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In article ,
Eeyore wrote:
As usual you have jumped straight in without reading and digesting the
article.

The effect of pure shorts and opens is an ASININE concept, completely
out of touch with the real world.

Nothing wrong in covering everything on such an article. As certain
speakers may well *tend* towards a short or OC at certain frequencies.
It would be an entirely different matter if this research was being used
to sell or promote some product.

--
*Why is 'abbreviation' such a long word?

Dave Plowman London SW
To e-mail, change noise into sound.

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In article , 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.

I didn't comment for two main reasons.

1) That so far as I could see Eeyore was simply playing a "go for the man
not the ball" debating tactic to avoid dealing with his lack of
understanding of what I'd actually been saying. I would prefer people
actually focussed on the technical issues, not "My Dad is bigger than your
Dad". :-)

2) Afraid that I now have no idea how many amps Armstrong sold. The records
were binned decades ago. alas. Long before I decided to collect info for
the webpages about Armstrong. The numbers would certainly be in the many
thousands just from recalling the production rate on the line that was
outside my old office there. My best estimate would be a few tens of
thousands per year when I was there. But I doubt there is any record now.
When I asked the old production/line managers some years ago they could not
recall. This is a shame as I would have liked to be able to provide users
with info on things like when various mods or improvements were made and
link that to date and seriel number. But all that data has gone.

Nor TBH is it for me to say if anything I did is "well regarded" or not!

I'm afraid that so far as I can see, Eeyore's assertions mainly show that
he simply does not understand the measurement method I used for the
article, nor why I used it. In effect he hasn't read the article but is
imagining a set of `meanings' for it of his own invention. Hence the
various statements he has made which simply don't represent its content or
intent. Fortunately, for those who *do* understand these things, what he
says does make clear his failure to understand.

I have now tried more than once to explain this in the hope that he would
then realise his initial misunderstanding. I can appreciate that some audio
engineers may not know much about some of the measurement methods as they
are more common in measurement labs for other purposes. But it looks like
he still misunderstands, so I think it best to decide it would be a waste
of time to try again to explain these things. He does not seem to be
listening.

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

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"Dave Plowman (News)" wrote:

Eeyore wrote:
As usual you have jumped straight in without reading and digesting the
article.

The effect of pure shorts and opens is an ASININE concept, completely
out of touch with the real world.

Nothing wrong in covering everything on such an article. As certain
speakers may well *tend* towards a short or OC at certain frequencies.
It would be an entirely different matter if this research was being used
to sell or promote some product.

Which is why I suggested putting PRACTICAL inpedance limits on the load being
driven.

Graham

--
due to the hugely increased level of spam please make the obvious adjustment
to my email address

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Jim Lesurf wrote:

Eeyore wrote:
"Dave Plowman (News)" wrote:

As usual you have jumped straight in without reading and digesting the
article.

The effect of pure shorts and opens is an ASININE concept, completely
out of touch with the real world.

Thanks, Eeyore. :-) You have just confirmed that you haven't understood
that their use is part of a standard *practical* technique for impedance
measurements. That largely explains your failure to understand the content
of the article.

You are quite mad. I don't think you'd understand the meaning of 'practical' if
it stood up and smacked you in the face.

Graham


--
due to the hugely increased level of spam please make the obvious adjustment to
my email address

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"Dave Plowman (News)" wrote:

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.

The name Armstrong dates his knowledge massively.


What well regarded commercial designs are you responsible for?

Studiomaster Mosfet 250 ( also used in a powered mixer )
Studiomaster 1200B Mosfet Amp ( 2 x 600 W into 4 ohms )
Studiomaster 300B and 600B bipolar amps ( 600B also used in a powered mixer )
Studiomaster 700D/1200D/1600D/900E/1500E/2000E bipolar ( several of those also
being used in powered mixers too )

The 1600D was 2x800W into 4 ohms and the 2000E 2x1000W into 2 ohms.

Studiomaster AX series bipolar.

Many of the above also included useful functions such as 'clip limiters' and
fully variable speed cooling and you'll find many of them on ebay uk in
particular.

I bought 2 x 10 year old D series for friends for a snip on ebay and they were
still in excellent condition and still working today.

Graham

--
due to the hugely increased level of spam please make the obvious adjustment
to my email address

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"Eeyore" wrote in message
...


The name Armstrong dates his knowledge massively.


The principles were exactly the same then as they are now. In addition the
stuff he has posted here shows that he has a level of understanding of those
principles that go well beyond yours.

David.

