[Obedient Drone]

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

[Randy Yates]

"Obedient Drone" writes:

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

I feel your pain. Peace, brother.
--
% Randy Yates % "The dreamer, the unwoken fool -
%% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..."
%%% 919-577-9882 %
%%%% % 'Eldorado Overture', *Eldorado*, ELO
http://home.earthlink.net/~yatescr

[Randy Yates]

Randy Yates writes:

"Obedient Drone" writes:

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

I feel your pain. Peace, brother.

Or sister.
--
% Randy Yates % "I met someone who looks alot like you,
%% Fuquay-Varina, NC % she does the things you do,
%%% 919-577-9882 % but she is an IBM."
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

[fredbloggstwo]

"Obedient Drone" wrote in message
...
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!



You could ask him

"Well I have this bit of wire here with no active elements so it has no
gain, and the signal difference from one end to the other is 0dB" - discuss

Mike

[Eeyore]

Obedient Drone wrote:

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

I'd say he probably knows more about dB than most of your management.

Graham

[[email protected]]

On Jul 29, 12:28 pm, "Obedient Drone" wrote:
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

So, show your manager this:

Since

dB = 10 * log (P1/P2)

i.e. the ratio between two powers, also called "gain",
please ask him to explain his claim that:

0 dB = 10 * log(0)

which, when the right-hand of the equation.

But since the logarithm of 0 is undefined, he's
up his own **** creek without a paddle.

Next, ask him to figure out the followin

Then, ask him to, using the same definition of
dB, calculate the gain G:

0 dB = 10 * log(G)

rearranging, we find that:

G = 10^(dB/10)

G = 10(0/10)

G = 10^0

Now, unless your manager has managed to repeal
some reasonably well established laws of
mathematics, the last time EVERYONE looked,
any number raised to the zeroth power is 1

Of course, as manager, he's right. I have a mortgage
to pay!

See if you can forward this anonymously to your
manager. Please leave my name and email
address in place if you can. Tell him that I would
be more than happy to call him an idiot in the public
space. Tell him, if he'd like, that I'd be happy to
call him an idiot to his face if he insists on this
nonsense.

[Karl Uppiano]

"Obedient Drone" wrote in message
...
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

He obviously did not get to his current management position based on his
technical acumen (or maybe he did - via the Peter Principle). While
annoying, does it impact your day-to-day activities?

[Don Pearce]

On Sun, 29 Jul 2007 20:16:13 GMT, "Karl Uppiano"
wrote:


"Obedient Drone" wrote in message
...
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

He obviously did not get to his current management position based on his
technical acumen (or maybe he did - via the Peter Principle). While
annoying, does it impact your day-to-day activities?


Incompetence is everywhere. Many years ago I had a manager who
rejected a week's calculations with "This is all wrong - voltage dBs
are different to power dBs". I just barely didn't deck him.

d

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

[Roy W. Rising[_2_]]

"Obedient Drone" wrote:
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

"Zero dB" is a reference point for metering. It has been set differently
for various systems. Sometimes it's 0dB = 0VU = +4dBm. Sometimes it's 0dB
= 20dB below digital zero (all ones).

Gain usually is expressed in dB, unity gain is 0dB of gain.

For calculations, dB = 20(log V2/V1) = 10(log P2/P1). I always enjoy
pointing out that a 100W power amp has only 3dB more output than one with
50 watts.

--
~ Roy
"If you notice the sound, it's wrong!"

[jim Gregory]

0dB - as a comparison - is a way of saying no gain (nor loss) exists between
i/p and o/p of an active stage when there is a measurable level at a known
freq across its i/p, or there's a voltage gain of 1 - but if noticing no
signal is present at the same o/p when the i/p is still driven (due to no DC
or a fault), it would
indicate a huge loss, ie, neg many dBs.

You cannot talk about a 0dB o/p if/because the i/p is nil. All you can
measure/hear
is the system noise.

