"Stewart Pinkerton" wrote in message
...
I'm not surprised that a slider jockey would be unaware that the term
'power bandwidth' implies -3dB, but never mind.




Yes I was quite aware of that, but I wondered about your use of
the term "frequency response at full power" The correct
definition of power band width is in fact +/- 3dB.

"Slider jockey" is not really an appropriate evaluation of what
I do. I suppose we must put it down to your lack of familiarity with
what actually goes on in the recording process:-))

You have used the term fader-twiddler somewhere else,
I believe. This too is inaccurate, as faders move N-S and so cannot
be "twiddled" One could I suppose twiddle a digital rotary encoder.
I work with those quite often:-))

But why do you always have to be so personal and insulting?
It does not stimulate interesting communication, and more
importantly, you are keeping people away from this group
who would otherwise be pleased to take part.
Perhaps this is your intention?

(snip)

Presumably you are referring to the limitations of the output
transformer.

Generally, that does indeed set the limit, especially at the low end.
A full-power bandwidth of 20-20kHz +/- 1dB implies a -3dB
'power bandwidth' of 10-40kHz. The low end is always a weakness with
valves.

I have mentioned this in a separate post.


Cordially,


Iain

In article , Stewart Pinkerton
wrote:
On Sun, 31 Oct 2004 19:40:33 +0000, Chris Morriss
wrote:


V2000 technically should have been head and shoulders above the rest,
but they were perhaps too sophisticated to be reliable in the rough and
tumble of everyday use.

I've never quite understood this. Why do distribution media for use in
a stable domestic environment have to withstand 'rough and tumble'?

Well, I also had a V2000 for some years and was quite happy with it.
However after a while it began to misbehave. Turned out to be due to the
mechanical assembly slowly warping by minute amounts and putting the system
out of alignment. Someone else I knew had a similar experience. My
impression is that the recorders were vulnerable to this kind of thing.

Above said, it lasted over 10 years, so hardly a serious
design/manufacturing problem for a standard consumer item. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Iain M Churches
wrote:

"Jim Lesurf" wrote in message
...

Some 'reviews' go further, but many do not. Others now simply call
themselves 'auditions' and use this as a way of washing their hands of
doing any measurements that might tell anyone other than the writer
concerned anything that might help them decide if the amp (or
speakers) might be suitable for anyone other than the person writing
the 'audition'.

But doesn't a proper technical evaluation add increased credibility to a
review?

I would say "yes". However with the proviso that the reviewer has to do
relevant tests, and then both understand and explain them reliably and
clearly.

and the outlay for such a test is not large. I wonder if there are some
politics also involved here?

Can only speculate. In part I think it is simply cheaper, quicker, and
easier, to employ reviewers who don't bother much with measurements. Bear
in mind that 20-odd years ago we reached a situation where the kit costs
and measurement costs exceeded the amount a magazine would pay. The
reviewers then also became 'consultants' sic to manufacturers. They would
charge makers to 'test and comment on' a unit before it was released. This
was an extra source of income.

However for many years they then did this without mentioning in reviews
that they'd already tested the item (or its competitors).

The risks are fairly obvious. e.g. Makers started to feel that they *had*
to get such a consultancy check as it would improve your chances of a
decent review.

Another problem, I'm afraid, is that some reviewers have little or no real
understanding of the relevant engineering or science. Thus it is now
routine in audio mags to read statements that are either incorrect in fact,
or contradict may be formally proven and is in the relevant textbooks.

e.g. a review a while ago that stated what kind of CD mechanism a player
had, and how it worked. Since the discription did not fit what I though I
knew, I asked the designer (who I happened to know). He confirmed that what
was in the review was simply wrong, but that there was no point in trying
to get it corrected. They liked the player, so sleeping dogs... :-)

Another problem is that - from what I understand - editors tend to feel
that 'technical' info may put off some readers. The assumption is that
readers don't want to know about bits or impedances, just be told 'A sounds
like it has more bass than B'. Hence we have subjective reviews that tell
you what the reviewer thought, using their room, their taste in music, etc,
but no real info on what anyone else might think.


