New page on Squares waves and amplifier performance
 

Ian Iveson wrote:
bcoombes wrote:



The likes of Hi-Fi News now pander to the ignorant by merely
convincing them they've learned something, which apparently
is not hard to do.

As you can see in recent threads see I'm not a subscriber to the view that
everything that needs to be known about audio is known, on the other hand when
I read a review that calls an amp an "urgent and frisky sounding musical tool"
(Decembers Hi-Fi World) I can't help chuckling and wondering who the 'tool'
really is. :)

New page on Squares waves and amplifier performance
 

Jim Lesurf wrote:

The cd-player source argument is a red herring, surely?

Not sure what you mean. It was one of the domestic sources
used purely as
an example of the kind of signal source normal users will
be rather more
likely to be listening to than a test-bench squarewave
generator.

I mean that the cd player is irrelevant because no-one would
use one now, or then, as a source for a square wave test.
It's not as if suitable sources are no longer available or
inferior to what they were, so what could the source have to
do with the disappearance of the test?

Listening to square-wave generators was no more common then
than now, either, so there's another red herring.

Especially combined with the arbitrary example of a 5k
square wave. 1k
would give you plenty harmonics, especially if you
weren't daft and used
a proper source.

Erm, the point isn't just having 'plenty of harmonics'. It
is the finite
bandwidths, slew rates, current demands, etc. And how
these can be somewhat
different for ordinary domestic examples than for a bench
test of the kind
that was once routine.

I can't quite see how those two sentences fit together, or
what you intend to mean by either of them.

What I meant was that, when you argue that a cd source can
only accomodate one of the odd harmonics necessary for a
decent 5k square wave, it can support nine odd harmonics of
1k, which is plenty for a quite good 1k square wave, and a
half-decent generator that could be easily acquired by a
reviewer will likely offer a squarer square wave than one
used by reviewers or DIY-equipped readers in the past. In
short, the quality of the source appears to me to have no
bearing whatsoever on the demise of the square-wave test.

Also, as mentioned in the preamble, this was prompted by
looking at
material on loudspeaker cables of tests using bench
sources which brought
to my mind the way similar things were done in the past in
reviews, etc.

You conclude that reviewers have abandoned the square
wave, but did
they ever use it much anyway?

Yes. It was very common a few decades ago in most HiFi
mags. Have a look at
Hi Fi News or similar back in the 1960s/1970s for example.

I think Stereophile still have some squarewave tests. IIRC
I've seen them
in issues in the last year or two. But they have
essentially vanished from
UK magazines.

A square wave test result seems to me
several levels of abstraction distant from what the
average audio
enthusiast might be interested in. It offered a
convenient method of
testing amplifiers for designers or home builders with
limited
equipment. It was never ideal because it superimposes
several tests
such that results need careful interpretive
disentanglement.

I agree.

When did it become common for 'scopes to have memory?
Perhaps it then
became unnecessary for the pulse to be repetitive.

IIRC I started using storage scopes back in the 1970s, and
also had
waveforms with pulsed/burst patterns with long gaps, etc.
But that was for
other kinds of work. I don't think that was common for
things like audio
mag reviews at the time.

But did they become so? What do mags use now instead? It
does seem that storage 'scopes were becoming common around
the time that square wave tests began to wane. Storks and
babies, maybe, not directly related but both linked to a
common theme. Hands-on engineering experience became less
common as machines became more complicated. Consequently,
interest in abstract technical tests was becoming less
common just as the capabilities of the test equipment was
rising. The classic story of alienation, I suppose. People
want nice pictures. Most of all, they want spectacular
destruction testing in exotic locations.

Don't you find it soul-destroying writing for HFN?

Ian

New page on Squares waves and amplifier performance
 

"Brian Gaff" wrote in message
om...
We used to use squarewaves for the following.
To show how bad tape machines were...
To show the tone control effects

However, you need to look at the harmonics on a true square wave, which of
course cannot actually exist.

**If you REALLY want to laugh, look at a 7kHz square wave from a CD player
(even 5kHz is barely passable from most CD players). A good R-R or high end
vinyl playback can do a MUCH better job.


--
Trevor Wilson
www.rageaudio.com.au

New page on Squares waves and amplifier performance
 

"Trevor Wilson" wrote in message
...

"Brian Gaff" wrote in message
om...
We used to use squarewaves for the following.
To show how bad tape machines were...
To show the tone control effects

However, you need to look at the harmonics on a true square wave, which
of course cannot actually exist.

**If you REALLY want to laugh, look at a 7kHz square wave from a CD player
(even 5kHz is barely passable from most CD players). A good R-R or high
end vinyl playback can do a MUCH better job.

Bull****

David.

New page on Squares waves and amplifier performance
 

Jim Lesurf wrote:
In article ,
bcoombes
bcoombes@orangedotnet wrote:
Ian Iveson wrote:
Jim Lesurf wrote:

I've just put up a new web page at

http://www.audiomisc.co.uk/HFN/Squar...quareDeal.html

that looks at the use of squarewaves for assessing amplifiers, etc.
You conclude that reviewers have abandoned the square wave, but did
they ever use it much anyway?

