fuquay-Varina, NC % from Satellite 2"
%%% 919-577-9882 % 'Ticket To The Moon'
%%%% % *Time*, Electric Light Orchestra
http://www.digitalsignallabs.com

[Mike Rivers]

On Oct 23, 8:16 pm, Randy Yates wrote:

It is so obviously clear to me and apparently so obscure to you that I
am at a loss as to how further to proceed.

In that case, please don't. You're arguing science, some of us are
arguing practice.

I have made an honest
attempt to present you and others with the truth. That truth can be
stated simply as this: The bel is defined as a ratio of powers.

Sure. And the sky isn't blue, it just filters out most light that
isn't blue. Take your pedantic arguments back to the lab where things
don't have to work as long as they can be described mathematically.

You and others are most certainly free to ignore this truth and doggedly
follow your own erroneous conclusions.

We aren't ignoring the truth, we're just not applying it where it
doesn't apply.

[Arny Krueger]

"Eeyore" wrote in message
...


William Sommerwerck wrote:

"Eeyore" wrote

Power gain is for the most part an utterly pointless idea these days.

Right. Its significance dates to the early days of electronics, when
amplifier stages were transformer-coupled. The invention of RC coupling
rendered it less significant.

That's certainly a large part of it.

Agreed. Also, when you don't have a lot of gain or power to waste, and your
biggest source of losses is the transmission line, then impedance matching
can be very significant.

Electronic amplification technology was initially largely driven by movie
sound, and movie sound was initiated largely by Western Electric and Bell
Labs. They just redirected a lot of the technology that they developed for
long distance phone lines to movie sound.

RCA was another big player in early movie sound, but they were stronger in
radio communications. Radio technology overlapped telephone technology quite
a bit.

I'd say modern IC op-amp circuitry which enables very high impedance
input, low
output impedance gain blocks (without the need for matched impedance
working)
finished the job.

My recollection is that solid state pro gear created the turning point.
Transistors made it much more practical to use electronically balanced
inputs to get a big cost savings over transformers. ICs frosted that cake.

Note that where the above doesn't apply such as in RF circuitry, power
gain is
still the norm.

Impedance matching in RF circuits, as I'm sure you know Graham, is justified
by the fact that impedance mismatch causes standing waves in transmission
lines that are a good fraction of a wavelength long.

The fun begins when audiophiles start applying the same kind of thinking to
interconnects and speaker cables for their living rooms! They don't know
that wavelength matters and the wavelength of 20 KHz in wire usually over a
dozen miles.

[Mark]

The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

But Randy, you must admit it has now become VERY COMMON PRACTICE to
use dB for Voltage ratios as well.

A very common example someone mentioned is in the specification of the
open loop VOLTAGE gain of an op amp. When they say the voltage gain =
80 dB that is clearly a VOLTAGE ratio and not a POWR ratio. The power
gain is actually much high due to the low output and high input
impedance.

It may be time to change the official definition to better agree with
common practice.

Mark

[Paul Stamler]

"Arny Krueger" wrote in message
. ..

Electronic amplification technology was initially largely driven by movie
sound, and movie sound was initiated largely by Western Electric and Bell
Labs. They just redirected a lot of the technology that they developed for
long distance phone lines to movie sound.

And, to amplify that point (sorry), the technology of electrical sound
recording was, according to one source I've read, developed to record the
results of their experiments in long-distance telephony.

Peace,
Paul

[Paul Stamler]

"Randy Yates" wrote in message
...

I will point out one not-so-small counter-indication, even for the
descriptionist, in your position, and that is simply that

20 log(Vmeasured / Vreference) = 10 log[(Vmeasured / Vreference)^2],

and that highly suggests that a) we are using the original "bel" (since
the expression involves "10 log()"), and b) we are describing a ratio of
powers (since it involves the ratio of square voltages).

That speaks, I think, to history rather than current practice (pardon the
expression). What you're describing is the way in which engineers adapted a
measurement originally used for power to be useful in a different context,
which is measuring pure voltages using a meter which only responds to
voltage. If we had started with a strictly voltage-defined system, no doubt
the formula for deriving dB would read 10 log(ratio) instead of 20, and
there would be a secondary expression for power where the multiplier was 5.
But that's not how the history happened.