However, when measuring amp ihd, thd, noise, hum.... 0dB is the arbitrary
reference level that is quoted, being so many mV or V AC, at a known freq
within
passband, into a specified, acceptable load.
Usually the sinewave test signal is set up for amp in linear behaviour,
10-12dB below o/p clipping point,.ie, 10-12dB in hand. The stages' gain
hypothetically is +26dB, or a V factor of 20x.
The i/p level can be increased in steps of 2dB and the parameters at the o/p
should increase proportionately [until onset of non-linearity].
Meantime that o/p level has moved up from 0dB, yet the apparatus gain factor
has
remained the same.

"Obedient Drone" wrote in message
...
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

[Les Cargill]

Obedient Drone wrote:

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!




0 dB acoustic power would be no signal (passing); 0 dB on a VU
meter on a console would be unity gain.

It is an incomplete question, in other words. 0 dB relative
to what?

--
Les Cargill

[Eeyore]

Karl Uppiano wrote:

"Obedient Drone" wrote

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

He obviously did not get to his current management position based on his
technical acumen (or maybe he did - via the Peter Principle). While
annoying, does it impact your day-to-day activities?

I was amazed a couple of years back to discover that the alleged 'technical
manager' at the company I designed for believed that high bit rate mp3 had a
higher bit rate than uncompressed CD audio. Talk about 'not getting it'.

Mind you, he had a lot of funny ideas, all seemingly based on
'half-understandings' (or half-misunderstandings perhaps) and popular folklore.

Graham

[[email protected]]

On Jul 29, 7:11 pm, Les Cargill wrote:
Obedient Drone wrote:
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

0 dB acoustic power would be no signal (passing);

If you mean 0 dB SPL, you'd be wrong. It's be the equivalent
of 10^12 W/cm^2, by definition.

0 dB on a VU meter on a console would be unity gain.

No, it wouldn't. it would whatever the system gain structure
makes it.

It is an incomplete question, in other words. 0 dB relative
to what?

The original poster was QUITE complete:

"0 db, previously thought equivalent to unity gain, ..."

That is, 20 log(Vout/Vin). That's a complete question
that needs not further qualification to render a valid,
consistent answer. The key here is "gain," this the
reference is defined as the input signal level, whatever
that level may be: we don't have to know that level.

[Eeyore]

Don Pearce wrote:

"Karl Uppiano" wrote:
"Obedient Drone" wrote

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

He obviously did not get to his current management position based on his
technical acumen (or maybe he did - via the Peter Principle). While
annoying, does it impact your day-to-day activities?

Incompetence is everywhere. Many years ago I had a manager who
rejected a week's calculations with "This is all wrong - voltage dBs
are different to power dBs". I just barely didn't deck him.

The worst of it Don is that the level of imcompetence and the arrogance of its
owners in applying it seems to be on the increase. The dumbing down of education
and reduced skills, especially numeric and scientific that politicians have
forced on us has to be very largely involved.

The 'MBA culture' where it's alleged that a 'professional manager' can run your
business better without any background knowledge of or respect for how it
operates is a goodie too.

I well recall when Studiomaster employed some ex-Tektronix managers to run the
manufacturing operation. I was dismayed when one of them ran a 3 month project
to *add a zero to all part numbers* components, assemblies, sub-assemblies, you
name it. He insisted they needed an extra character 'in case a aprt needed to be
re-specced'. The idea being that the trailing zero he'd added could be amended
to 1,2 3 etc depending on revision level ! WTF ! The idea was used ONCE

But there's much worse.. Their manufacturing operating was pretty second-rate,
seemingly using the cheapest labour money could buy. They had several ppl who
were functionally illiterate for example, something I've never seen in any other
company. What held it together was simply fairly thorough Q/C at the end of the
line (there was also decent outsourced pcb assembly) and that Q/C was mainly
down to 2 guys who simply liked to make sure that stuff worked properly and they
wouldn't let it through if it didn't.

