"Don Pearce" wrote in message
...
On Tue, 22 May 2007 23:43:20 +0100, "Keith G"
wrote:

OK. Lemme tell ya summat for nowt...

A short while back I met 'Mr X' when I bought the first of two recent
'bikes and we got on to hifi (as you do). He is/was an avid
'enthusiast'
and had 9 pieces (I'm sure he said) of Cyrus kit, Impulse 'Lali' (?)
speakers and no vinyl - ie *blameless* to a fault (the perfect ukra
paradigm)!

As of now (a number of 'seshes' later) he has 300B SET monos, Lowther
'horns' and (as of yesterday) a Lenco GL75 turntable in natty steel
plinth.

Go figure....

(He still has his CD player, you'll be pleased/relieved to hear!)

Go figure again...

(And I have his colleague's TLS80s... ;-)


And probably the neat little valve preamp I came away with last
night.....



This is all fine. We all love to go into the hall of mirrors at the
fair, don't we?



He hasn't *gone into* the hall of mirrors, he has *moved into* it - the
Cyrus gear has all been sold, I gather.

You need to know I'm not *selling* anything, Don Old (other than when I
*am* selling summat) - when people come here for a listen and start
making better or worse noises, I shrug my shoulders. I have a ton of
*everything* and I like it all - right now is DAB on SS amp, later (much
later if this sun holds) will probably a bit of vinyl on triodes/horns
at some point.

(There's one or two here could do with a trip to the hall of mirrors
when it comes to throwing the 'bigot' word around...)

In article , Rob
wrote:
Don Pearce wrote:
On Tue, 22 May 2007 19:11:40 +0100, Rob
wrote:

But the measurements aren't a substitute for listening - they are
designed to make sure your equipment is not going to mar your
pleasure.

It strikes me that measurement fixation *does* affect listening.

However not all interest in using measurements and understanding their
meanings would be a 'fixation'.

For some, a measured anomaly would take away some of the listening
pleasure even if it was inaudible.

So far as I know, there is no law requiring you to read any of the specs or
measurements for any equipment you buy and use. :-)

However if you actually *understand* the measurements you can easily make
up your mind if any 'anomaly' matters. Indeed, reading and understanding
'measurements' might save you from wasting time money buying a lemon.

A bit like making sure the glass on the front of your
picture is nice and clear... Of course there are those who like
cloudy glass with a coloured tint, but not those who want to see the
whole of the picture.

d

Some people like their glass 'distorted' so they can see the bigger
picture.

Indeed. However it can be useful for them and others to know the cause and
effect involved. This would then give them info useful when they and others
decide what other 'glass' to choose for specific purposes, or to get
results they would feel are a further improvement.

Interestingly, your analogy also implicitly assumes the 'people' know
that the result *is* being 'distorted' by the 'glass', rather than
assuming that what they see is what they'd get if the glass were absent
and their view was direct. The snag in audio is that many people may
have no such awareness, and indeed, no chance to do the equivalent
of seeing the view directly.

Another snag is that in the case of audio there may be many thousands
of different 'pictures' to 'view' and you might like some 'distorted'
by a specific 'glass', but other 'distorted' in other ways. So perhaps
this is simply another attempt at analogy that falls apart once you
try to use it at more that a trivial level. ;-

More generally...

The problem with wilful ignorance is that it gives you no guide if you ever
need to change anything. Similarly, it is no help to anyone else who is
interested in the results you got. Nor does it tell anyone if what is
claimed is for the reasons claimed, or is even real rather than delusional.

I suppose I am old-fashioned. I prefer education and understanding to
ignorance, and I prefer views based on reliable evidence. Indeed, I seem to
get a lot of enjoyment and satisfaction out of learning, understanding,
etc. My experience thus far is that this has helped me to design/choose/use
equipment to allow me to enjoy recorded and broadcast music. I have also
repeatedly found that ideas presented in claims by people have no
foundations, so would probably have wasted my time and impeded my being
able to get to where I have in terms of enjoying the results if I hadn't
had the old-fashioned approach of using measurements, understanding, etc,
to try and find my way though the claims. In my experience this has
complimented listening very well.