What we're seeing is the aftermath of a historical shift in usage and
real-world practice. Prescriptivists say, "You can't do that!" And
descriptivists say, "I am doing it, and so are a lot of other people." And
again, within their respective frames of reference, both are right. And
wrong.

In any case, decibels have no physical existence; they're a notational
convenience intended to make it easier for intelligent apes (who intuitively
grasp + and - more easily than * and / ) to deal with a sensory apparatus
that works almost exclusively in * and / .

Peace,
Paul

[g]

In article , "Paul Stamler" wrote:
"Randy Yates" wrote in message
...

I will point out one not-so-small counter-indication, even for the
descriptionist, in your position, and that is simply that

20 log(Vmeasured / Vreference) = 10 log[(Vmeasured / Vreference)^2],

and that highly suggests that a) we are using the original "bel" (since
the expression involves "10 log()"), and b) we are describing a ratio of
powers (since it involves the ratio of square voltages).

That speaks, I think, to history rather than current practice (pardon the
expression). What you're describing is the way in which engineers adapted a
measurement originally used for power to be useful in a different context,


How about 100 wats RMS ...



greg

[Eeyore]

Randy Yates wrote:

"Paul Stamler" writes:
wrote in message
Eeyore wrote:

The obsession some peopole have about equating dB
with POWER is utterly ridiculous.

Yes, it's SO ridiculous, it is enshrined in definition. From various
sources, e.g., the ATIS:

dB: Abbreviation for decibel (s). One tenth of the common
logarithm of the ratio of relative powers, equal to 0.1 B
(bel).

dB /= dBu /= dBV /= dBSPL.

How does establishing a reference level make any of these something
other than power?

In the case of dBV the clue is found in the letter V for Volts !

The others are defined by practice.

Graham

[Eeyore]

Mark wrote:

The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

But Randy, you must admit it has now become VERY COMMON PRACTICE to
use dB for Voltage ratios as well.

Not to mention ** SOUND PRESSURE LEVEL ** too !

I can confidently say that the majority of real world uses today for the decibel
involve the 20log10(ratio) equation.

Graham

[Eeyore]

G wrote:

"Paul Stamler" wrote:
"Randy Yates" wrote

I will point out one not-so-small counter-indication, even for the
descriptionist, in your position, and that is simply that

20 log(Vmeasured / Vreference) = 10 log[(Vmeasured / Vreference)^2],

and that highly suggests that a) we are using the original "bel" (since
the expression involves "10 log()"), and b) we are describing a ratio of
powers (since it involves the ratio of square voltages).

That speaks, I think, to history rather than current practice (pardon the
expression). What you're describing is the way in which engineers adapted a
measurement originally used for power to be useful in a different context,

How about 100 wats RMS ...

A joker eh ?

Graham

[Randy Yates]

Mark writes:


The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

But Randy, you must admit it has now become VERY COMMON PRACTICE to
use dB for Voltage ratios as well.

Perhaps you didn't see my previous post about inverse functions.
--
% Randy Yates % "Ticket to the moon, flight leaves here today
%% Fuquay-Varina, NC % from Satellite 2"
%%% 919-577-9882 % 'Ticket To The Moon'
%%%% % *Time*, Electric Light Orchestra
http://www.digitalsignallabs.com

[Randy Yates]

Mark writes:


The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

Maybe? How many authoritative sources do you need to see it defined in
before you concur that it IS a power ratio?

How about if we start tugging on the definition of watt (1
joule/second). "Well, *maybe* it refers to 1 joule / second, but
Webermatic had a manufacturing problem 10 years ago in their power meter
product in which it registered 1.1 joules/second, so now we don't really
know what it means." Or, "John C. PowerEngineer used it for energy in
his report to the DOE 4 years ago and it has now become common practice
that it refers to ENERGY."

Descriptionism in scientific and technical fields leads to chaos.
--
% Randy Yates % "So now it's getting late,
%% Fuquay-Varina, NC % and those who hesitate
%%% 919-577-9882 % got no one..."
%%%% % 'Waterfall', *Face The Music*, ELO
http://www.digitalsignallabs.com

[Mark]

On Oct 24, 3:36 pm, Eeyore
wrote:
Mark wrote:
The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

But Randy, you must admit it has now become VERY COMMON PRACTICE to
use dB for Voltage ratios as well.