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Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
Eeyore wrote:
Don Pearce wrote:
Eeyore wrote:
Jim Lesurf wrote:
Rob wrote:
Jim Lesurf wrote:

FWIW it means very little to me. You seem to assume a correlation
between frequency, resistance and sound.

Not sure what you mean, I'm afraid.

That much is apparent. Doubt you know much about the concept at all, nor the
bases of stability.

Can you explain then? It has me puzzled too. And given Jim's
background I am going to tell you he knows precisely what stability
means, and how to measure and predict it.

How many amps has Jim designed that have sold in the many tens of thousands ? And
been VERY reliable.

I don't see any relevance in this answer.

Practical knowledge of how to do it and get it right.

So, how many amps has Jim sold commercially ?


How many marginally stable amps have you designed?

None.


I'm betting you have no idea, because your technical description of how to get it
right in another post was utterly wrong.

I'd love to hear your idea then !


It is clear that not only did
you not understand the mechanisms involved,

Of course I do. I was taught it over 30 yrs ago.


but your approach was simply design and hope (I suspect application notes and cookbooks

figured largely).

I expect my designs are way in advance of even the best of the application notes. I also
use simulation extensively now to refine the method and was doing so first using MathCad
20 years ago.


When I reworked a 'semi-clone QSC' Chinese OEM amp that was less than ideal I did so
using very few extra parts, smarter tracking and different compensation. When I finally
met one of the company's employees he commented " nice job you did on the AX series ". It
also no longer had the QSC faults.

You've never seen my work btw, so you're in no position to comment.

Graham


--
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address

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Jim Lesurf wrote:

Dave Plowman (News) wrote:
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.

I didn't comment for two main reasons.

1) That so far as I could see Eeyore was simply playing a "go for the man
not the ball" debating tactic to avoid dealing with his lack of
understanding of what I'd actually been saying. I would prefer people
actually focussed on the technical issues, not "My Dad is bigger than your
Dad". :-)

2) Afraid that I now have no idea how many amps Armstrong sold. The records
were binned decades ago.

When did you last design an amp for commercial production and what was the fT
of the output devices ?

I suspect you're living in an ancient world that has no relation to today's
designs.

Graham

--
due to the hugely increased level of spam please make the obvious adjustment to
my email address

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"David Loser is a know nothing LIAR"

"Eeyore"


The name Armstrong dates his knowledge massively.


The principles were exactly the same then as they are now.


** You would not recognise a principle if it bit you - arsehole.


In addition the stuff he has posted here shows that he has a level of
understanding of those principles that go well beyond yours.


** True indeed.

Jim's thinking is in fact goes way beyond planet earth, right out into the
galaxies inhabited by strange alien beings and pointy headed pixies floating
on clouds made of Opium smoke.

http://www.fliktalk.com/wp-content/u...nderland-6.jpg




..... Phil

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


The name Armstrong dates his knowledge massively.


The principles were exactly the same then as they are now. In addition
the stuff he has posted here shows that he has a level of understanding
of those principles that go well beyond yours.

I can't be sure, but my impression is slightly different to that. I see no
reason to doubt that Eeyore understands how to design stable amplifiers,
and why it is important to do so. Alas, what he writes shows that he
persistently fails to understand the measurement method I employed to
determine the *cable* properties, and how that can produce results like
CRLG values that also apply for audio signals, etc.

It may well be the case that I am familiar with measurement methods that
he, and perhaps audio-only engineers in general, don't usually encounter.
But I see no reason to doubt that he could understand and appreciate the
use of the methods *if* he so chose.

The problem is that, having misunderstood, he chooses instead to attack
what he misunderstands rather than stop to even consider the possibility
that he may have missed the point. There are good practical reasons for
doing measurements here that extend into the RF region and using a set of
test loads that include 'open' and 'short', but he seems unwilling to even
stop and try to understand why that may be so. Instead he keeps reacting on
the basis of missing the point and jumping to conclusions.

Hence, for example, the way he has repeatedly presumed I hold views which I
do not, and to adopt "My Dad is bigger than your Dad" as if that were a
test of what I had written in the article(s). In essence he is boxing
shadows of his own invention, whilst ascribing them to me, rather than
ensuring he understood I have actually done...

Whilst he persists in this there isn't much I can do to sort out his
confusion, I'm afraid. I can't explain to someone who refuses to listen. I
have tried to explain this to him more than once, and have had to conclude
that this was a waste of effort. I feel this is a pity, but there isn't
much I can do about it as things stand.

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