So, no, I'm afraid I am not personally a great fan of wilful ignorance as a
policy of choice.

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 Tue, 22 May 2007 16:12:32 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:
On Tue, 22 May 2007 09:19:09 +0100, "Serge Auckland"
wrote:

Indeed, and in my previous post of the criteria, it was stated that THD
should be measured at all frequencies 20-20k and refers to all powers
and all loads for which the amplifier was designed. In practice, the
measurements are actually THD+N as this is what distortion meters
actually measure. Of course the use of a harmonic analyser for
distortion measurement won't pick up the +N component, but as a
practicing engineer, I found the use of such an instrument to be
tedious in the extreme, and unnecessary when an overall THD+N figure
was so easily achieved.

S.


The problem becomes more complex when you use an FFT analyser, as I
suspect most are these days. You then need to consider the number of
points in the FFT, and the way they display noise. Discrete signals are
easy - whatever you do with the FFT, they look the same size, but the
"+noise" bit will change with the number of points.

Erm. It should be the total noise in the audio range. This means that
however many bins it was divided into becomes irrelevant as they are then
summed. Although I'd agree that a small fraction of the noise will be in
the input signal bin and would be 'lost'.

In recent years I've tended to use a Stanford Instruments unit that
combines a test waveform generator and an FFT specan, and 'automates' the
process as you wish. The trick, of course, is to know what process to
specifiy and to understand how to interpret the results - especially when
the spectrum on the screen isn't simple. :-)

The noise floor problem is more significant when reviews simply display the
floor value in terms of the per-bin level without having any clue what
resolution bandwidth they are using. In those cases your comment does
indeed apply, and makes the floors shown in some magazines worthless.
Having tried discuss this with one or two people I fear that this issue
whooshes over the head of some of them. Although there are others who
clearly understand it, but don't use such meaningless plots.


Exactly - although the maths is very easy - just add 10 log (audio
bandwidth / (bin bandwidth * windowing ratio)) to the noise level in
dB. But as you say, this appears to be beyond most people.

The problem is that you must do this to the noise, but not to the
discrete signals, and it can get tricky sometimes separating the one
from the other.

Are there many distortion analysers any more that simply null the
fundamental and display the sum of the rest?

Dunno. The last one I used a lot was the Sound Technology 1000A about two
decades ago. This was very nice, but took a few seconds to settle into a
null, etc, whenever you altered anything. Worked down to about 0.002%
though, IIRC. I think that part of the delay was for the light bulb in the
oscillator to settle when you changed frequency. ;-

Slainte,

Jim

I still have a couple of those tiny bead thermistors in vacuum tubes
that are really good at stabilizing Wien Bridge oscillators. Better
than light bulbs, I think.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Tue, 22 May 2007 16:03:55 +0100, Jim Lesurf
wrote:

In article , Serge Auckland
wrote:


"Jim Lesurf" wrote in message
...


I'd also tend to use a THD+Noise value as otherwise effects like PSU
intermod might be missed as their components don't crop up at
harmonics of the test frequency in most cases. I've seen amps where
the THD value was low, but where there was much more LF garbage due to


Indeed, and in my previous post of the criteria, it was stated that THD
should be measured at all frequencies 20-20k and refers to all powers
and all loads for which the amplifier was designed. In practice, the
measurements are actually THD+N as this is what distortion meters
actually measure. Of course the use of a harmonic analyser for
distortion measurement won't pick up the +N component, but as a
practicing engineer, I found the use of such an instrument to be
tedious in the extreme, and unnecessary when an overall THD+N figure
was so easily achieved.

Well, I've used both 'traditional' THD+N kit that works by nulling or
filtering the test sinusoid, and a specan/generator that autofinds the
harmonics and works out THD. The second didn't seem at all 'tedious' to use
as it automated the process. It was also faster than the old distortion
kits I used to use that took some seconds to null down for low distortion.

