Re: the are only two kinds of amplifiers


"Ruud Broens" <broensr@xxxxxxxxxx> wrote in message
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>
> <nyob123@xxxxxxxxxxxx> wrote in message
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> :
> : "Clyde Slick" <artsackman@xxxxxxxxxxx> wrote in message
> : news:YmMif.2109$Ue2.639@xxxxxxxxxxx
> : > It most certainly is an assumption.
> : > I heard differences you are neither able to hear nor to measure.
> : > Buy a hearing aid, or come up with some better ways to measure.
> : >
> : If they can't be measured they can't be heard either.
> :
> :
> Maybe so.

Until someone identifies some new thing there is nothing known that people
can hear that can't be measured. Things that can't be heard but are present
in an audio signal can also be measured. The measuring equipment is far
more sensitive than the ear.

However, the same problem that plagues abX is at hand here:

That people reject it out of hand?

> you can measure temperature, relative humidity, illumination level and
> what not, how are the results relevant to the question of difference ?

They aren't. There's either an audible differnence or not.

> Iow, to state that some measurements or metric are relevant do not
> make it so. Usually, not relevance, but convenience and available
> measurement equipment have set the standard and type of measurements :-)
>
> THD, for instance, is calculated with a summing of the squared levels of
> the various harmonic distortions - not at all a correct weighing of the
> actual
> perception of 'aggravation' by these distortion components - as is known
> for decades :(
>
> At a more fundamental level, the mental model of having some
> pristine signal and a separate 'distortion level treshold function' in the
> listener is just not the way perception works. So while at some
> instances,
> as little as 0.03 % distortion is clearly noticeable*, at other times,
> several
> percent will pass by unnoticed**.
>

AFAIK 1% is where it becomes noticable for humans.

> Under dynamic conditions, that is, with music, things like time domain and
> frequency domain masking take place. Many perception modifiers
> (i prefer that to the rather loaded-with-connotations-term bias) are at
> work,
> whether sighted, blinded, double or tripled, whatever ;-) listening is
> done,
> making it an individual experience that cannot readily be lumped together:
> that would make as much sense as saying that the average taste preference
> is "red herring with sour cream and strawberry ice on top".
>

It is still known that a DBT IS vastly more reliable for evaluating
differences than any form of sighted listening. There is ample data on this
and I've posted plenty of the titles and authors who have done the research.
As I said to Ludovic, a simple e-mail to Sean Olive will get you more
information than you need on the subject of blind evaluations vs. sighted
ones.

> Of course, distortion is just one aspect, frequency range, frequency
> response,
> noise, output impedance, horizontal and vertical dispersion vs. frequency,
> sensitivity, pulse response, compression, jitter are some other metrics
> that are
> applicable with some of the components in the audio reproduction chain.
>
No properly functioning CD player has audible jitter.
Dispersion is the province of loudspeakers as is pulse response.
SS amps present a much more speaker friendly impedance than do tubed amps.
There are some people that say there is no vertical dispersion, I'm not so
sure.
Certainly loudspeakers play the single most important role in what we hear.
There's not much we can do about the recordings and how much or how little
compression is used.

There is no audio gear tha I know of or at leasthat I would be interested in
that can't produce the entire audible frequency range.

> Your claim to know "what one is able to hear" is highly suspect.

It's not just me saying it. There is plenty of research that demonstrates
what is audible and what is not. No small amount of it comeing from
research into hearing aids.

> It would also render a lot of testing and evaluation in the real world
> rather
> pointless, as it could then be established from a simple set of
> measurements,
> some metric, fed into some weighing matrix and..presto audible or
> non-audible
> comes out -- i think NOT.
>

I suggest you read some of the research and then see what you think. In any
case the world of subjectivist audio is a far cry from the real world and
what audio components are actually capable of.

> Rudy
>
> * in a 1000 Hz sine wave, in a carefully set up university experiment, by
> some of
> the participants..others had trouble with anything under 0.5 % :-)
> ** playing back music, containing 30 - 60 Hz components at reasonably
> loud
> levels, all speakers will give you such distortion levels (except some
> megasized
> woofers:)

With loudspeakers the only way you can reduce distortion is with more
drivers covering the same frequency range, or new, better materials. 5% THD
is very typical, especially for woofers. We've grown used to that level of
distortion and there's not mich that we can use to compare that doesn't have
the same amount, but adding in 10% more from anything like the WAVAC woujld
certainly show up as audible

>
The standard for THD has been anything over 1% is audible. 10% as is the
case for the WAVAC is simply crap.


.

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