Wattage

[DarkMatter]

You are better off trying to get that from the manufacturer. It is a nebulous
figure anyway and lies are rampant. I assume you really want to know if your
amp will smoke it. Bear in mind the numbers for amps are also more marketing
than science.

Not if it is a reputable maker. Amp specs are true to form correct
from many reliable producers of home audio equipment.

 

[DarkMatter]

Wow! You're a big talker. However, you don't quote your
opponents, but berate them. ...perhaps to make you look somehow
superior? Please! Learn the rules of the Usenet and quote and
respond. If you can't take heat, leave the kitchen. The Usenet
isn't your mother's tea party.

Still trolling eh, Keith?

 

[[email protected]]

Cameron Dorrough wrote:

In my (brief) time doing concert audio, all we ever needed to do to measure
speaker characteristics was to hook them up to a Tektronix impedance
analyser, run the tests, print the graphs and hand them over to the cabinet
designers.

Well, that puts you one up (at least) on me. Never did concert
audio. With my tin ear, they wouldn't send out for a cello -
they'd send out for a Smith & Wesson to provide me with some
"negative feedback".

 

[Cameron Dorrough]

Well, that puts you one up (at least) on me. Never did concert
audio. With my tin ear, they wouldn't send out for a cello -
they'd send out for a Smith & Wesson to provide me with some
"negative feedback".

Coool! Concert audio is over-rated. Lots of lugging large crates
around and shuffling them into the right order - cables running everywhere -
lots of noise (from fussy musicians) - lots of standing for hours on end
eating free pizza and drinking litres of free Coke - early mornings,
followed by the next early morning.

Don't get me wrong, it is *very* satisfying to get a good mix, with the
mid-highs tuned just right and the reverb bouncing off the walls (and to see
the punters thoroughly enjoying themselves)..

Audiophool stuff it's not (more like drown out the echoes!)... but these
days I value my sleep (and my ears).

Cameron

 

[[email protected]]

No, I *meant* the "OUTPUT IMPEDANCE OF MOST AUDIO CIRCUITS IS
NIL". Not any variation in impedance.

Most audio circuits these days are emitter-follower sorts of
things, and as such have damned near zero output impedance.

Uhhhh... sorry, I don't understand that. An emitter follower
with no emitter resistor?

 

[Cameron Dorrough]

<snip>

Perhaps you don't understand the terms you're slinging around?

Maybe I don't - but then I'm no Electronics "expert".. OTOH, a quick Google
search on "output impedance" reveals that a host of highly-respected
technology companies including Tektronix and Belden don't either.

eg. http://www.tek.com/site/ps/0,,21-07055-SPECS_EN,00.html

Perhaps you know something they don't??

Cameron

 

[[email protected]]

Sure. Why is an emitter resistor needed?

Are you talking about an emitter follower with emitter
connection only to the speaker? If so, the speaker load
is an essential part of the output circuit. In that case,
the output impedance is essentially the impedance of the
speaker - which is NOT nil.

So, what are you thinking of? What is the emitter
circuit you envision?

 

[[email protected]]

If you insist, though I would add it's complement to get four-
quadrant operation.


Nope. The output impedance of such an amplifier is nil and has
"nothing" to do with the load.

It's a voltage source.

That helps. An ideal voltage source would have 0 internal
impedance.

Exactly as you describe, with the addition of the complement so
we can do more than one quadrant supply.

You apparently have no understanding of what "output impedance"
is.

Very likely - certainly less understanding than I would like
to have. That's why I ask questions.

Hint: It's not the impedance seen at the output. It
describes the characteristics of the output (not the load), and
in this case is more-or-less the output transistor's base drive
(also a low impedance) divided by the beta of the output
transistor. ...a rather low number, I.e. nil.

So if I'm understanding you right, output impedance is a model
representation of how the output behaves, and is not related
to circuit impedance which is a real, measurable thing. Do I
have that right?

 

[[email protected]]

Asking questions from ignorance is laudable. Making statements
from ignorance isn't.

Assuming ignorance is a mistake. Both questions and statements
can come from an effort to understand what the other guy is
saying, and have nothing to do with ignorance.

Only half right. The output impedance of a circuit is easily
measurable. Take the audio amp you propose, draw another amp out
of it, if the output voltage drops one volt, the output impedance
is one ohm (scale as appropriate). Input and output impedances
are "small signal" quantities, so one must be careful to apply
them appropriately. They *are* real though.

So if I understand you, output impedance Zo = (Ve-Ve2)/(I2-I)
with Ve measured with respect to ground. And, to get back
to what started this off, Zo does not change with frequency
between ~20 to ~20,000 Hz. Do I properly understand what
you are saying?

 

[DarkMatter]

Assuming ignorance is a mistake. Both questions and statements
can come from an effort to understand what the other guy is
saying, and have nothing to do with ignorance.

Keith likes to point inappropriate fingers of falsehood. He does it
at every turn. Expect more.

 

[[email protected]]

You were clearly ignorant of what (output or any other) impedance
means, yet jumped on my case when I called you on it. You
didn't' ask, you attemptedd to tell. Sorry, but you were
*wrong*.

You are mistaken. It was Cameron who jumped on your case,
not I. I NEVER jumped on your case. If anything I have
posted in this thread or any other is mistaken for me jumping
on you, I apologize.

I'm sorry to have bothered you.