New webpage on loudspeaker cables
 

On Thu, 08 Oct 2009 13:38:08 +0100, Jim Lesurf wrote:

In article , John
wrote:
On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:



Jim Lesurf wrote:

Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a
few months ago.

What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on
the listening experience.

I wouldn't want to buy an audio amp that could potentially do anything
at 30mHz. It's madness.

Then you may have a problem to worry about. :-) Many of the gain devices
in audio power (and pre) amps have gain at frequencies reaching up into
that region. As a result *unless* the designer/maker has ensured
unconditional stability and no other problems affected by RF loading, then
changing the cables can affect the amplifier behaviour.

Yeah but bandwith can be tailored. Medical instrumentation amplifiers are
an example where attention is closely paid to when designing
equipment. You can fix the bandwith in any audio amplifier, you can even
have software filters with monstrously steep drop offs/skirts for digital
equipment. If an audio amplifier is comprised of a number of carefully
designed stages no single stage having a very large gain and designed
with a roll off beginning at about 25kHz then I don't see why any
appreciable rf currents should come into it.


If you wish to avoid the 'madness' then you have two choices...

1) never buy or use any audio amplifiers.

No, it is possible to use an audio amplifier which will not appreciably
boost rf signals.

or

2) only buy ones where the maker/sellers/reviewers have told you the
unit is unconditionally stable and that behaviour is unaffected by RF
loading.

I noticed in the 70's how the fashion for extended frequency response in
audio amplifiers was creeping up and up to 200kHz and more and am not
surprised that the uneducated now think higher is better and who now may
be wowed by amps with a high gain response up to 30 mHz or more. It's a
foolish and pointless pursuit.


Otherwise you have just 'plug and prey' to go by. :-)

Ideally you want the gain to tail off at just above normal human hearing
~ 20kHz. It's not well known but ultrasonic sound at high intensity is
capable of causing tinnitus (I'm talking power levels found in
ultrasonic burglar alarm systems which I have repaired and found out
from personal experience).

The problem, alas, is that the amplifier is still connected to the load,
via the cables, at higher frequencies. The gain devices will have gain at
these frequencies. And the length and type of cable will affect the load
presented to the amp at RF. Change the length or type of cable, and the
load seen by the amp will change. So if the system isn't unconditionally
stable then it may misbehave without you explicitly trying to put into it
frequencies above 20kHz.

Yes but I suspect you are talking about exceedingly poorly designed
circuits.


Chances are, anyone who has spent long designing audio amplifiers will
have seen them oscillate or otherwise misbehave at such frequencies with
some loadings. And that can then affect the audio behaviour. I've
certainly witnessed this. I have also seen someone puzzled by an amp
having high levels of distortion *at audio frequencies* that appeared with
some speakers but not others. Only to find later that using an
oscilloscope with wider bandwidth showed that the amp was producing bursts
of oscillations in the region well above 1MHz with one load, but not
another. He could not see the oscillations with the first scope he used,
so was baffled by the behaviour. The better scope showed the reasons and
helped him fix the problem.

I have also seen this with a real-world commercial amplifier that had a
high reputation and sold at a fancy price. So if the designer/maker don't
understand this and take care, it can get out into the home.

I have used and tested premium op-amps when designing
instrumentation for medical research and didn't have any difficulty with
rf springing up anywhere along the line. A single high gain block of
course is asking for trouble. You get what you pay for.


Slainte,

Jim

New webpage on loudspeaker cables
 

On Thu, 08 Oct 2009 11:19:12 +0100, John wrote:

Ahem, this debate seems to have been going on for more years than I care
to remember. To me, the main reason why some cables do sound different is
bad design of output stages themselves. After all, speakers are very weird
loads and if an amp is going to sound different just due to cables then it
does not bode well for how it will drive real speakers.

I'd say there is some truth in what you say but alas I have never come
across a situation where the substitution with bell wire of much heavier
multi-strand in the speaker leads where I can hear any difference between
the two and I have used some of the crappiest audio amps.


That's the only time I ever HAVE heard a difference, when competent
cable was substituted with an excessive length of bell wire. The
music got a little quieter.
See: www.auym23.dsl.pipex.com/cables.html

New webpage on loudspeaker cables
 

In article , John
wrote:
On Thu, 08 Oct 2009 13:38:08 +0100, Jim Lesurf wrote:


Then you may have a problem to worry about. :-) Many of the gain
devices in audio power (and pre) amps have gain at frequencies
reaching up into that region. As a result *unless* the designer/maker
has ensured unconditional stability and no other problems affected by
RF loading, then changing the cables can affect the amplifier
behaviour.

