The discussion on the new page has prompted me to do something I'd be
meaning to get around to for a while, and to (at last!) add some extra link
buttons to the 'HFN' set of pages. :-)

I have therefore now added link buttons to the bottom on most of the pages
that are based on HFN articles. These should make it easier for readers to
move to 'previous' or 'next' ones in any series. Should help people find
details on one page that aid understanding others.

Given later supply of 'round tuits' I may do some more linking for other
pages, and perhaps in due course add a 'technical sidebar' page for some
items that goes into detail of how results were obtained. I often already
have these in rough note forms but omitted from published articles in HFN
due to the density of 'hard sums' or the need for the reader to follow the
details of the relevant engineering or physics. But they may be useful for
some readers.

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

On Fri, 07 Aug 2009 09:10:40 +0100, 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.

Slainte,

Jim

Skin effect at audio frequencies?? Haven't you described this as resulting
in about 0.02dB loss at 25kHz over near dc? hardly noticeable unless
you're a Vulcan :-)
At my age (50's) my auditory system is so shot I'm glad I can still hear
sounds above the tinnitus.

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.

Ducks behind potted plant.

Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"John" wrote in message
...
On Fri, 07 Aug 2009 09:10:40 +0100, 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.

Slainte,

Jim

Skin effect at audio frequencies?? Haven't you described this as resulting
in about 0.02dB loss at 25kHz over near dc? hardly noticeable unless
you're a Vulcan :-)
At my age (50's) my auditory system is so shot I'm glad I can still hear
sounds above the tinnitus.

On Thu, 13 Aug 2009 18:08:53 +0100, Dave Plowman (News) wrote:

In article ,
Eeyore wrote:
You have my 100% agreement again. Is Jim Lesurf one of those
out-of-touch academics that never have to build a product that has to
work in the real world ?

I'll answer for Jim in case he's modest. He designed a variety of amps for
Armstrong which were very well regarded. I had experience of a tuner amp
which sounded very good indeed.

That may be so but all the guff about skin effect at audio frequencies is
only of relevance to the sport of measurement - you'll never hear the
difference.


What well regarded commercial designs are you responsible for?

On Thu, 08 Oct 2009 10:11:47 +0000, Brian Gaff 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.



Ducks behind potted plant.

Brian

On Sun, 16 Aug 2009 09:32:22 +0100, Jim Lesurf wrote:

In article , David Looser
wrote:
"Eeyore" wrote in message
...

Perhaps you'd like to explain exactly how the techniques you have
used to ensure unconditional stability are an improvement on those
used by Jim in his designs for Armstrong.

(a) I don't have the time.

(b) It's commercially confidential.

Yeah, yeah. Excuses excuses.

Going off a tangent: I must admit I found (b) above quite interesting/
amusing. There does seem to have been a trend in recent decades for makers
and desigers to feel that physics and engineering can somehow be kept
'secret'.

A few decades ago makers of items like hifi amps and tuners where happy to
let users have circuit diagrams and explain to people how their equipment
worked. They were proud of what they had built, and wanted to explain its
ingenuity. Indeed, in my exprience they generally felt that open
discussions with other engineers about what they had done would help
everyone to improve. And they had the confidence that they would have new
ideas and improve as they learned.

More recently there has been a tendency to treat circuitry as being a
'commercial secret', perhaps even extending to behaviour like removing the
printing from some components so others can't read the part numbers. I
even read reports some time ago of a well-known designer putting ball
bearings into the potting of his output transfomers to stop anyone opening
them up to see what he had done.

Afraid that to me this behaviour seems to betray a lack of confidence in
their work, and in their ability to have newer or better ideas later on,
perhaps even almost paranoia in extreme cases. It seems odd to me as it
seems like a belief that others are frantic to 'steal' their 'idea',
rather than being quite capable of doing things for themself. Perhaps in
some cases a form of self-flattery to think others would need to do so.

I have often wondered if this obsession with 'secrecy' over matters which
could usually be uncovered *if* some other skilled engineer with resources
*wanted* to reverse-engineer what had been done is a factor in the growth
of 'snake oil' as it feeds ignorance amongst users and may help
technobabble to flourish.

Perhaps this is a factor in the way users have been led to treat some
designers and makers as 'magicians' who practice a magic art beyond the
ability of mere mortals to understand.

