A bit of history.
 

Nick Gorham wrote:
The interesting thing there, is the statement that because it seems some
may prefer 2nd harmonics, this means that it "casts doubt on subjective
testing", not that it casts doubt on the validity of the measurement of
distortion :-)

In other words, the people who prefer the distortion are wrong,

Of course not but they cannot use the sound they prefer to judge how
well an amplifier is performing.

and they should be ignored.

If they are using this to judge the performance of the amplifier then
probably. If they are using it to judge what sound they prefer then
probably not.

And it clearly indicates that his goal was the
production of an amplifier that measured well, not one that people liked
to listen to.

Measured well is perjorative but essentially correct. The function of
an amplifier is to amplify the signal without distortion. If you want
to amplify the signal and distort it in a nice sounding way then all
competent engineers and rational people will separate the two functions
and assess them separately.

A bit of history.
 

In article , Nick Gorham
wrote:
Eiron wrote:
I was looking at 'Audio Electronics' by the late John Linsley Hood
this morning while waiting for the newspaper to arrive, and was
amused by this:

" Experiments in the late 1940s suggested that the level of audibility
for second and third harmonics was of the order of 0.6% and 0.25%
respectively, and this led to the setting of a target value, within
the audio spectrum, of 0.1% THD, as desirable for high quality audio
equipment. However, recent work aimed at discovering the ability of an
average listener to detect the presence og low order (i.e. second or
third) harmonic distortions has drawn the uncomfortable conclusion
that listeners, taken from a cross section of the public, may rate a
signal to which 0.5% second harmonic distortion has been added as
'more musical' than, and therefore preferable to, the original
undistorted input. This discovery tends to cast doubt on the value of
some subjective testing of equipment."

So the SET set is right. single-ended valve amps are officially 'more
musical'.


The interesting thing there, is the statement that because it seems some
may prefer 2nd harmonics, this means that it "casts doubt on subjective
testing", not that it casts doubt on the validity of the measurement of
distortion :-)

I am not sure that is the correct interpretation of the wording. However I
haven't checked the context.

When the above says "may rate a signal" the implication seems to me that
this varies according to either the individual and/or the specific material
being played. Note the word "may", not "will".

The point then would be that it "casts doubt" on subjective testing because
the subjective opinions expressed may not be useful to the reader of said
opinions, for reasons not made clear in the report of the subjective
testing report.

FWIW This has always seemed to me to be a critical weakness of many
'subjective reviews'. Even if they reliably describe the opinions of the
reviewer, it is not clear if the reader would agree with them. Any
differences in circumstances or personal details might make the subjective
comments worthless to the reader. and they might have no way to judge...

Unless, of course, they do their own assessement. But if the 'test report'
is so unreliable as to mean we have to always do this, then the review in
practice has zero useful content for readers. What point is there in a
'subjective report' from someone else if we find that it is just as
likely to mislead us as not, so we end up having to decide for
ourselves, regardless of such reviews.

The above tends to be made worse when said reviews don't employ any
sensible experimental protocol. Then, the conclusions in the report
of the review might actually not even be valid for the reviewer,
either, as they may simply be misleading themselves.

The view that some people may prefer the results when some form of
nonlinarity (or other systematic alteration) is imposed isn't exactly a
revelation, though. People have been commenting on this for decades so far
as I can recall.

Above said, I have reservations about some of the tests which have led
to 'conclusions' like the above. For example: How did they ensure the
speakers they used provided levels of nonlinearity way below the levels
they were trying to assess? It is all to easy when people run such 'tests'
to focus on one area and forget others that may be affecting (or even
swamping) what they are doing.

In other words, the people who prefer the distortion are wrong, and they
should be ignored. And it clearly indicates that his goal was the
production of an amplifier that measured well, not one that people liked
to listen to.

As above, it would depend on how you interpret his wording. :-)

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

A bit of history.
 

In article ,
Eiron wrote:
In the late '40s the public would not have heard anything approaching
what we consider normal these days for sound reproduction - there was
only AM radio restricted by the lines feeding the transmitters to
about kHz, and of course 78 rpm records. And pretty well all
reproducers used single unit speakers - often large. Amplifiers were
invariably SET. So their perception of what was or wasn't musical was
influenced by what they were used to.

Maybe not what you would call hi-fi, but the public could actually
listen to jazz bands, orchestras, organ recitals and choral works.

They could indeed. But very few get a chance to compare the recorded sound
*at the same time* and the ear's 'memory' is poor.

And they did have access to Tannoy dual-concentrics and Leak or Quad
push-pull amps.

In the '40? I think not.

--
*There are two sides to every divorce: Yours and **** head's*

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

A bit of history.
 

In article ,
Keith G wrote:
See elsewhere, where I mentioned a visitor was here from 11:30 am to
9:30 pm listening to the Holy Trinity (SET/vinyl/horns) on Thursday -
guess what, he was here again yesterday afternoon for another 3
hours.....!!!

You've found a kindred spirit. Of course I assume he knew what he was
coming to listen to?

--
*Make it idiot-proof and someone will make a better idiot.

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

A bit of history.
 