Now, I recall one of these ex-Tek 'engineer-managers' asking me one day if it
would help if we used that Japanese Taguchi method to improve quality.
http://en.wikipedia.org/wiki/Taguchi_methods

I was simply dumbstruck that he couldn't see the obvious simply in front of his
own eyes. I guess they don't teach his ilk to understand basic manufacturing
principles any more. Just ensuring the right temperature profile was used for
soldering certain assemblies would have helped. There was one that was
notoriously prone to genuine *cold* joints that was fixed by using a Weller 800F
tip for soldering power devices into place instead of 700, but they preferred
700F tips 'because they last longer' and it seems they crept back into use after
I'd originally identified the problem. Just this one thing alone was responsible
for a host of returns.

Jeez. It DOES make me want to give up actually. It's like rolling rocks uphill
and you rarely get any thanks for it on account of the number of noses belonging
to rank idiots (who should never even be there in the first place) you have to
put out of joint in the process.

Graham.

[Eeyore]

"Roy W. Rising" wrote:

"Obedient Drone" wrote:
0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

"Zero dB" is a reference point for metering. It has been set differently
for various systems. Sometimes it's 0dB = 0VU = +4dBm.

+4dBu please ! :-)


Sometimes it's 0dB = 20dB below digital zero (all ones).

Gain usually is expressed in dB, unity gain is 0dB of gain.

The idiot manager at Studioamster had some odd ideas about gain. Seemingly he'd
do tests and come back with results different to mine. He might even tweak a
component value during a prototype stage and I'd have to tweak it back. I found
out what it was in the end.

This guy thought, say with a mic amp, that if you put -60dBu into a mic amp, it
had 60dB gain if the output was *0 VU* ! His rationale was this was 'zero on the
meter'. In fact his entire idea of gain included this dBu/dBVU factor , i.e.a
spurious 4dB ! When I expalined that gain was simply the ratio of output to
input levels he just didn't get it and even implied he rejected the explanation.



For calculations, dB = 20(log V2/V1) = 10(log P2/P1). I always enjoy
pointing out that a 100W power amp has only 3dB more output than one with
50 watts.

And yet lots of ppl will give you a blank look and refuse to believe 100W isn't
'twice as loud' as 50W.

Graham

[Roy W. Rising[_2_]]

Eeyore wrote:
"Roy W. Rising" wrote:


"Zero dB" is a reference point for metering. It has been set
differently for various systems. Sometimes it's 0dB = 0VU = +4dBm.

+4dBu please ! :-)

You're welcome to add "Sometimes it's 0dB = +4dBu" if that's what *pleases*
you, but sometimes it's been +8dBm as well ... and that in a 150ohm
environment! ;-)

Sometimes it's 0dB = 20dB below digital zero (all ones).

Gain usually is expressed in dB, unity gain is 0dB of gain.

The idiot manager at Studioamster had some odd ideas about gain.
Seemingly he'd do tests and come back with results different to mine. He
might even tweak a component value during a prototype stage and I'd have
to tweak it back. I found out what it was in the end.

This guy thought, say with a mic amp, that if you put -60dBu into a mic
amp, it had 60dB gain if the output was *0 VU* ! His rationale was this
was 'zero on the meter'. In fact his entire idea of gain included this
dBu/dBVU factor , i.e.a spurious 4dB ! When I expalined that gain was
simply the ratio of output to input levels he just didn't get it and even
implied he rejected the explanation.

A friend explains it by saying "Sh*t seems to float to the top".

For calculations, dB = 20(log V2/V1) = 10(log P2/P1). I always enjoy
pointing out that a 100W power amp has only 3dB more output than one
with 50 watts.

And yet lots of ppl will give you a blank look and refuse to believe 100W
isn't 'twice as loud' as 50W.

Graham

--
~ Roy
"If you notice the sound, it's wrong!"

[Eeyore]

Les Cargill wrote:

Obedient Drone wrote:

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

0 dB acoustic power would be no signal (passing);

No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.


0 dB on a VU meter on a console would be unity gain.

A meter reading is not a gain. It's a signal level.


It is an incomplete question, in other words. 0 dB relative
to what?

The first thing you wrote that made any sense. Now go back to school and learn
to get the rest right.

Graham

[Eeyore]

wrote:

Les Cargill wrote:

It is an incomplete question, in other words. 0 dB relative
to what?

