PSU for precision audio opamps

[Dirk Bruere at NeoPax]

So no resistor value above about ~ 470 ohms ? (sorry just guessing there,
I didn't fancy doing the sums).

You could quote them the 4562's THD figure. That'll blow 'em sideways.

Why the 4562 btw as opposed to the newer LME497x0 range ?

No particular reason, but it's better than the stuff driving it by a
long way.

 

[Dirk Bruere at NeoPax]

Where would you get a signal that good? Or a quiet-enough place to
listen to it?

Do you stop breathing when you listen to stuff like that?

Try putting it through a 3kW amp and then sticking your head close to
the speakers.

 

[Eeyore]

Try putting it through a 3kW amp and then sticking your head close to
the speakers.

I sort of did something similar to that once.

**** it hurt.

Graham

 

[Fred Bartoli]

Eeyore a écrit :

I sort of did something similar to that once.

Eh eh, why did I knew that?

 

[JosephKK]

Tell me about it. I hear it all the time.


How loud have YOU gone ?

Easily 130dB here (at v. low THD).

Is there any other human sense that can cover that much range ?

Graham

A little excessive snipping? 140+ dB vision, upwards of 240 dB sense
of smell?

 

[JosephKK]

Well, the only PSU I have is that of a PC.
So how do audio cards like the Auzentech that boast 120dB s/n ratios
handle their supplies?

Dirk

Gosh, you don't think that they might lie? (advertise a theoretical
capability based on datasheet spec's.)

 

[Tim Williams]

A little excessive snipping? 140+ dB vision, upwards of 240 dB sense
of smell?

I don't buy it. But then, are we talking humans specifically, or any animal
at all? For sure, a simple sanity check will show that a whopping 240dB is
impossible (1 mole = 6 x 10^_23_ molecules).

I don't think humans can detect single molecules. Finding information on
this is amazingly difficult, but one reference:
http://makingscents.typepad.co.uk/making_scents/2007/04/the_worlds_smel.html
states 0.1 ppt, or -130dB concentration. Mind, this is one blog reference,
on one molecule, in humans. This is not a good start. It is true that most
mercaptans are sensible on the ppt level by humans.

On the top end of the scale, many molecules have no smell, so naievely one
might assume the range is at least -130 to 0dB, roughly speaking. But I
suspect the sense of smell saturates much sooner than "0dB". Some odors are
weaker, perhaps in the parts per thousand range (I know matter-of-factly
that pure propane gas has a very mild odor), putting the ceiling at
perhaps -20 or -30dB, but that's measuring a completely different
molecule -- comparing odor thresholds is NOT comparing threshold to
saturation! For sure, the sense of smell fatigues after being exposed to an
odor, giving some limit to dynamic range over time at least. Unfortunately,
I doubt I could find any data on how strong a smell can be sensed.

Elsewhere, bloodhounds are mentioned as up to 100 million times (70dB) more
sensitive than humans (again, on completely unspecified terms!), putting
their sense down around perhaps -200dB. Now, one [human] breath of air
contains a couple liters volume, which is about 0.1 mole of air, or 6 x
10^22 molecules. That means humans can smell, per breath, about 6 billion
molecules of that grapefruit stuff. That also means bloodhounds can smell
on the order of hundreds or tens of molecules, which is quite impressive.
The most sensitive insects supposedly can detect single molecules, which is
even more impressive (all in the name of sex, of course).

Vision has a wide range, but I wouldn't put that much confidence in human
vision. After adjusting, our eyes can maybe see some details on a moonless
night, which Wikipedia gives as 1mlx. Our eyes really evolved to cope with
direct sunlight, which pretty well maxes them out at 100k lux. That's a
range of 80dB. Very little detail can be seen in that darkness, not even
color, and it takes a half hour to adapt to those conditions, so it's not a
very useful range for the first 20 or 30dB.

Tim

 

[Dirk Bruere at NeoPax]

Gosh, you don't think that they might lie? (advertise a theoretical
capability based on datasheet spec's.)

http://tinyurl.com/5l8xsm

 

[Dirk Bruere at NeoPax]

A little excessive snipping? 140+ dB vision, upwards of 240 dB sense
of smell?

I don't buy it. But then, are we talking humans specifically, or any animal
at all? For sure, a simple sanity check will show that a whopping 240dB is
impossible (1 mole = 6 x 10^_23_ molecules).

I don't think humans can detect single molecules. Finding information on
this is amazingly difficult, but one reference:
http://makingscents.typepad.co.uk/making_scents/2007/04/the_worlds_smel.html
states 0.1 ppt, or -130dB concentration. Mind, this is one blog reference,
on one molecule, in humans. This is not a good start. It is true that most
mercaptans are sensible on the ppt level by humans.

On the top end of the scale, many molecules have no smell, so naievely one
might assume the range is at least -130 to 0dB, roughly speaking. But I
suspect the sense of smell saturates much sooner than "0dB". Some odors are
weaker, perhaps in the parts per thousand range (I know matter-of-factly
that pure propane gas has a very mild odor), putting the ceiling at
perhaps -20 or -30dB, but that's measuring a completely different
molecule -- comparing odor thresholds is NOT comparing threshold to
saturation! For sure, the sense of smell fatigues after being exposed to an
odor, giving some limit to dynamic range over time at least. Unfortunately,
I doubt I could find any data on how strong a smell can be sensed.