I have noticed that some amplifier manufacturers like to demonstrate
their amplifier with a particular speaker.

Particular combinations may be optimal for various reasons. Other may
sometimes lead to failures as well as poorer results!

That would be the reason. I am sure also, that the buyer would like to
audition a new amplifier with his own speakers in his own room, or a new
pair of speakers with his own amplifier in his own room. So hifi demo
rooms do not tell the whole story.

Very much so. Alas, the area of speakers and room acoustics tends to not
get the attention it deserves as it hasn't been an opportunity for people
to sell boxes via magazine ads and reviews. :-)


I wonder why high end amplifier manufacturers do not work more closely
with high end loudspeaker manufacturers, to produce a more homogenous
combination. Or maybe they do?

In some cases, yes. However bear in mind that designing and making a *good*
loudspeaker is very very hard. Hence the LS designer is happy to shovel
some problems onto the amp designer. Despite my moans about the poor old
amp designer, I'd say that designing an amp was much easier than designing
a speaker. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Iain M Churches
wrote:

"Stewart Pinkerton" wrote in message
...
Okeley Dokeley. Quote me one valve amplifier from any manufacturer,
which is specified at 15 Hz to 50kHz, even to 1dB *at full power*. Not
a problem for any decent SS amp, but unheard of with valves.

I can't do that. But what I can do is to mention the C30/50 50W
amplifier which I have in my own music room. This was a shared project
between myself and a design engineer at Sverige Radio, and has the
following spec.

FR (+/- 1dB at 1W) 10Hz to 80kHz Power Bandwidth (+/- 3dB with 0.1%
THD) 15Hz to 70kHz

This amp has a formal test certificate, and six of them have been built
in the past three years or so.

I assume the above is with a resistive load of appropriate value.

I'd be interested to know the output impedance across the same bandwidths.
Also what maximum current the amp will deliver at various frequencies, and
how the THD varies into various difficult loads.

The problem is that - valve or SS - it is much easier to build an amp that
works nicely into 8 Ohm loads with sinewaves than it is to ensure the same
sort of perfomance into 'difficult' speakers with real music.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

On Sun, 31 Oct 2004 23:43:52 +0000 (UTC), Stewart Pinkerton
wrote:


Elcaset was indeed technically excellent when compared with
Musicassette. However, Betamax was *not* the best of the available VCR
technologies. I still have a Philips Video 2000 recorder...... :-)

When they were good they were very, very good, but when they were bad
...(etc).

V2000 technically should have been head and shoulders above the rest,
but they were perhaps too sophisticated to be reliable in the rough and
tumble of everyday use.

I've never quite understood this. Why do distribution media for use
in a stable domestic environment have to withstand 'rough and tumble'?

You're domestic environment must differ from that of a large section
of the population, but I think that the main problems of the Philips
machines was the manufacture. They produced many brilliant designs at
the time, but they didn't seem able to make them reliable.

Bill

On Mon, 1 Nov 2004 09:50:14 +0200, "Iain M Churches"
wrote:

Some 'reviews' go further, but many do not. Others now simply call
themselves 'auditions' and use this as a way of washing their hands of
doing any measurements that might tell anyone other than the writer
concerned anything that might help them decide if the amp (or speakers)
might be suitable for anyone other than the person writing the 'audition'.

But doesn't a proper technical evaluation add increased credibility to
a review? and the outlay for such a test is not large. I wonder if there
are some politics also involved here?

As far as I can see the main factor is money. To conduct good tests
needs someone with access to good test equipment, the ability to use
it and preferably who understands what they are doing. This is
expensive. It costs very little to merely express an opinion.

Also the publishers will have done their market research and will
realise that almost none of their readership either read or understand
technical assessments, so comissioning and publishing them involves
spending money for no return.


Alternatively, if the designers of a specific amp go out of their way to
point out their design is good in these areas, it may be tested for them.
But then there will be no real comparison results for many competing
designs...

I wonder why high end amplifier manufacturers do not work more closely
with high end loudspeaker manufacturers, to produce a more homogenous
combination. Or maybe they do?