The original poster was QUITE complete:

"0 db, previously thought equivalent to unity gain, ..."

That is, 20 log(Vout/Vin). That's a complete question
that needs not further qualification to render a valid,
consistent answer. The key here is "gain," this the
reference is defined as the input signal level, whatever
that level may be: we don't have to know that level.

Correct. I missed that one. Gain, being simply a ratio has no units and
therefore is shown as dB with no suffix.

Signal levels of course require the identifying unit to be stated, although
(sloppily) it's often forgotten for SPL measurements that should be for
example X dB(A) -where it's an A weighted measurement- SPL.

Graham

[Eeyore]

"Roy W. Rising" wrote:

Eeyore wrote:
"Roy W. Rising" wrote:

"Zero dB" is a reference point for metering. It has been set
differently for various systems. Sometimes it's 0dB = 0VU = +4dBm.

+4dBu please ! :-)

You're welcome to add "Sometimes it's 0dB = +4dBu" if that's what *pleases*
you, but sometimes it's been +8dBm as well ... and that in a 150ohm
environment! ;-)

I'm pointing out that dBu =/= dBm. Almost nothing uses dBm any more in pro audio
and hasn't done for about 40 years. dBm is a POWER, and dBu is a VOLTAGE. A VU
meter measures voltage not power. We do not 'impedance amtch' audio circuits for
maximum power transfer these days and the dBm died with that.

Just show me one piece of modern kit with 150 ohm output Z and 150 ohm input Z !

Graham

[William Sommerwerck]

Well, not really...

I just came in on this, so if I'm repeating something, I apologize.

0dB, as someone else pointed out, is a specific, arbitrary power level. It
has nothing to do with gain, per se; it is a reference point for gain
_changes_.

Also, a device can have a _voltage_ gain or loss, yet have a _power_ gain of
0dB.

[Randy Yates]

"William Sommerwerck" writes:

Well, not really...

I just came in on this, so if I'm repeating something, I apologize.

0dB, as someone else pointed out, is a specific, arbitrary power level. It
has nothing to do with gain, per se; it is a reference point for gain
_changes_.

I haven't seen it used that way in my 28 years of engineering. Usually
when you see a "dB" value without any units, such as "10 dB", and it's
in reference to a two-port device, it is assumed that it is the power
at the output port relative to the power at the input port. That is,
the gain of the device.

On the other hand, a dB value with an associated suffix, such as
"0 dB SPL," is not a gain but an absolute power level.
--
% Randy Yates % "I met someone who looks alot like you,
%% Fuquay-Varina, NC % she does the things you do,
%%% 919-577-9882 % but she is an IBM."
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

[Les Cargill]

Eeyore wrote:


Les Cargill wrote:


Obedient Drone wrote:


0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

0 dB acoustic power would be no signal (passing);


No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.


0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.



0 dB on a VU meter on a console would be unity gain.


A meter reading is not a gain. It's a signal level.



A gain may be inferred *from* a signal level. It's
not that hard a leap. The terms are often used
interchangeably, since there's a nice functional
map between them.


It is an incomplete question, in other words. 0 dB relative
to what?


The first thing you wrote that made any sense. Now go back to school and learn
to get the rest right.


Tch. Whadda thread.

Graham


--
Les Cargill

[Eeyore]

Randy Yates wrote:

"William Sommerwerck" writes:

Well, not really...

I just came in on this, so if I'm repeating something, I apologize.

0dB, as someone else pointed out, is a specific, arbitrary power level. It
has nothing to do with gain, per se; it is a reference point for gain
_changes_.

I haven't seen it used that way in my 28 years of engineering. Usually
when you see a "dB" value without any units, such as "10 dB", and it's
in reference to a two-port device, it is assumed that it is the power
at the output port relative to the power at the input port. That is,
the gain of the device.

It's very rare in audio for it to be a measure of power. It's almost invariably
a VOLTAGE gain that's stated.

Indeed you can't make any meaningful measure of power gain unless the input and
output impedance are known (are usually the same such as the deprecated use of
600 ohms) and are explicitly specified.