Without in anyway claiming to be an expert on these things I vaguely
seem to remember that most amp tests in the HI-Fi mags of the 1970's
and 80's had a square wave read out printed somewhere in the test. I
also *seem* to remember these were at 1k ...but of course these are
distant and increasingly dim memories. :)

I can confirm they did. Partly because I have a bookcase full of old issues
of HFN just beside me as I type. Also because I was working on developing
power amps at the time 'TIM' appeared on the scene and there was a brief
flurry of panic until people realised it was a 'problem' that decent design
solved with trivial ease.

Ah yes bit's all coming back to me now, there were a bunch of us at work who
were 'into hi-fi' and we'd spend much time studying the slew rate figures from
various amp tests and then deciding which one we'd like to own. ISTR that
Radford amps were the ones to die for back then.

New page on Squares waves and amplifier performance
 

David Looser wrote:
"Trevor Wilson" wrote in message
...

"Brian Gaff" wrote in message
om...
We used to use squarewaves for the following.
To show how bad tape machines were...
To show the tone control effects

However, you need to look at the harmonics on a true square wave,
which of course cannot actually exist.

**If you REALLY want to laugh, look at a 7kHz square wave from a CD
player (even 5kHz is barely passable from most CD players). A good
R-R or high end vinyl playback can do a MUCH better job.

Bull****

**Red Book CD tops out at 22.05kHz. A decent RR can easily top 30kHz. A top
of the line vinyl rig can easily manage 60kHz. Do the math.


--
Trevor Wilson
www.rageaudio.com.au

New page on Squares waves and amplifier performance
 

"Brian Gaff"


Tape, as I said in another response here had problems as it was obviously
impossible to record DC to a tape, so the flat tops were not flat.

** Huh ???????

Response down to DC is not a requirement for flat topped square waves !!!!

Square waves are NOT " little bits of DC " as fools like YOU think !!!!


You did not cover this aspect,


** Good thing he did not - since it would have been total ********.

For god's sake, learn some electronics - you damn fool.



..... Phil

New page on Squares waves and amplifier performance
 

"Trevor Wilson"

**If you REALLY want to laugh, look at a 7kHz square wave from a CD player
(even 5kHz is barely passable from most CD players). A good R-R or high
end vinyl playback can do a MUCH better job.


** Square waves output from a CD player (with a suitable test disk) are near
perfect examples of audio band limited square waves. The amplitude and
frequency are steady as a rock, harmonic phase relationships are near
perfect, channel matching is perfect and only inaudible harmonics are
missing.

OTOH, the square wave performance of typical hi-fi R-R and cassette decks is
utterly woeful. Amplitude is modulated all over the place, there is wow and
flutter, channel matching is woeful, there is obvious tape noise, harmonic
phase relationships are all out of wack, there is obvious ringing and still
the inaudible harmonics are missing.

In the cases of both LP and cassette, it is only possible to record a square
wave with low amplitude ( ie -20 dB or so) with any hope of just getting the
available bandwidth.

With CD, it makes no difference - full level ( ie 0dB) square waves are
routine.

TW is bereft of even a single clue.



..... Phil

New page on Squares waves and amplifier performance
 

Jim Lesurf wrote:
Hi,

I've just put up a new web page at

http://www.audiomisc.co.uk/HFN/Squar...quareDeal.html

that looks at the use of squarewaves for assessing amplifiers, etc.

During a tidy up I found a 6 page article on "Square Wave Testing of Audio
Amplifiers" in the NZ publication - Radio & Electrical Review - of August
1955. In it, it goes on to describe the testing of amplifiers using square
waves as a relatively new process. :)

And just to show that that the more things change the more they stay the
same, the article also says - and I quote "Now when we have a number of
amplifiers whose specifications, as outlined , indicate such excellent
performance, one might legitimately expect, when listening tests are
conducted, using identical programme material, and the same pick-up and
speaker system, that all the amplifiers sound the same. It was with
considerable surprise that we found exactly the opposite. "

They did tests on 7 un-named amplifiers and included oscillograms of the
amplifiers at 30hz, 400hz & 10,000hz.

The conclusion reached was that square wave testing "can help sort the
sheep from the goats. With all its advantages, this type of test will still
not give an unambiguous answer to the 40 dollar question ...Will this
amplifier sound well on music?. It will give the experienced worker a
pretty good idea of where his designs could be improved, and it seems that
the very best amplifiers do give very similar square wave results. Where
faults are apparent, the test shows them up much more clearly than any
other method, and will also indicate fault conditions that cannot readily
be discovered at all in any other way."

So here we are, 55 years down the track and its deja vu all over again :0

Mike

New page on Squares waves and amplifier performance
 

"Trevor Wilson" wrote


**Red Book CD tops out at 22.05kHz. A decent RR can easily top 30kHz. A
top of the line vinyl rig can easily manage 60kHz. Do the math.


And what do your ears top-out at?

David.