The forward thinking manufacturers cut out interface problems
altogether by using active speakers. One amp for each driver with
electronic crossovers; reduces amp/driver interface problems,
simplifies crossover design and it should reduce costs. (Decent
analogue crossover components are expensive).

This is now very common in the semi-professional area, and has been
common in the professional arena for many years.

Meridian is the leading advocate of this approach in the field of
Hi-fi.

Bill

On Mon, 1 Nov 2004 09:57:57 +0200, "Iain M Churches"
wrote:

"Stewart Pinkerton" wrote in message
.. .
I'm not surprised that a slider jockey would be unaware that the term
'power bandwidth' implies -3dB, but never mind.

But why do you always have to be so personal and insulting?

Because you keep referring to 'the print room'. What matters is the
*content* of posts, not the background of the author.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
On Mon, 1 Nov 2004 09:57:57 +0200, "Iain M Churches"
wrote:

"Stewart Pinkerton" wrote in message
. ..
I'm not surprised that a slider jockey would be unaware that the term
'power bandwidth' implies -3dB, but never mind.

But why do you always have to be so personal and insulting?

Because you keep referring to 'the print room'. What matters is the
*content* of posts, not the background of the author.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Surely both the content and the authors background lends credence to the
validity of those posts. If I was consulting a doctor I would like to be
assured that he/she holds valid qualifications for his/her position and has
practiced successfully within his/her field for a suitable period - (far too
easy to bury your mistakes Mr Shipman)!!!
I certainly would not take the word of someone working not from a doctors
surgery who purports to be a doctor but shows neither the certified
documentary evidence or concrete proof of a solid working experience within
the field in question. I have seen Iain's name on many IMO good recordings
and I quickly recalled his name when he started posting, his further
postings and e-mails certainly satisfied me of his credentials.

Mike

In article ,
wrote:
On Mon, 1 Nov 2004 09:50:14 +0200, "Iain M Churches"
wrote:

But doesn't a proper technical evaluation add increased credibility to
a review? and the outlay for such a test is not large. I wonder if
there are some politics also involved here?

As far as I can see the main factor is money. To conduct good tests
needs someone with access to good test equipment, the ability to use it
and preferably who understands what they are doing. This is expensive.
It costs very little to merely express an opinion.

I am inclined to agree. Although the 'nice thing' about being a reviewer is
that you can dismiss years of some-one else's hard work and experience in a
few mins, based upon little more than such 'opinions'.

Also the publishers will have done their market research and will
realise that almost none of their readership either read or understand
technical assessments, so comissioning and publishing them involves
spending money for no return.

To take that slightly further. I have had comments from people associated
with magazines that they feel that some/many readers *dislike* being
presented with too much 'technical' information as they find it annoying
that they don't understand it. Bit like the comment attributed to Hawking
and his editors that each equation in a book halves the number of sales.

Whether the above view is reliable or not, the problem is that some editors
and writers behave as if they assume it to be the case. :-/


The forward thinking manufacturers cut out interface problems altogether
by using active speakers. One amp for each driver with electronic
crossovers; reduces amp/driver interface problems, simplifies crossover
design and it should reduce costs. (Decent analogue crossover components
are expensive).

This is now very common in the semi-professional area, and has been
common in the professional arena for many years.

Meridian is the leading advocate of this approach in the field of Hi-fi.

Yes. My regret is that they don't make Electrostatics. ;-)

Fortunately, the newer speakers like the 988's and 989's are much easier to
drive than old 57's... :-))

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Mike Gilmour" wrote


crap snipped


Surely both the content and the authors background lends credence to the
validity of those posts. If I was consulting a doctor I would like to be
assured that he/she holds valid qualifications for his/her position and
has practiced successfully within his/her field for a suitable period -
(far too easy to bury your mistakes Mr Shipman)!!!
I certainly would not take the word of someone working not from a doctors
surgery who purports to be a doctor but shows neither the certified
documentary evidence or concrete proof of a solid working experience
within the field in question. I have seen Iain's name on many IMO good
recordings and I quickly recalled his name when he started posting, his
further postings and e-mails certainly satisfied me of his credentials.



A good point perfectly made, IMO.....