Elsewhere, bloodhounds are mentioned as up to 100 million times (70dB) more
sensitive than humans (again, on completely unspecified terms!), putting
their sense down around perhaps -200dB. Now, one [human] breath of air
contains a couple liters volume, which is about 0.1 mole of air, or 6 x
10^22 molecules. That means humans can smell, per breath, about 6 billion
molecules of that grapefruit stuff. That also means bloodhounds can smell
on the order of hundreds or tens of molecules, which is quite impressive.
The most sensitive insects supposedly can detect single molecules, which is
even more impressive (all in the name of sex, of course).

Vision has a wide range, but I wouldn't put that much confidence in human
vision. After adjusting, our eyes can maybe see some details on a moonless
night, which Wikipedia gives as 1mlx. Our eyes really evolved to cope with
direct sunlight, which pretty well maxes them out at 100k lux. That's a
range of 80dB. Very little detail can be seen in that darkness, not even
color, and it takes a half hour to adapt to those conditions, so it's not a
very useful range for the first 20 or 30dB.

Tim

The Human eye can detect down to around 100 photons per 100mS
http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
That, for Green light, is around 4.10^-16 Watts over an area of approx
10^-5 sq m (pupil size) for a power of 4.10^-11 W/sq m

At the upper end we have 1kW/sq m bright sunlight which gives a dynamic
range of approx 14 orders of magnitude.

Unless I've dropped some zeros somewhere...

 

[JosephKK]

http://tinyurl.com/5l8xsm

Now if only my ears were nearly as fancy as that test equipment.

 

[Dirk Bruere at NeoPax]

Is that the way you listen to music?

To some extent.
When I sit next to the speakers I don't want to hear a loud hissing
sound during what should be silence.

 

[Eeyore]

A little excessive snipping? 140+ dB vision,

Is it that much ?

upwards of 240 dB sense of smell?

Dogs ? I thought ours was quite limited.

Graham

 

[Eeyore]

http://tinyurl.com/5l8xsm

Errr ...... That's -130dB / Hz or whatever, It's not well explained what the measuring
bandwidth is.

That's ~ -87dB (20Hz-20kHz unweighted).

Nothing special really. I'm sure I can do better.

I'm surprised you don't understand audio measurements properly. If they can't get that
right, then the rest of it is frankly a load of wank.

Graham

 

[Eeyore]

Dirk Bruere at NeoPax

Is that the way you listen to music?

I could tell you a story about that.

Graham

 

[Eeyore]

Now if only my ears were nearly as fancy as that test equipment.

Those figures are nonsense and completely misrepresented as might be expected from the PC
/ consumer audio press.

Graham

 

[Eeyore]

Where does the silence come from?

It's not hard to get studios down to ~ 10-12dB. Been in them.

Certainly not from the true source
material, which I presume was created by real people in real places,
using real microphones.

Good condenser mics can achieve something like15-18dB equivalent acoustic
noise (or less even ?). Not sure offhand how good dynamics can go. Close
miking helps.

I guess the silence is artificially created in
the studio process of synthesizing the commercial recordings.

Peaking at maybe 130dB for even for an orchestra with no amplification.

That's 115dB dynamic range easily. Hah, and you think 16 bit is adequate ?

Graham

 

[Eeyore]

Hell, 6N copper wire isn't "adequate" to some people.

People in the PRO audio trade don't have anything to do with that kind of
fuckwittery.

You might as well compare an MD with a faith healer.

Graham

 

[JosephKK]

Is it that much ?



Dogs ? I thought ours was quite limited.

Graham

It seems i over estimated sense of smell. Vision seems to be about
correct, the adaptation range is huge, and the fundamental sensitivity
fabulous.

 

[Eeyore]

It seems i over estimated sense of smell. Vision seems to be about
correct, the adaptation range is huge, and the fundamental sensitivity
fabulous.

I agree about the visual adaptation, but the sensory quality at low lux falls
off markedly, not least requiring significant adaption time, the use of red
goggles etc.

In practical everyday use, I reckon our audible skills are the ones that
routinely return the widest dynamic range though. I certainly rate mine
anyway.

Graham

 

[Eeyore]

To some extent.
When I sit next to the speakers I don't want to hear a loud hissing
sound during what should be silence.

I find no trouble *whatever* designing pro-audio that confortably fulfils
those criteria. Consumer audio with its inherently highly limited unbalanced
connections and regularly indifferent design is another kettle of fish.
Chasing down the last hums and buzzes is the bugger though.

I a recent real case, I traced some monitor speaker buzz (best audible by the
ear to the speaker trick but still annoying at a normal listening distance)
to some shockingly EMC incompliant internal equipment wiring (the classic
'Pin 1 problem' wrt XLR connectors) for those faimilar. To those less
familar, basically the termination of cable screens to the internal 'nought
volts' instead of chassis.

An infuriating final hum/bzz was traced to a 'wall wart' powering some
equipment in one of the 'toy racks'. After that - pure silence. Out of 4
engineers, I was the only only one with the necessary acuity of hearing and
technical expertise to track it all down too. Not that I got much thanks for
it of course.


Graham