Yeah but bandwith can be tailored.

Indeed. Alas you may be confusing theory with reality, and presuming that
all items of equipment *are* ideally well designed. :-) You are also
perhaps confusing two other things. cf below.

Medical instrumentation amplifiers are an example where attention is
closely paid to when designing equipment. You can fix the bandwith in
any audio amplifier, you can even have software filters with monstrously
steep drop offs/skirts for digital equipment. If an audio amplifier is
comprised of a number of carefully designed stages no single stage
having a very large gain and designed with a roll off beginning at about
25kHz then I don't see why any appreciable rf currents should come into
it.

I appreciate that you may not see why. :-) I fear that may also be the
case for some designers and makers. Ideally, it won't. But the snag is that
reality may not accord with your (or their) presumptions. As I have
personally witnessed in reality on more than one occasion over the years.

Yes, you can design and build amplifiers that are unconditionally stable
and whose audio performance isn't noticably affected by ultrasonic/RF
loading.

And, yes, there are real amplifiers for which the above simply isn't true.
They can and do oscillate, and this can and does affect performance with
audio signals. They can also exhibit behaviours like distortion levels that
vary with RF loading. No need for you to deliberately inject RF for this to
occur. This is a matter of having observed the measured results.


If you wish to avoid the 'madness' then you have two choices...

1) never buy or use any audio amplifiers.

No, it is possible to use an audio amplifier which will not appreciably
boost rf signals.

Yes, it is indeed possible. But the universe does not guarantee that every
design you might use *will* accord with this possibility.

It is possible to take home a box of 6 brown eggs. But that does not
guarantee that *all* boxes of eggs only contain brown ones *when the box
does not tell you they are all brown*. Indeed, even some which claim to
contain brown eggs may not be correctly labelled. The snag here is that
many audio amplifiers don't tell you if they meet the criterion of being
uncoditionally stable or not.


or

2) only buy ones where the maker/sellers/reviewers have told you the
unit is unconditionally stable and that behaviour is unaffected by RF
loading.

I noticed in the 70's how the fashion for extended frequency response in
audio amplifiers was creeping up and up to 200kHz and more and am not
surprised that the uneducated now think higher is better and who now may
be wowed by amps with a high gain response up to 30 mHz or more. It's a
foolish and pointless pursuit.

I am afraid you are confusing having extended gain response of the overall
design with the design being able to oscillate due to poor design and
loading. The two things are not the same. Indeed, tailoring the intended
frequency response - if done poorly - can *increase* the chance of
instability problems. Or just move the frequency of oscillation.

So having a presented audio response that rolls away from about 20 kHz does
not guarantee the amplifier can't misbehave at much higher frequencies into
some loads. The presented response into the rated load does not tell you
about this, I'm afraid.

[snip]

Yes but I suspect you are talking about exceedingly poorly designed
circuits.

Yes, I am. The snag is that they do exist, and have been sold to the
public. I have seen them in the past, and the responses I have had to my
measurements do strengthen my concern that we can't be sure that all modern
designs are immune to the same basic physics involved.

The problem here is that makers and reviewers have largely stopped even
mentioning if a model/design is unconditionally stable or not. So to tell
we would now have to measure the presented gain *and* output impedance *of
every design being sold* over the region where the gain of the unit is
above unity, and measure its complex output impedance across that entire
range, then check if there is any load R+jI (where R= and I can be in the
range from + to minus infinity) that would satisfy the Barkhausen
criterion. if you find a solution the amp is not unconditionally stable.

Also note that 'gain above unity' for a power amp does not just mean
voltage gain. It may mean power gain, which can be a very different matter.

Even that isn't enough to rule out problems like an alteration in
distortion performance short of oscillation.


I have used and tested premium op-amps when designing instrumentation
for medical research and didn't have any difficulty with rf springing up
anywhere along the line. A single high gain block of course is asking
for trouble.

I have spent some years designing and testing audio amplifiers -
commercially, for research, and for personal use. Plus various other uses
of analog amps, signal conditioning, etc, for research and measurement. So
my comments are based on practical experience.