I suspect that people use either form of kit, whichever is to hand. The
difficulty with this being what we discuss above.

Slainte,

Jim

There is a distinct advantage to the second, in that it gives you
information about the nature of the harmonics. If you are making this
measurement as part of a development process, that can be invaluable.

d

--
Pearce Consulting
http://www.pearce.uk.com

On Wed, 23 May 2007 09:05:56 +0100, "Keith G"
wrote:


"Don Pearce" wrote in message
...
On Tue, 22 May 2007 23:43:20 +0100, "Keith G"
wrote:

OK. Lemme tell ya summat for nowt...

A short while back I met 'Mr X' when I bought the first of two recent
'bikes and we got on to hifi (as you do). He is/was an avid
'enthusiast'
and had 9 pieces (I'm sure he said) of Cyrus kit, Impulse 'Lali' (?)
speakers and no vinyl - ie *blameless* to a fault (the perfect ukra
paradigm)!

As of now (a number of 'seshes' later) he has 300B SET monos, Lowther
'horns' and (as of yesterday) a Lenco GL75 turntable in natty steel
plinth.

Go figure....

(He still has his CD player, you'll be pleased/relieved to hear!)

Go figure again...

(And I have his colleague's TLS80s... ;-)


And probably the neat little valve preamp I came away with last
night.....



This is all fine. We all love to go into the hall of mirrors at the
fair, don't we?



He hasn't *gone into* the hall of mirrors, he has *moved into* it - the
Cyrus gear has all been sold, I gather.


I wonder - will he stay there, though?

You need to know I'm not *selling* anything, Don Old (other than when I
*am* selling summat) - when people come here for a listen and start
making better or worse noises, I shrug my shoulders. I have a ton of
*everything* and I like it all - right now is DAB on SS amp, later (much
later if this sun holds) will probably a bit of vinyl on triodes/horns
at some point.


I've given up listening to DAB at home - it is just too unpleasant.
When I want to listen to the wireless, I use Freeview (except when I
am sat here at my PC, in which case it is an AM/FM clock radio I got a
million years ago with my Esso Tiger tokens).

(There's one or two here could do with a trip to the hall of mirrors
when it comes to throwing the 'bigot' word around...)



Life is far too short to get wound up about all this stuff, really.


d
--
Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote


This is all fine. We all love to go into the hall of mirrors at the
fair, don't we?



He hasn't *gone into* the hall of mirrors, he has *moved into* it -
the
Cyrus gear has all been sold, I gather.


I wonder - will he stay there, though?


Dunno, what's scary is how he's ditched everything he had and made the
complete 'leap of faith'!! Myself, I operate at least a 'one on and one
in the wash' MO and have 7 or 8 different stereo amps here, just for
starters....




You need to know I'm not *selling* anything, Don Old (other than when
I
*am* selling summat) - when people come here for a listen and start
making better or worse noises, I shrug my shoulders. I have a ton of
*everything* and I like it all - right now is DAB on SS amp, later
(much
later if this sun holds) will probably a bit of vinyl on triodes/horns
at some point.


I've given up listening to DAB at home - it is just too unpleasant.


Whilst FM on the TLS80s can be just a bit too much of everything
here....

goes to check

Nope, it's fine and I've left it on! Must be the weather!



When I want to listen to the wireless, I use Freeview (except when I
am sat here at my PC, in which case it is an AM/FM clock radio I got a
million years ago with my Esso Tiger tokens).


My most-used bit of 'audio kit' is a wooden-cased Bush 'old style' radio
which I must have had for 20 years (significant birthday present) - it
gets used every single day at some point!



(There's one or two here could do with a trip to the hall of mirrors
when it comes to throwing the 'bigot' word around...)



Life is far too short to get wound up about all this stuff, really.


I think so, but you've got to counter their hot little faces and their
silly little 'attacks' with summat, ain'tcha? ;-)

(It's only fekkin' *hifi* at the end of the day!!)

