3 dB bandwidth

[Pooh Bear]

Indeed. I don't think TTS accounts for 3dB SPL being the minimum
detectable change under the test coditions above, though. Below
65 or 70 dBA SPL there is no TTS.

At that kind of SPL - I'm sure you're mainly right !

Try 90-100 and it gets interesting.

Graham

 

[Pooh Bear]

Sure, the ear brain is not very good at absolute measurements.

It's excellent at relative nevertheless.

I once performed a blind test to 'line up' a multitrack audio tape recorder by ear though -
lol !.

I managed to match the track one calibrated test tape playback levels to 0.3dB. This
potentially explains a lot of the golden ears stuff. You have to *educate* your ear to work
that well.

Graham

 

[Pooh Bear]

They all do. You are mistaken. A 3db change in volume is *easily*
detectable by anyone. A figure of 1db would be more relevant as a rough
guide to a "not always immediately detectable when drunk".

Actually, ( basically you're right ) 1dB is the volume change discernable
by the supposed 'average' listener in average situations.

A 'trained ear' has little trouble trebling that accuracy.


Graham

 

[Pooh Bear]

Even though I'm no expert, it seems feasible that 1 db would be
"just detectable"; 3 db is, after all, _twice_ as much power!

I've also heard or read somewhere that it takes a full 10 db change to
sound "twice as loud".

You're right and few ppl know it or understand it.

I guess few ppl care to imagine why we call them *deci* Bels.

Simple answer.

It's 1/10 th of a Bel ! A Bel being the ratio that sounds to the ear like a
doubling of intensity. Named after Alexander Graham Bell of telephony fame.

Graham

 

[Pooh Bear]

Depends what you mean by "modern". -0.5dB performance was trivially and
cheaply achievable 25 years ago.

In valve amps ? Erk !

Essentially you're right. Pro-audio has always tried to make the passband as
flat as possible. You won't find me arguing over that one for sure !

Graham

 

[Pooh Bear]

Yeeeeees! That's a 3dB drop.

No it isn't ! See Ohms Law !

Actually neither one of us should be saying "drop." If I had
specified power drop and you had specified voltage drop it
would have been clear that we are both right.


Try to make it work without transistors sometime.

You really mean transistors ?

I studied them when I was 12 !

In the days
when we all used vacuum tubes/valves and transformers, getting the
maximum amount of power out of one transformer and into the next
transformer was important, thus the matching, and thus the 3dB
power drop.

That's why toobs are only used by nitwits these days.........

< plonk >

Graham

 

[Pooh Bear]

In the days
when we all used vacuum tubes/valves and transformers, getting the
maximum amount of power out of one transformer and into the next
transformer was important, thus the matching, and thus the 3dB
power drop.

I forgot to mention. Not in audio. RF I expect.

You can voltage match toobs in audio perfectly well. I have done so myself.
I can design discrete vacuum tube, bipolar or fet ( junction or MOS )
circuitry and any amount of of IC circuitry inclusing DSP and its
micrcontroller host requirements..

I trust that explains !

Graham

 

[Kevin Aylward]

No it isn't ! See Ohms Law !



You really mean transistors ?

I studied them when I was 12 !


That's why toobs are only used by nitwits these days.........

Well it would certainly do by back a service by not being such a nitwit.
My Fender Twin Combo is just about impossible to carry single handed up
the stairs.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Kevin Aylward]

In valve amps ? Erk !

Essentially you're right. Pro-audio has always tried to make the
passband as flat as possible. You won't find me arguing over that one
for sure !

Dont forget the valve telephone SSB amps. Flat from 60Khz to 120Khz at
0.01% thd. They needed to be as they had 100s in a chain.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Kevin Aylward]

Yeeeeees! That's a 3dB drop.

Actually neither one of us should be saying "drop." If I had
specified power drop and you had specified voltage drop it
would have been clear that we are both right.


Try to make it work without transistors sometime. In the days
when we all used vacuum tubes/valves and transformers, getting the
maximum amount of power out of one transformer and into the next
transformer was important, thus the matching, and thus the 3dB
power drop.

You havent the slightest idea of what your talking about. You have
learnt a phrases from somewhere with no idea as to how and when they are
used.

