All very tuue. I suspect the design of the pulse itself will be next on the
agenda then. If a pulse of no rise or fall time could be made presumably it
would be silence if it had nil dwell time as well? grin.

One needs to design one shot and multi shot tests to allow the scope to see
what is going on, as listening to pulses all the time is hardly any kind of
way to go!

In any case, do you use plus only, or plus and minus pulses?
I seem to recall one weird amp from Sinclair I saw which had apparently
perfect results, but sounded absolutely terrible and radiated RF like a
power line adaptor, but you know what he was like!

The idea I think was to fast switch the output and use the duty cycle to
create the output, so small devices could be used. Trouble was that this
needed massive amounts of low pass filtering to get it to really work..
Ho hum.

Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Ian Iveson" wrote in message
...
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? 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.

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

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

With a single pulse and a 'scope with memory to capture its consequences,
the entire transient response, HF and LF, can be seen, without
interruption by successive pulses.

Ian