On the other hand, a dB value with an associated suffix, such as
"0 dB SPL," is not a gain but an absolute power level.

Actually, that's a *sound pressure level* that's why it's abbreviated to SPL,
which is a pressure measured in units of Pascals (Newtons/sq metre) not a power
level measured in units of watts ! Sorry to have to be so pedantic but these
mistakes are all too common.

http://en.wikipedia.org/wiki/Sound_pressure
http://en.wikipedia.org/wiki/Sound_power

We use dB SPL normally for acoustic measurements, the pressure measurement not
the power.

Graham

[Eeyore]

Les Cargill wrote:

Eeyore wrote:
Les Cargill wrote:
Obedient Drone wrote:

0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

0 dB acoustic power would be no signal (passing);


No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.

0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.

Utter and total NONSENSE !

What exactly do you think is unattainable about it ?

Graham

[Eeyore]

Les Cargill wrote:

Eeyore wrote:
Les Cargill wrote:

0 dB on a VU meter on a console would be unity gain.

A meter reading is not a gain. It's a signal level.

A gain may be inferred *from* a signal level.

It can be CALCULATED actually.


It's not that hard a leap. The terms are often used
interchangeably, since there's a nice functional
map between them.

No, there's no excuse to use the terms interchangeably since it results in
misunderstandings that seem all too common as is coming out in this thread. Notably
there's the likely confusion with 0dBu and 0VU which is a significant error.

You might as well say you can measure distance in ounces.

Graham

[Eeyore]

Les Cargill wrote:

Eeyore wrote:
Les Cargill wrote:

0 dB acoustic power would be no signal (passing);

No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.

0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.

How you think hearing tests work btw ?

0dB SPL is only the *average* threshold of hearing for humans anyway. Actually, that
would be 0 phons, not dB SPL in fact ( the human ear has a frequency response that
is anything but flat at low levels).

http://en.wikipedia.org/wiki/Phon

You can see that the treshold of audibility @ 25Hz for example is ~ 65dB SPL.

Note that the threshold of audibilty @ 4kHz is ~ -6dB SPL. Yes, that's a minus in
front of the 6 there. So much for even 0dB being 'unattainable' !

Graham

[Randy Yates]

Eeyore writes:

Randy Yates wrote:

"William Sommerwerck" writes:

Well, not really...

I just came in on this, so if I'm repeating something, I apologize.

0dB, as someone else pointed out, is a specific, arbitrary power level. It
has nothing to do with gain, per se; it is a reference point for gain
_changes_.

I haven't seen it used that way in my 28 years of engineering. Usually
when you see a "dB" value without any units, such as "10 dB", and it's
in reference to a two-port device, it is assumed that it is the power
at the output port relative to the power at the input port. That is,
the gain of the device.

It's very rare in audio for it to be a measure of power. It's almost invariably
a VOLTAGE gain that's stated.

I don't disagree that it's voltage gain, but the underlying thing
being represented when a decibel specification is used is
power. That's why voltage gain is 20*log10(V2/V1) and not
10*log(V2/V1) (see [sedra] for an example definition). Yes, there
needs to be an impedance specified or understood.

Actually, that's a *sound pressure level* that's why it's abbreviated to SPL,
which is a pressure measured in units of Pascals (Newtons/sq metre) not a power
level measured in units of watts !

They are one-to-one (just as, when impedance is known, voltage and power
are in a one-to-one correspondence). See, e.g., Figure 2.1, p.17, in
[Zwicker], in which he plots minimum and maximum human auditory thresholds
in both sound pressure level and sound intensity level units in one graph.

Sorry to have to be so pedantic but these mistakes are all too
common.

There is no mistake. But I can appreciate that you're being careful.

http://en.wikipedia.org/wiki/Sound_pressure
http://en.wikipedia.org/wiki/Sound_power

By the way, I no longer honor wikipedia as a reference source. It's too
unstable.