The problem here is partly that domestic hifi amps have to deliver high
powers into undefined loads. The designer has no real idea what the user
will connect to the amplifier - particulary at RF. Thus this situation
isn't like the much better defined one with lab instrumentation. When I've
designed kit for lab use, etc, I could define what the loading and
conditions of use would be. That makes establishing what is OK vastly
easier. You can't do that with domestic audio power amps beyond a vague
range of magnitude. And how many speaker designs have you seen complex
impedance plots for that extend much above 20kHz? Remember that we may
need to know to well above 1MHz in this case.

You get what you pay for.

Always? I'd say you 'pay for what you get' may be more common than 'you get
what you pay for'. :-) Paying a lot of money may sometimes be buying a
fancy designer label and a kewl look to impress the mates. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

New webpage on loudspeaker cables
 

On Thu, 08 Oct 2009 15:22:33 +0100, Laurence Payne wrote:

On Thu, 08 Oct 2009 11:19:12 +0100, John wrote:

Ahem, this debate seems to have been going on for more years than I
care to remember. To me, the main reason why some cables do sound
different is bad design of output stages themselves. After all,
speakers are very weird loads and if an amp is going to sound different
just due to cables then it does not bode well for how it will drive
real speakers.

I'd say there is some truth in what you say but alas I have never come
across a situation where the substitution with bell wire of much heavier
multi-strand in the speaker leads where I can hear any difference between
the two and I have used some of the crappiest audio amps.


That's the only time I ever HAVE heard a difference, when competent cable
was substituted with an excessive length of bell wire. The music got a
little quieter.
See: www.auym23.dsl.pipex.com/cables.html

Excessive length could mean a long run. I didn't do any long/short
comparison.

New webpage on loudspeaker cables
 

In article , John
wrote:
On Thu, 08 Oct 2009 15:22:33 +0100, Laurence Payne wrote:

On Thu, 08 Oct 2009 11:19:12 +0100, John wrote:

Ahem, this debate seems to have been going on for more years than I
care to remember. To me, the main reason why some cables do sound
different is bad design of output stages themselves. After all,
speakers are very weird loads and if an amp is going to sound
different just due to cables then it does not bode well for how it
will drive real speakers.

I'd say there is some truth in what you say but alas I have never come
across a situation where the substitution with bell wire of much
heavier multi-strand in the speaker leads where I can hear any
difference between the two and I have used some of the crappiest audio
amps.


That's the only time I ever HAVE heard a difference, when competent
cable was substituted with an excessive length of bell wire. The
music got a little quieter. See: www.auym23.dsl.pipex.com/cables.html

Excessive length could mean a long run. I didn't do any long/short
comparison.

Perhas also worth adding that how 'crappy' the amp is may not be the issue
when considering runs so long that the series resistance+inductance becomes
high. What might then matter is the impedance variations with frequency of
the loudspeakers chosen.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

New webpage on loudspeaker cables
 

On Thu, 08 Oct 2009 16:18:42 +0100, Jim Lesurf wrote:

In article , John
wrote:
On Thu, 08 Oct 2009 15:22:33 +0100, Laurence Payne wrote:

On Thu, 08 Oct 2009 11:19:12 +0100, John wrote:

Ahem, this debate seems to have been going on for more years than I
care to remember. To me, the main reason why some cables do sound
different is bad design of output stages themselves. After all,
speakers are very weird loads and if an amp is going to sound
different just due to cables then it does not bode well for how it
will drive real speakers.

I'd say there is some truth in what you say but alas I have never come
across a situation where the substitution with bell wire of much
heavier multi-strand in the speaker leads where I can hear any
difference between the two and I have used some of the crappiest audio
amps.


That's the only time I ever HAVE heard a difference, when competent
cable was substituted with an excessive length of bell wire. The
music got a little quieter. See: www.auym23.dsl.pipex.com/cables.html

Excessive length could mean a long run. I didn't do any long/short
comparison.

Perhas also worth adding that how 'crappy' the amp is may not be the issue
when considering runs so long that the series resistance+inductance
becomes high. What might then matter is the impedance variations with
frequency of the loudspeakers chosen.

It's my understanding - please tell me if I'm wrong - that the cab type
and size can affect the frequency/impedance response too. It's many years
since I built any cabs. The last ones were some transmission line designs
(kapellmeister) by Vivian Capel - details in some Babani publication I
don't have anymore. Fascinating book.



