Date:         Sun, 7 Jan 2007 01:08:09 -0600
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         phillip holmes <[log in to unmask]>
Subject:      square waves....Re: [ARSCLIST] Libraries disposing of records
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A square wave on a record doesn't look like a square because of the 
velocity involved--or something--that I can't explain.  A square wave is 
built up of stacked "odd integer harmonics" and contains multiple 
harmonics.  Somewhere around 12 harmonics, it really looks like a square 
wave.  The more harmonics present, the more perfectly formed the square 
wave becomes.  A perfect square wave would require infinite bandwidth 
and infinitely fast electronics (forget the stylus, we can't even 
generate a perfect square wave, only a mathematical representation of 
one).  What it looks like on record is fundamentally different from what 
a scope shows.  There's no co correlation.  Somewhere I have an email 
from Stan Ricker about it.  If I can find it, I'll send it along.
Phillip

Mike Richter wrote:
> Steven C. Barr(x) wrote:
>> ----- Original Message ----- From: "Scott Phillips" 
>> <[log in to unmask]>
>>> Use sound forge or similar and look at a remastered LP at the least, or
>>> a current recording... The results are a LOT of square waves<snip>
>>>
>> Would it be possible/practical to record a signal containing "square
>> waves" (or approximately such)? Can an analog stylus make such an
>> abrupt right/left turn?
>
> Yes on both counts - but with caveats.
>
> 1. The signal will not be captured perfectly. One needs to define how 
> accurate a capture qualifies as success.
>
> 2. The higher the frequency, the lower the accuracy of capture. The 
> higher the amplitude, the more likely that artifacts will be detected.
>
> 3. The detector (stylus, cartridge and preamp) are sources of 
> imprecision in matching input to output.
>
> NOTE: Ringing can be eliminated by rolling off the highs - another 
> source of inaccuracy.
>
> Mike