[Meindert Sprang]

"Jim Lesurf" wrote in message
...
I've now done this and the results can be seen at

http://www.audiomisc.co.uk/HFN/OTTre...d/results.html

My thanks to Keith Howard for kindly agreeing to let me publish his
measured results. Note they were made in 2007 so only covered the players
and DACs he had to hand at that time. But - rather depressingly - all but
one of the nine he tried showed they had problems coping with the waveform
that has peaks at +3dBFS.

FWIW personally I'd love to see all reviews on DACs or player use the
'waveform from hell' I devised for the original article (a link to that is
on the above page) as a test of how they cope - or not! :-) I have the
uncomfortable feeling that whilst reviews continue to overlook this area,
problems will continue to afflict some new designs without anyone knowing.

This test is flawed. The sample points on the right represent a sinewave of
+3dBFS. If you would sample a sinewave on the tops, you would indeed get the
picture as shown on the left. If you move the sample points to the positions
as shown in the picture on the right, the sample points would be 3dB down
and they would still represent a sinewave of 0dBFS.

Following this reasoning, one could say that if a DAW normalizes by simply
measuring the highest sample and scaling all others accordingly, that DAW is
flawed too. It should at least "reconstruct" the whole waveform to be able
to determine the *real* maximum amplitude.

So the question is: do we know how a DAW measures the maximum amplitude? Is
it documented in the manual/specs? If not, using -3dBFS is always safe
because this is the worst case we could encounter as seen in the test.

In reality, a piece of audio with thousands of samples would probably have a
few that are nearly on the top of a loudest sinewave, statistically
speaking, so -1dBFS would *probably* do as well as someone else already
mentioned.

Interesting stuff when you think about it....

Meindert