--Randy

@BOOK{sedra,
title = "{Microelectronic Circuits}",
author = "Adel~S.~Sedra and Kenneth~C.~Smith",
publisher = "Saunders College Publishing",
edition = "third",
year = "1991"}

@BOOK{psychoacoustics,
title = "{Psychoacoustics: Facts and Models}",
author = "E.~Zwicker and H.~Fastl",
publisher = "Springer",
edition = "second",
year = "1999"}

--
% Randy Yates % "The dreamer, the unwoken fool -
%% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..."
%%% 919-577-9882 %
%%%% % 'Eldorado Overture', *Eldorado*, ELO
http://home.earthlink.net/~yatescr

[Chris Hornbeck]

On Sun, 29 Jul 2007 22:14:49 -0400, Les Cargill
wrote:

Absolutely NEVER is 0dB *no signal*.


0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.

Wait! Stop! Everybody please just STOP saying "dB". Right
now and I mean it. Do I have to call your mother?

Better.

Now. A Bel is the log of the ratio of two powers.


There is *no other* meaning.

Every other *******ized meaning grafted onto this pure
and holy definition needs to be very carefully defined.
Anything less and you'll end up with the (well deserved)
mess that this thread has become.


Thanks, and, keep it clean out there,

Chris Hornbeck
"I would much rather be able to say it sounds like such and such, but
when it's not obvious distortion and/or noise, when the specs are really
good for those factors and IM and slew rate and a host of other stuff I
probably can't bring to consciousness right now, yet one preamp lets me
hear as if the source is alive and right there, and the next one makes
me feel as if I'm listening to the equivalent of a very detailed
cardboard Elvis, I don't know what words to offer that might help. But
hell, I'm willing to try. Everything we might like to know isn't known
yet, and through history people have come up with ways to measure stuff
that previously went unmeasured." - Hank Alrich 07 May 2005

[Roy W. Rising[_2_]]

Eeyore wrote:
"Roy W. Rising" wrote:

Eeyore wrote:
"Roy W. Rising" wrote:

"Zero dB" is a reference point for metering. It has been set
differently for various systems. Sometimes it's 0dB = 0VU = +4dBm.

+4dBu please ! :-)

You're welcome to add "Sometimes it's 0dB = +4dBu" if that's what
*pleases* you, but sometimes it's been +8dBm as well ... and that in a
150ohm environment! ;-)

I'm pointing out that dBu =/= dBm. Almost nothing uses dBm any more in
pro audio and hasn't done for about 40 years. dBm is a POWER, and dBu is
a VOLTAGE. A VU meter measures voltage not power. We do not 'impedance
amtch' audio circuits for maximum power transfer these days and the dBm
died with that.

Just show me one piece of modern kit with 150 ohm output Z and 150 ohm
input Z !

Graham

My comments were about the importance of "Zero dB" as a *reference*. I
gave examples of several different things to which this reference can be
applied. In each case I said "sometimes". My experience ranges from when
impedance *matching* was the rule, through the wonderful advent of
near-zero source impedances coupled to essentially non-reactive bridging
inputs. A depth of understanding of these relationships leads me to
chuckle about many enduring arguments in this place. Obsolescent vacuum
tube condenser mics that "prefer" inductive preamp inputs are humorous. I
prefer modern mics that care little about their load.

Nonetheless, the dBm lives on. Universal Audio, for reasons never to be
understood, reissued the venerable LA-2 and LA-3A in their exact original
forms. The latter was developed to drive a matching 150 or 600 ohm load.
When it's output is not loaded, it's frequency response is nonlinear.

If I had made the box, it would be significantly more quiet and definitely
not subject to incorrect loading. ;-)

--
~ Roy
"If you notice the sound, it's wrong!"

[Eeyore]

"Roy W. Rising" wrote:

Nonetheless, the dBm lives on.

Fairly pointlessly in audio. I abhor seeng its continued use when ppl really
mean dBu and they'd not have the first clue about connecting impedance matched
circuits properly.


Universal Audio, for reasons never to be understood, reissued the venerable
LA-2 and LA-3A in their exact original
forms.