Not to mention ** SOUND PRESSURE LEVEL ** too !

I can confidently say that the majority of real world uses today for the decibel
involve the 20log10(ratio) equation.

Graham

maybe real world cases in audio land....
but not true of real world cases in RF land where most things are
power into /out of 50 Ohms

but it is still common enough that it is not consdired a "mistake".

100 Watts RMS is also unfortunatley common but is always a mistake
because it is mathematically incorrect.

Mark



Mark

[Eeyore]

Randy Yates wrote:

Mark writes:

The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

Maybe? How many authoritative sources do you need to see it defined in
before you concur that it IS a power ratio?

How about if we start tugging on the definition of watt (1
joule/second). "Well, *maybe* it refers to 1 joule / second, but
Webermatic had a manufacturing problem 10 years ago in their power meter
product in which it registered 1.1 joules/second, so now we don't really
know what it means."

RUBBISH.

What you describe is merely a calibration error.


Or, "John C. PowerEngineer used it for energy in
his report to the DOE 4 years ago and it has now become common practice
that it refers to ENERGY."

NO. Energy and power are perfectly well defined.


Descriptionism in scientific and technical fields leads to chaos.

You're talking irrelevant nonsense.


Graham

[Eeyore]

Mark wrote:

Eeyore wrote:
Mark wrote:
The trouble lies when common practice and official definition differ.

This is exactly the problem..

Randy may be right, the original __TECHNICAL__ defintion of dB maybe
refers to a power ratio.

But Randy, you must admit it has now become VERY COMMON PRACTICE to
use dB for Voltage ratios as well.

Not to mention ** SOUND PRESSURE LEVEL ** too !

I can confidently say that the majority of real world uses today for the decibel
involve the 20log10(ratio) equation.


maybe real world cases in audio land....
but not true of real world cases in RF land where most things are
power into /out of 50 Ohms

There's lots more of everything else that uses dB than RF alone. And of course using
power related dB measurements only makes any rational sense in matched impedance
circuits which somewhat limits its value.


but it is still common enough that it is not consdired a "mistake".

100 Watts RMS is also unfortunatley common but is always a mistake
because it is mathematically incorrect.

Indeed.

Graham

[Mr.T]

"Randy Yates" wrote in message
...
Descriptionism in scientific and technical fields leads to chaos.

Yes, or maybe it just sorts the technically competent from the technically
illiterate.
As is the case here.

MrT.

[Mike Rivers]

On Oct 24, 5:04 pm, Mark wrote:

maybe real world cases in audio land....
but not true of real world cases in RF land where most things are
power into /out of 50 Ohms

Please note that you're posting to rec.AUIDO.pro and rec.AUDIO.tech.
If you want to talk about RF, please post to rec.RF.bs

100 Watts RMS is also unfortunatley common but is always a mistake
because it is mathematically incorrect.

All right, what's wrong now?

[Mr.T]

"Eeyore" wrote in message
...
NO. Energy and power are perfectly well defined.

Wasn't that his point! No need to accept new definitions caused by incorrect
usage.

MrT.

[Randy Yates]

"Mr.T" MrT@home writes:

"Randy Yates" wrote in message
...
Descriptionism in scientific and technical fields leads to chaos.

Yes, or maybe it just sorts the technically competent from the technically
illiterate.
As is the case here.

And maybe you need to stop having sex with your mother while she's
in between customers.
--
% Randy Yates % "Rollin' and riding and slippin' and
%% Fuquay-Varina, NC % sliding, it's magic."
%%% 919-577-9882 %
%%%% % 'Living' Thing', *A New World Record*, ELO
http://www.digitalsignallabs.com

[Randy Yates]

Eeyore writes:
[...]
Energy and power are perfectly well defined.

Precisely. And so are decibels.
--
% Randy Yates % "So now it's getting late,
%% Fuquay-Varina, NC % and those who hesitate
%%% 919-577-9882 % got no one..."
%%%% % 'Waterfall', *Face The Music*, ELO
http://www.digitalsignallabs.com