Slainte,

Jim

New webpage on loudspeaker cables
 

On Thu, 08 Oct 2009 15:33:16 +0100, Jim Lesurf wrote:

snip

Yes, you can design and build amplifiers that are unconditionally stable
and whose audio performance isn't noticably affected by ultrasonic/RF
loading.

And, yes, there are real amplifiers for which the above simply isn't true.
They can and do oscillate, and this can and does affect performance with
audio signals. They can also exhibit behaviours like distortion levels
that vary with RF loading. No need for you to deliberately inject RF for
this to occur. This is a matter of having observed the measured results.


If you wish to avoid the 'madness' then you have two choices...

1) never buy or use any audio amplifiers.

No, it is possible to use an audio amplifier which will not appreciably
boost rf signals.

Yes, it is indeed possible. But the universe does not guarantee that every
design you might use *will* accord with this possibility.

It is possible to take home a box of 6 brown eggs. But that does not
guarantee that *all* boxes of eggs only contain brown ones *when the box
does not tell you they are all brown*. Indeed, even some which claim to
contain brown eggs may not be correctly labelled. The snag here is that
many audio amplifiers don't tell you if they meet the criterion of being
uncoditionally stable or not.


or

2) only buy ones where the maker/sellers/reviewers have told you the
unit is unconditionally stable and that behaviour is unaffected by RF
loading.

I noticed in the 70's how the fashion for extended frequency response in
audio amplifiers was creeping up and up to 200kHz and more and am not
surprised that the uneducated now think higher is better and who now may
be wowed by amps with a high gain response up to 30 mHz or more. It's a
foolish and pointless pursuit.

I am afraid you are confusing having extended gain response of the overall
design with the design being able to oscillate due to poor design and
loading.

I am aware of things like parasitic oscillations which depending on the
circuit could take place in the leg of a transistor before any low pass
filtering in a later stage for example.

The two things are not the same. Indeed, tailoring the intended
frequency response - if done poorly - can *increase* the chance of
instability problems. Or just move the frequency of oscillation.

So having a presented audio response that rolls away from about 20 kHz
does not guarantee the amplifier can't misbehave at much higher
frequencies into some loads. The presented response into the rated load
does not tell you about this, I'm afraid.

Yes, I can see that.

[snip]

Yes but I suspect you are talking about exceedingly poorly designed
circuits.

Yes, I am. The snag is that they do exist, and have been sold to the
public. I have seen them in the past, and the responses I have had to my
measurements do strengthen my concern that we can't be sure that all
modern designs are immune to the same basic physics involved.

The problem here is that makers and reviewers have largely stopped even
mentioning if a model/design is unconditionally stable or not. So to tell
we would now have to measure the presented gain *and* output impedance *of
every design being sold* over the region where the gain of the unit is
above unity, and measure its complex output impedance across that entire
range, then check if there is any load R+jI (where R= and I can be in the
range from + to minus infinity) that would satisfy the Barkhausen
criterion. if you find a solution the amp is not unconditionally stable.

Also note that 'gain above unity' for a power amp does not just mean
voltage gain. It may mean power gain, which can be a very different
matter.

Even that isn't enough to rule out problems like an alteration in
distortion performance short of oscillation.

Well put.
I have never considered any of my hi fi gear to be anything more than what
it was designed to be. Certainly not perfection. In fact In this sphere I
am satisfied with much less than perfection. I wouldn't dream of or
imagine that I could run some hi fi in any circumstances. It's common
knowledge that they are multivariate systems with many parameters
which change and are inter dependant.

I have used and tested premium op-amps when designing instrumentation
for medical research and didn't have any difficulty with rf springing up
anywhere along the line. A single high gain block of course is asking
for trouble.

I have spent some years designing and testing audio amplifiers -
commercially, for research, and for personal use. Plus various other uses
of analog amps, signal conditioning, etc, for research and measurement. So
my comments are based on practical experience.

The problem here is partly that domestic hifi amps have to deliver high
powers into undefined loads. The designer has no real idea what the user
will connect to the amplifier - particulary at RF.