When I worked in audio I and other designers at other companies quite
happily exchanged ideas, and loaned circuits to each other. I guess it may
be very different now. If so, it may well impede the education of some
designers as they will find help from their peers harder to obtain.


My personal view is that if you buy something, then it is yours, and with
that you should be entitled to have the info to allow you to understand
how it works or alter it if you so prefer. So in another area my
preference for Linux and the approach of its community to software. And in
electronics, a wish for full technical onfo on any item I might want to
buy/use. Perhaps this is the 'academic' in me wanting to understand
things. Maybe it is that I object to being told, "we want your money, but
you can only use the item, not be allowed to try and understand how it
works." I've had various items of 'consumer equipment' which have broken
and are then impractical to repair as the makers won't release info or
parts. So there may also be what seems like a scam here to me, causing
repairable or improvable items to end up as landfill.

I wonder how many computers will end up as landfill as a result of people
feeling "Must have Windows 7 to follow everyone else"?...

...but that is well OT. :-)


So coming back on topic, the above does rather support my wondering if all
current/recent amplifiers are as good as they *could* be if their
designers/ makers were more open, and less fearful of others being able to
study what they had done.

Slainte,

Jim

I've seen instances where builders have rubbed off component markings.
They are not very common though. What I'd like to say is this, I think
that design today is more about fashion than practicality. Looks and form
over function. You can see it everywhere.

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. 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).



And since when ( Fig 1 for example ) do you run a cable open or shorted as
a valid test ?

WHAT A COMPLETE HEAP OF MINDLESS JUNK !

You should be ashamed of yourself and run some REAL models.

Graham

In article , John
wrote:
On Thu, 13 Aug 2009 18:08:53 +0100, Dave Plowman (News) wrote:

In article , Eeyore
wrote:
You have my 100% agreement again. Is Jim Lesurf one of those
out-of-touch academics that never have to build a product that has to
work in the real world ?

I'll answer for Jim in case he's modest. He designed a variety of amps
for Armstrong which were very well regarded. I had experience of a
tuner amp which sounded very good indeed.

That may be so but all the guff about skin effect at audio frequencies
is only of relevance to the sport of measurement - you'll never hear the
difference.

I presume you missed the comments I made about this at the time.

However the page had two overall main purposes.

1) To investigate cable+load combination behaviour at ultrasonic/RF
frequencies that can, indeed, affect amplifier behaviour in ways that can
be both audible and measurable at *audio* frequencies. e.g. problems with
lack of stability into some presented loads.

2) To use the values obtained by the ultrasonic/RF measurements as one of
the methods to work out the cable capacitance, inductance, etc. Which again
can affect the results at audio frequencies in ways that can be both
audible and measurable. Did this because attempts to measure short run C
and L values are tricky at LF and also prone to the problem that the values
do alter with frequency. So did measurements by various methods to obtain
cross reference and reliability.

Skin effect was included, because internal impedance does indeed influence
behaviour and so is part of the above. In most cases 'skin effect' isn't
likely to be audible. But the difference it makes from one cable
design/length/load case to another might upset one amp audibly, but not
another. So it can matter.

If you have not already done so, I'd recommend you read the previous
articles in the series (hint: this one was 'cables3' :-) ) as that may help
make these points clearer. The 'cables3' article *is* part of a series, so
just reading the one page is a bit like reading one page of a book and then
complaining it doesn't make sense (because you don't know the context).

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

In article , John
wrote:
On Sun, 16 Aug 2009 09:32:22 +0100, Jim Lesurf wrote:


I have often wondered if this obsession with 'secrecy' over matters
which could usually be uncovered *if* some other skilled engineer with
resources *wanted* to reverse-engineer what had been done is a factor
in the growth of 'snake oil' as it feeds ignorance amongst users and
may help technobabble to flourish.

I've seen instances where builders have rubbed off component markings.
They are not very common though. What I'd like to say is this, I think
that design today is more about fashion than practicality. Looks and
form over function. You can see it everywhere.

I would agree. However I've often found both good, and bad, designs in
terms of performance. And the responses I got to the page(s) you mentioned
did support my impression that some makers/designers may still not ensure
their designs are unconditionally stable.

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

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.

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

1) never buy or use any audio amplifiers.

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.

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.

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.

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