The maximum power transfer theorem is useless and irrelevant for
many/most power amp situations.

Loads for most power amps, if not all are determined from the maximum
voltage and current ratings of the devices used. Period. For example, if
a tube has a max voltage of 400V and a max current of 100ma, it wants to
see a load of 4k, other wise one or the other aspect of the tube ratings
will be wasted, hence a bigger more expensive device is being used. This
is also true for RF power amplifiers. A transistor with an 15V max V
rating and 1A max current will want to see a load of 15 ohms. That's
what one does when one "matches".

Matched power means that one will waste 1/2 the power in the driving
source. This is about the daftest thing one can do for a power amp.

Hands up those that actually know when impedance matching actually has a
use?

Hint: "Singing" return loss on a 4 to 2 wire converter.
Hint: Switching fast signals.

{snip more drivel}


Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Pooh Bear]

Well it would certainly do by back a service by not being such a nitwit.
My Fender Twin Combo is just about impossible to carry single handed up
the stairs.

Sorry mate, they sound *great* on guitar !

I had the audiophool fraternity more in mind when I said that.

A bit of colouration / soft-compression and THD makes guitar sound wicked !
You pay the price in iron though.

Graham

 

[Guy Macon]

No it isn't ! See Ohms Law !

Sigh. Another ineducable newsgroup participant.

The formula for calculating power decibels is:

Po
G = 10 log10 ----
Pi

Where
G = Gain in dB
Po = Power output from the device
Pi = Power input to the device


The formula for calculating voltage decibels is:

Vo
G = 20 log10 ----
Vi

Where
G = Gain in dB
Vo = Voltage output from the device
Vi = Voltage input to the device


Or. if you don't believe me, you can read this tutorial:

[ http://home.comcast.net/~zcomco/decibel_1.htm ]

or this one:

[ http://et.nmsu.edu/~etti/fall96/communications/db/db.html ]

...nitwits...

You can join Aylward in my killfile. Assuming that he still posts to
sci.electronics.design, the two of you can have your own little flame
war without bothering me with the personal attacks that you think are
an acceptable alternative to having a civil discussion on the topic
at hand. Maybe later in life, after you have learned to read, write,
spell, and count, you will have more success. True, these are rudimentary
skills that many of us "normal" people take for granted that everyone
has an easy time of mastering. But we sometimes forget that there are
"challenged" persons in this world who find these things to be difficult.
If I had known that this was true in your case then I would have never
have exposed myself to what you wrote. It just wouldn't have been
"right." Sort of like parking in a handicap space. I wish you the
best of luck in the emotional, and social struggles that seem to be
placing such a demand on you.

*plonk*

 

[Don Bowey]

Well it would certainly do by back a service by not being such a nitwit.
My Fender Twin Combo is just about impossible to carry single handed up
the stairs.

So put 3 dB in each hand.

Don

 

[Pooh Bear]

Guy Macon wrote:

I note that you redirected my reply to alt.dev.null !

I think that speaks for itself ! You're a usenet troll and clearly know
nothing about electronics whatever.

Here's my original reply that you attempted to censor !


.............................................................................................................

The formula for calculating voltage decibels is:

Vo
G = 20 log10 ----
Vi

Where
G = Gain in dB
Vo = Voltage output from the device
Vi = Voltage input to the device

Yes.

So when Zin = Zload ; Vo/Vi = 0.5

Log10 ( 0.5 ) = -0.301.....

G = -6.02.....

Shame you didn't bother to check the math wasn't it ?

Killfile ? I'd be pleased to be in the killfile of someone who doesn't even
understand basic dB calcs !

Sorry to anyone else I have may offended. I loathe incompetence when it's
stuffed up your nose by a half-arse who erroneously and elaborately wants to
make a cheap point of correcting your supposed 'error' without even bothering
to check his own sums first !

Graham

 

[Pooh Bear]

Sigh. Another ineducable newsgroup participant.

Once again you misdirected my reply to
alt.dev.null.................................................

My reply is below

...............................................................................................................................

Don't waste my time on formulas I already know.

In audio 600 ohm working the source Z is 600 ohms and the load Z is also 600
ohms.