Again the audio amplifier should not pass any rf and if it did and it blew
up then the consumer has every right to compensation (my opinion). And as
for defined loads he should know what is likely to be presented to his
amplifier or for what loads he is designing/selling his amplifier? It's a
cop out to say I'm making an amp but I cant say what you can do with it.
It's a total waste. I think you will know the first rule of purchasing
computers, - know what you want it for then get one that will do the job.
That was the number one maxim before the pc became mainstream.

Thus this situation
isn't like the much better defined one with lab instrumentation. When I've
designed kit for lab use, etc, I could define what the loading and
conditions of use would be. That makes establishing what is OK vastly
easier. You can't do that with domestic audio power amps beyond a vague
range of magnitude. And how many speaker designs have you seen complex
impedance plots for that extend much above 20kHz? Remember that we may
need to know to well above 1MHz in this case.

You get what you pay for.

Always? I'd say you 'pay for what you get' may be more common than 'you
get what you pay for'. :-) Paying a lot of money may sometimes be buying
a fancy designer label and a kewl look to impress the mates. :-)

I'm always moaning to my wife after a shopping trip how most things are
not properly designed.

Slainte,

Jim

New webpage on loudspeaker cables
 

In article , John
wrote:
On Thu, 08 Oct 2009 16:18:42 +0100, Jim Lesurf wrote:

In article , John
wrote:


Excessive length could mean a long run. I didn't do any long/short
comparison.

Perhas also worth adding that how 'crappy' the amp is may not be the
issue when considering runs so long that the series
resistance+inductance becomes high. What might then matter is the
impedance variations with frequency of the loudspeakers chosen.

It's my understanding - please tell me if I'm wrong - that the cab type
and size can affect the frequency/impedance response too. It's many
years since I built any cabs.

Yes, it can. Part of the impedance properties of the LS unit stem from the
physical movement of the coil in the magnetic field field, altering the
'back EMF'. Changing the cabinet or its contents can alter the amount of
movement caused by a given applied audio signal, and this then changes the
current demanded. So the observed impedance changes.

However in most cases this is only likely to be obvious at low frequencies.
At high frequencies the movement for traditional 'cone and box' speakers
tends to become dominated by the mass of the driver. But it explains why
the impedance of reflex or ported or transmission line designs at LF tend
to differ from infinite baffle types. Typically with a single LF resonance
in impedance being converted into a pair. Bit like over-coupling a pair of
tuned circuits.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

New webpage on loudspeaker cables
 

In article , John
wrote:
On Thu, 08 Oct 2009 15:33:16 +0100, Jim Lesurf wrote:


I am afraid you are confusing having extended gain response of the
overall design with the design being able to oscillate due to poor
design and loading.

I am aware of things like parasitic oscillations which depending on the
circuit could take place in the leg of a transistor before any low pass
filtering in a later stage for example.

Yes. One of the problems here is that at RF a complex power amp may
resemble the Shackleton aircraft. A set of RF sensitive components flying
in close formation. :-)

[snip discussing causes]


Even that isn't enough to rule out problems like an alteration in
distortion performance short of oscillation.

Well put. I have never considered any of my hi fi gear to be anything
more than what it was designed to be. Certainly not perfection. In fact
In this sphere I am satisfied with much less than perfection. I wouldn't
dream of or imagine that I could run some hi fi in any circumstances.
It's common knowledge that they are multivariate systems with many
parameters which change and are inter dependant.


Alas, the problem for the user or reviewer is that the willingness to
become unstable can depend on factors like the amplifier's inherent output
impedance *inside* the feedback loop. That isn't so easy to characterise
without altering or dissassembling the unit. So checking this can be
detective work.

I have used and tested premium op-amps when designing instrumentation
for medical research and didn't have any difficulty with rf springing
up anywhere along the line. A single high gain block of course is
asking for trouble.

I have spent some years designing and testing audio amplifiers -
commercially, for research, and for personal use. Plus various other
uses of analog amps, signal conditioning, etc, for research and
measurement. So my comments are based on practical experience.

The problem here is partly that domestic hifi amps have to deliver
high powers into undefined loads. The designer has no real idea what
the user will connect to the amplifier - particulary at RF.

Again the audio amplifier should not pass any rf and if it did and it
blew up then the consumer has every right to compensation (my opinion).

The problem here is the meaning of 'pass RF' for various reasons.

If the amp has a large power gain up to 20kHz then that can't vanish
abruptly above that *unless* you have a high order filter somewhere - which
then tends to produce swift changes in phase.