I'd say one could understand that fairly easily actually. They wanted it to be
authentic presumably, warts and all.


The latter was developed to drive a matching 150 or 600 ohm load.
When it's output is not loaded, it's frequency response is nonlinear.

If I had made the box, it would be significantly more quiet and definitely
not subject to incorrect loading. ;-)

But then it wouldn't be an LA-2/3A !

Graham

[Les Cargill]

Eeyore wrote:


Les Cargill wrote:


Eeyore wrote:

Les Cargill wrote:

Obedient Drone wrote:


0 db, previously thought equivalent to unity gain, is actually
a gain of 0.0 (no signal passes) according to my manager
at a major audio company in the San Francisco Bay Area.

Of course, as manager, he's right. I have a mortgage
to pay!

0 dB acoustic power would be no signal (passing);


No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.

0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.


Utter and total NONSENSE !

What exactly do you think is unattainable about it ?


What, the nonsense or the 0dB SPL level?

I think that the occurrance of actual 0 dB situations in
real life in air is all but nonexistent. 10 dB is very,
very quiet.

Graham


Backing up a bit - I suspect these people have miscommunicated,
and we're doing a fine job of continuing that. Cheers.

--
Les Cargill

[Les Cargill]

Eeyore wrote:


Les Cargill wrote:


Eeyore wrote:

Les Cargill wrote:


0 dB acoustic power would be no signal (passing);

No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.

0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.


How you think hearing tests work btw ?

0dB SPL is only the *average* threshold of hearing for humans anyway. Actually, that
would be 0 phons, not dB SPL in fact ( the human ear has a frequency response that
is anything but flat at low levels).

http://en.wikipedia.org/wiki/Phon

You can see that the treshold of audibility @ 25Hz for example is ~ 65dB SPL.

Note that the threshold of audibilty @ 4kHz is ~ -6dB SPL. Yes, that's a minus in
front of the 6 there. So much for even 0dB being 'unattainable' !

Graham



I had been operating under the "you never find an SPL level
lower than 10dB" assumption for quite a while now. Innaresting.

--
Les Cargill

[Eeyore]

Les Cargill wrote:

Eeyore wrote:
Les Cargill wrote:
Eeyore wrote:
Les Cargill wrote:

0 dB acoustic power would be no signal (passing);

No. 0dB SPL (to give it it's correct name) would be a sound pressure level of
2x10^-5 Pa.
http://en.wikipedia.org/wiki/Sound_pressure

Absolutely NEVER is 0dB *no signal*.

0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.


How you think hearing tests work btw ?

0dB SPL is only the *average* threshold of hearing for humans anyway. Actually, that
would be 0 phons, not dB SPL in fact ( the human ear has a frequency response that
is anything but flat at low levels).

http://en.wikipedia.org/wiki/Phon

You can see that the treshold of audibility @ 25Hz for example is ~ 65dB SPL.

Note that the threshold of audibilty @ 4kHz is ~ -6dB SPL. Yes, that's a minus in
front of the 6 there. So much for even 0dB being 'unattainable' !


I had been operating under the "you never find an SPL level
lower than 10dB" assumption for quite a while now. Innaresting.

10dB SPL is indeed very quiet. In true 'soundproof rooms' you can do better though.
Anechoic chambers are pretty weird like that.

Graham

[[email protected]]

On Jul 29, 10:24 pm, Eeyore
wrote:

You might as well say you can measure distance in ounces.

ahh new song lyrics

I load sixteen miles and what do I get...
or
lord I see 100 grams

opps the last one got busted.....

[Adrian Tuddenham]

Chris Hornbeck wrote:


Now. A Bel is the log of the ratio of two powers.


There is *no other* meaning.

Hooray! Accuracy at last.

I have recently had great difficulty explaining this to someone who
thought that a transformer gave 'gain' whereas an emitter-follower
didn't.



[If you want to be absolutely beyond doubt, you could add that it is Log
to the base 10, just in case someone supposes otherwise]
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[Eeyore]

Adrian Tuddenham wrote:

Chris Hornbeck wrote:

Now. A Bel is the log of the ratio of two powers.