In article ,
Tony Gartshore wrote:
I still listen to my Linsley Hood 75w power amp, 0.01% distortion at
any level up to clipping. I like to listen to it.

Listening to R4 at the moment via one driving a pair of home assembled
LS 35/a...

Blimey, I wonder if mine's still up in the loft?
How would it pair with JR149s I wonder ?

It's a decent amp which will drive pretty well any MC speaker.

--


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

A bit of history.
 

"Dave Plowman (News)" wrote in message
...
In article ,
Keith G wrote:
See elsewhere, where I mentioned a visitor was here from 11:30 am to
9:30 pm listening to the Holy Trinity (SET/vinyl/horns) on Thursday -
guess what, he was here again yesterday afternoon for another 3
hours.....!!!

You've found a kindred spirit.



I've probably found a *dozen* of them so far!! ;-)


Of course I assume he knew what he was
coming to listen to?


You tell me, here's an extract from his email (which came via the WD forum -
verbatim cut & paste but *confidentialised*):

-----------------------------------------------
This is the message:

Reading through one of your posts you let slip you were living in sunnny St.
Neots.

I live up near the rainbow superstore at No XXXXXXXXXXXXX.

I have been a nut since about the age of 13. have built several reflex boxes
over the years and had a play with my own designs.

Right now am completely lost what to do next, and have very little time to
spare as I work away during the week.

I have a cople of turntables cartridges, icon audio and quad 2 amps.

I would be interested in having a chat or a beer with you regarding technics
direct drive TT and your experiences with set's and single driver
enclosures. However your website stuff may say it all.

Home tel no is 01480 XXXXXX

Regards,
XXXXXXXX
ps. I have been a memeber of the bulletin baord for a couple of years now, I
have more fun reading alll the diverse things in there than posting and dont
feel upto posting on technical stuff.
-----------------------------------------------

Don't know why he said he doesn't feel up to posting stuff - he's an
electronics engineer (real/active/working/UK/Middle East/Far East/US), knows
Tim de P and gawd knows who else and certainly knows his stuff
'techiewise'...!!

When he phoned yesterday afternoon (he's had the last week off on holiday
and is/was obviously kicking his heels) he asked what I was up to? I told
him I had finally got round to ripping the arse out of the Bez amp
(intermittent right channel which came and went when you rocked the valve -
his visit had prompted me to get it sorted) and was about to try and sort it
out. He said 'Ooh, do you want me to pop round?' I said 'I got an EE on the
phone and a valve amp that needs a bit of TLC?' I guess it might not be such
a bad idea!! :-)

He was on the doorbell by the time I had put the phone down!! OK, not true
actually - I had flowed the joints on the valve socket by the time he
arrived which had not solved the problem. I then got an elbow in my chest
when he arrived and he found a broken solder joint in about 5 minutes of
poking about/measuring while I wuz on the phone!!

(I hope that wasn't too *bloggy* for you...?? ;-)



*** Note to Phil N - if you are reading this, we can take your Ming Da round
(3 mins from here) and hook it up to his Icon Audio to see if there's a
*match* - drop me a line!! (Looks like they come out of the same factory -
he studied the pix of **Ming The Terrible** on my 'puter and said it all
looks very familiar..!!??)

A bit of history.
 

"Eiron" = a PITA idiot


I was looking at 'Audio Electronics' by the late John Linsley Hood this
morning
while waiting for the newspaper to arrive, and was amused by this:

" Experiments in the late 1940s suggested that the level of audibility for
second and third harmonics was of the order of 0.6% and 0.25%
respectively,


** Such tests were generally done with independent sound sources for the
harmonic tones. In essence, the test is of the masking effect of the
fundamental tone on low numbered harmonics.

Has virtually NOTHING to do with the assessing audible effect of non
linearity on a music signals - since inharmonic tones ( ie sum and
difference products) were not included.


and this led to the setting of a target value, within the audio spectrum,
of
0.1% THD, as desirable for high quality audio equipment.


** Not strictly true.

Producing audio amplifiers that gave reliably under 0.1% THD across the band
proved to be far from easy - however once achieved ( by the Leak Point One)
it became the de-facto standard.

All the BIZARRE and OBSESSIVE audio spec chasing we see today comes
directly from this phenomenon.



However, recent work aimed at discovering the ability of an average
listener
to detect the presence og low order (i.e. second or third) harmonic
distortions
has drawn the uncomfortable conclusion that listeners, taken from a cross
section of the public,


** There is the #1 problem: " ... a cross section of the public, ".

Not experienced listeners.


may rate a signal to which 0.5% second harmonic
distortion has been added as 'more musical' than, and therefore preferable
to,
the original undistorted input.


** Typical hi-fi speakers have at more than 0.5% THD even at moderate
levels.

Or did the testers use headphones - maybe ES ones ?

Was the 0.5 % being added to a really clean signal or an already polluted
one?

With no such important details, the info is utterly WORTHLESS as evidence.



This discovery tends to cast doubt on the value
of some subjective testing of equipment."


** What a non-sequitur !!!!

The value of such testing has ALWAYS been in ENORMOUS doubt !!


So the SET set is right. single-ended valve amps are officially 'more
musical'.


** Only to demented tubehead dopes.





........ Phil