And the unit may have a subsection that can oscillate at RF when the
loadings and drive on other parts is in a given state.

And as I've pointed out, you don't have to explicitly inject RF to make
this happen. They system can do it to itself.

And as for defined loads he should know what is likely to be presented
to his amplifier or for what loads he is designing/selling his
amplifier? It's a cop out to say I'm making an amp but I cant say what
you can do with it. It's a total waste.

You would now need to explain how a designer of commercial domestic audio
power amps would know this. Have a look at a series of reviews of domestic
speakers. Note in particular some of the expensive ones that may have dips
down to an Ohm or so, and phase angles well above 45 deg whilst others go
to high impedances. Note that almost no data is provided for above 20kHz.
Note how much the behaviour varies from one model to the next. Note that
makers keep introducing 'new models' that aren't the same as their old
ones. Then note that a few meters of various unspecified cables will then
completely alter the presented impedance at RF. Out there, anything can
happen... and will.

You can guess what is 'likely'. But if you sell thousands, how many will
find themselves in an 'unlikely' situation over a use life of, say, 10
years. Some of the amps I've been involved with designing are still in use
after more than three times that period. Many have changed hands more than
once. During that lifetime some of the component values will have altered.

And if you assume, say, any phase angle which allows Real to be positive
and modulus bigger than 0.5 Ohms up to 30MHz then the design may be rather
more costly than using weaker assumptions. Perhaps enough so something else
is bought by the customers. So unfortunate if the unpublished unknown
actual results for most speakers were nothing like that demanding at RF.

So designers "should" do all kinds of things. But it might help them if
users realised some of the above. And if the data to base their decisions
upon were actually available. :-)

I know of one case where the user decided the (DIN) speaker socket was the
mains input socket. That even took the track of the board! =8-]

When I designed I ended up assuming that any impedance need to be 'safe' in
the sense of never doing anything worse than blowing a fuse, and the amp
had to be stable unconditionally. But being able to drive low impedances
(and high phase angles) meant I had to ensure the amp could drive very high
currents and powers. So +/- 60V into 2 Ohms, both channels sustained. No
problem - except when the test loads started to melt the benchtop. 8-]

Does put up the cost though, and may be a waste for most customers with
more reasonable speakers.

I think you will know the first rule of purchasing computers, - know
what you want it for then get one that will do the job. That was the
number one maxim before the pc became mainstream.

The problem with analogies to to determine if they are actually relevant or
not. :-)

The problem here is that in terms of your analogy, most sellers of
computers won't actually tell you what you need to know about what the
model can or cannot do. They may not even know. You just are expected to
buy the one that looks 'nicest' in the shop or magazine article and perhaps
the cheapest you think you can get away with using. Good luck. :-)

The situation is often very different in laboratory or
industrial/commercial cases. There you can spec the requirements and
sellers can be expected to give relevant specs for their products. But in
domestic audio most of that data is absent and people just assume it will
either work, or not, on the basis of some 'subjective comments' in a
magazine. Yer pays yer money and yer takes yer chance.

That was one of the main reasons I did the investigations that started this
thread. To raise awareness. I don't doubt that *most* amplifiers in *most*
cases will be fine. But where is the data to tell how many, in which cases,
etc?

I'm always moaning to my wife after a shopping trip how most things are
not properly designed.

I'm still baffled that so many hoovers have pipes that simply pull apart
when you pull the brush towards you. I can understand why they all seem to
be designed for midgets as I fear the designers presume the user will be
female, and female means small. But that becomes doubly daft as their
assumption when you find out how heavy many of the cleaners are. The target
user is presumable a midget strongman, preumably also a magician who can
magic the tubes to stay together. How many cleaners do they sell to
circuses, I wonder... :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

New webpage on loudspeaker cables
 

Jim Lesurf wrote:

I'm always moaning to my wife after a shopping trip how most things
are not properly designed.

I'm still baffled that so many hoovers have pipes that simply pull
apart when you pull the brush towards you. I can understand why they
all seem to be designed for midgets as I fear the designers presume
the user will be female, and female means small. But that becomes
doubly daft as their assumption when you find out how heavy many of
the cleaners are. The target user is presumable a midget strongman,
preumably also a magician who can magic the tubes to stay together.
How many cleaners do they sell to circuses, I wonder... :-)


Jim,

Just a quick thank you from a lurker. That was lovely ;-)