That forms a potential divider with a value of 0.5.

Thats -6dB !

Don't play semantics with your 10 log, 20 log stuff. I eat ppl like you for
breakfast ! After which I'm employed to sort out their ****-ups.

Graham

 

[Don Bowey]

Once again you misdirected my reply to
alt.dev.null.................................................

My reply is below

..............................................................................
................................................

Don't waste my time on formulas I already know.

In audio 600 ohm working the source Z is 600 ohms and the load Z is also 600
ohms.

That forms a potential divider with a value of 0.5.

Thats -6dB !

Don't play semantics with your 10 log, 20 log stuff. I eat ppl like you for
breakfast ! After which I'm employed to sort out their ****-ups.

Where do you obtain the 0.5 value and what is the "potential" divider?

When an amplifier's input and output impedances are the same (for example
600 Ohms), and it's gain is adjusted with a 600 Ohm 0 dBm input signal, to
provide a 0 dBm output into a 600 Ohm meter, There is neither gain nor loss.
Only an impedance mismatch or an uncalibrated oscillator or meter will
provide a different "view."

Don

 

[Kevin Aylward]

Where do you obtain the 0.5 value and what is the "potential" divider?

Ro/(Ro + Rl)...dah...

When an amplifier's input and output impedances are the same (for
example 600 Ohms), and it's gain is adjusted with a 600 Ohm 0 dBm
input signal, to provide a 0 dBm output into a 600 Ohm meter, There
is neither gain nor loss.

Sure, if you "adjust the gain", i.e. increase it. That is beside the
point.

The point is that given that one has an output from a *low* impedance
source (i.e *the* typical case) that has an output matching resister,
there will be a loss of 0.5 when there is that same valued resister
connected to ground at the tap point, when referenced to the raw low
impedance output.

People rarely design an amp with an inherent non resister resistance to
match some standard load impedance. However, Marshal do that on some of
their transistor guitar amps to simulate tube amp characteristics.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Kevin Aylward]

Sorry mate, they sound *great* on guitar !

I had the audiophool fraternity more in mind when I said that.

A bit of colouration / soft-compression and THD makes guitar sound
wicked ! You pay the price in iron though.

I did realise you were not referring to guitar amps graham.


Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Kevin Aylward]

It's excellent at relative nevertheless.

I once performed a blind test to 'line up' a multitrack audio tape
recorder by ear though - lol !.

I managed to match the track one calibrated test tape playback levels
to 0.3dB. This potentially explains a lot of the golden ears stuff.

Well, I will quible on "a lot".

You have to *educate* your ear to work that well.

Yes. The ear is quite sensitive under the right conditions, especially
when trained. There is no doubt that pretty much all non musical minded
individuals simply do not recognise what parts belong to what
instruments in a finished piece of music. Ask them if the bass is too
loud or soft, and they will have no idea. One has to learn to correlate
prior knowledge of expected sounds with new sounds.

I do find it quite fascinating how I can pick out the individual
intrument parts of music, and then sequence them. Most of the
information is in the same bandwidth at similar levels, so how does the
brain do it? Try and get a computer to do that and your nacked. It
clearly uses come sort of correlation technique, but the details are
still pretty amazing.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Robert Latest]

Thing is, if the power goes out I can keep going. A long time ago they
pestered me about it at a client's lab and one of the engineers bragged
about a new calculator with "continuous memory" that didn't fail when
the battery died. I told him my slide rule had continuous memory as
well.

My most-hated electronic calculator is also my best one. I bought
it about 15 years ago; it is programmable and whatnot.

Ten years ago, when I turned it on, it told me, in clean
black-on-white alphanumeric characters, that its battery was low
and I had to change it. Nothing else worked any more.

The way an electronic pocket calculator is supposed to work when
the battery goes out is to get progressively fainter until, after
at least a decade of usage, you have to squint at the LCD from a
certain angle to make out the numbers. Then you buy a new one.

Having lost interest in the fancy calculator, I quickly misplaced
and forgot all about it. Recently, I found it again at the bottom
of a junk drawer and turned on. "Battery low", still in full
contrast.

All my LCD calculators now have PV cells.

robert