"Jim Lesurf" wrote in message
...
In article , Serge Auckland
wrote:


"Jim Lesurf" wrote in message
...


I'd also tend to use a THD+Noise value as otherwise effects like PSU
intermod might be missed as their components don't crop up at
harmonics of the test frequency in most cases. I've seen amps where
the THD value was low, but where there was much more LF garbage due to


Indeed, and in my previous post of the criteria, it was stated that THD
should be measured at all frequencies 20-20k and refers to all powers
and all loads for which the amplifier was designed. In practice, the
measurements are actually THD+N as this is what distortion meters
actually measure. Of course the use of a harmonic analyser for
distortion measurement won't pick up the +N component, but as a
practicing engineer, I found the use of such an instrument to be
tedious in the extreme, and unnecessary when an overall THD+N figure
was so easily achieved.

Well, I've used both 'traditional' THD+N kit that works by nulling or
filtering the test sinusoid, and a specan/generator that autofinds the
harmonics and works out THD. The second didn't seem at all 'tedious' to
use
as it automated the process. It was also faster than the old distortion
kits I used to use that took some seconds to null down for low distortion.


When I was designing audio equipment, I never had the luxury of an
autofinder, the one I used was a Marconi Instruments meter which in effects
was a highly selective filter and meter, and to use it, one found each
harmnic individually, measured its level, then worked out the THD by
algebra. As I said, tedious in the extreme. I much preferred the Radford
LDO/DMS combination, or the Ferrograph for a quick and dirty measurement.

More recently, I had the use of a Lindos LA100 test set, which measured THD
automatically, and printed out the results or sent a file to a PC. Sadly, I
couldn't keep it when I left the company.

S
--
http://audiopages.googlepages.com

In article ,
Don Pearce wrote:
I've given up listening to DAB at home - it is just too unpleasant.
When I want to listen to the wireless, I use Freeview (except when I
am sat here at my PC, in which case it is an AM/FM clock radio I got a
million years ago with my Esso Tiger tokens).

Are you really saying that sounds better than DAB through a decent system?
;-)

--
*Would a fly without wings be called a walk?

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

On Wed, 23 May 2007 11:00:41 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
I've given up listening to DAB at home - it is just too unpleasant.
When I want to listen to the wireless, I use Freeview (except when I
am sat here at my PC, in which case it is an AM/FM clock radio I got a
million years ago with my Esso Tiger tokens).

Are you really saying that sounds better than DAB through a decent system?
;-)

No - it sounds bloody awful - but in a way I can accept. DAB, through
a decent system is what I would use to settle down to serious
listening. For that it is totally unacceptable.

d

--
Pearce Consulting
http://www.pearce.uk.com

In article , Don Pearce
wrote:
On Tue, 22 May 2007 16:03:55 +0100, Jim Lesurf
wrote:


Well, I've used both 'traditional' THD+N kit that works by nulling or
filtering the test sinusoid, and a specan/generator that autofinds the
harmonics and works out THD. The second didn't seem at all 'tedious' to
use as it automated the process. It was also faster than the old
distortion kits I used to use that took some seconds to null down for
low distortion.


There is a distinct advantage to the second, in that it gives you
information about the nature of the harmonics. If you are making this
measurement as part of a development process, that can be invaluable.

When using the ST1000A I used to find it useful to view the result of the
nulling on a scope. i.e. the waveform with the test sinusoid removed. This
gave similar info provided you could 'interpret' the results. For example,
very useful when adjusting the bias of an AB output as you could see any
crossover error appear or vanish as you twiddled the bias.

This has an advantage over power/frequency plots of the harmonics as it
shows the effects of the relative phases as well. If I still had an ST1000A
I'd probably be using it, but I lost access to it 20+ years ago...

FWIW A month or two ago I wrote a simple example program that does this for
a computing magazine. Found it quite interesting to view the nulled
patterns from an old Shure cart playing a test LP.

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