There is *no other* meaning.

Hooray! Accuracy at last.

I have recently had great difficulty explaining this to someone who
thought that a transformer gave 'gain' whereas an emitter-follower
didn't.

A transformer is entirely capable of giving voltage gain.

Graham

[[email protected]]

On Jul 29, 10:14 pm, Les Cargill wrote:

0dB is an unatainable acoustic SPL level meaning
the threshold of audibility. That means "no signal"
for all intents and purposes.

Uhm, no, emphatically so at that.

0 dB SPL refers to an AVERAGE threshold sound pressure
level achieved during a rather extensive set of testing over
a half century ago. It is the NORMALIZED average threshold
at 1 kHz. In fact, the average curve shows the threshold
lower by 6 dB at 4 kHz in most test subjects. That alone
puts false your claim that 0dB SPL is "unnattainable."

Secondly, the notion that 0 dB SPL means "no signal
for all intents and purposes" is simply nonsense. That
figure is achieved over the measurement or detection
bandwidth and represents the ability to differentiate
the signal form the noise. Narrow the detection
bandwidth, and immediately that threshold lowers. The
ear represents (approximately) a 1/3 octave-wide filter
at medium and high frequencies: simply narrow that
bandwidth and you can easily detect signals lower.

Now, one may argue that you can't "narrow the
bandwidth" of the ear. That, however, belies your
broad, blanket claim of "no signal, for ALL intents
and purposes."

And, lastly, your premise that 0 dB represents NO signal
is simply false on its face. Once again, look at the
definition:

dB = 10 * log (P1/P2)

and if you have 0 dB, then P1/P2 must be equal to
one.

In most instances I and most people are aware of,
"no signal" means "0 signal", and 0 is not equal to 1.

[Roy W. Rising[_2_]]

Eeyore wrote:
"Roy W. Rising" wrote:

Nonetheless, the dBm lives on.

Fairly pointlessly in audio. I abhor seeng its continued use when ppl
really mean dBu and they'd not have the first clue about connecting
impedance matched circuits properly.

Universal Audio, for reasons never to be understood, reissued the
venerable LA-2 and LA-3A in their exact original
forms.

I'd say one could understand that fairly easily actually. They wanted it
to be authentic presumably, warts and all.

The latter was developed to drive a matching 150 or 600 ohm load.
When it's output is not loaded, it's frequency response is nonlinear.

If I had made the box, it would be significantly more quiet and
definitely not subject to incorrect loading. ;-)

But then it wouldn't be an LA-2/3A !

Graham

I agree about the abuse of dBm when dBu is correct.

I once modified some LA-3As to avoid the noisy active main chain while
maintaining the side chain to drive the T4B. It resulted in an easily
recovered 6dB insertion loss with NO internal noise. I labeled it the
"LA-Too" ;-)

--
~ Roy
"If you notice the sound, it's wrong!"

[jim Gregory]

I had said 0dB could be "the arbitrary reference level".and not "a specific,
arbitrary power level".
[This datum reference voltage and later changes would be measured by an
audio millivoltmeter and not a Power meter.]
In 40+ years of studios maintenance/design I rarely measured Watts rms as I
usually
dealt with voltage amplifiers.
Maybe I did, but around a mW when o/p @ '0' level was terminated in 600 Ohm.

An earlier writer Don said, that his boss once opined that "voltage dBs are
different to power dBs"?
Hmmm!
Jim

"William Sommerwerck" wrote in message
. ..
Well, not really...

I just came in on this, so if I'm repeating something, I apologize.

0dB, as someone else pointed out, is a specific, arbitrary power level. It
has nothing to do with gain, per se; it is a reference point for gain
_changes_.

Also, a device can have a _voltage_ gain or loss, yet have a _power_ gain
of
0dB.

[Mr.T]

"jim Gregory" wrote in message
...
In 40+ years of studios maintenance/design I rarely measured Watts rms as
I
usually dealt with voltage amplifiers.

I'd be more surprised if you HAD measured "watts RMS" !
:-)

MrT.