In article ,
"William Sommerwerck" wrote:

Get out your microscope and look at the grooves and compare
to the playback waveforms. Complex waveforms are ok but
something like a square wave groove would be best.

Do you know of a disk that has a square wave cut on it?
I have a lot of test disks, but I don't remember one. I'll have to look.

Think about what the stylus would have to do. That's why you won't find
a test disk with a square-wave groove on it.

I assume you mean the cutting stylus.

No; I mean the playback stylus. In the groove, the rising and falling
edges of the waveform would be perfectly perpendicular to the motion of
the disk, and so there would be no possible way for the stylus to follow
it. And if they were not perpendicular, then it wouldn't be a square
wave.

It is possible to send a signal to a
cutting head that would, in principle, produce a square wave on the blank.
For example, you could cut a 200Hz square wave with 36dB of pre-emphasis at
12.8kHz, which is not unreasonable.

That still would not be truly a "square" wave, because the rise and fall
times would not be infinitely fast. You could do it by stopping the
rotation of the disk while the rising and falling edges were being cut,
for example, but no matter; the groove still could not be tracked by a
mechanical stylus.

Isaac