HI,
a long time ago, I read an article (or maybe it was
an ad) saying that atrac was superior to pcm when
recording analog source.
was it just sony propaganda or could there be some truth in this?

Beauty is in the eye of the Beholder..and holds true for a listening experience..except of course its the ears instead! It is highly subjective and more of a personal perference..

As a footnote - be prepared for some ATRAC bashing...this forum is not very kind when it comes to ATRAC :-))

ATRAC is lossily compressed PCM.

All other things being equal, if the only difference is ATRAC compression, ATRAC cannot be better than PCM.

Maybe yes, if by PCM they meant for instance 8-bit at 22kHz... while compressing to ATRAC from a CD quality source...

I think their argument was something like this :
atrac allows to record analog signal more acurately because
it can use more data for what is important (giving more detail
in recorded audio) and discard
unuseful stuff. This would result in better quality than pcm
because pcm can't make the difference between what
is useful or not.

Amazing that someone has to spell it out again, but ATRAC (R.I.P.) uses less data, since it's a lossy compression. Therefore it cannot be more accurate than uncompressed audio. You fell for some serious marketing talk when you believe that discarding data leads to better quality.