In article , 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.

Prompted to do this by noticing squarewave results being used to
present ideas about speaker cables, and realising that the humble
squarewave has largely fallen into disuse.

I've also tweaked the site a bit, and hope to make a few other minor
improvements and alterations soon.

Slainte,

Jim


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.

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.

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.

Slainte,

Jim

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