[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Date Index][Thread Index][Author Index]

Re: sample rate

im not arguing with u. and im not going to try to prove anything to u based
on my background knowledge, which u know nothing of.
but let me say this, u r also a victim of ur arrogance.

just suppose, just suppose that the high freq ur trying to reproduce is NOT
a sine wave but u still only have 2 points (a sawtooth wave), what then??
a sine wave??

what was the argument about? to prove ME wrong or to discuss the limits of
u sound to me like the guy that would bring up last months argument when u
find urself at the losing end of todays with ur wife.

----- Original Message ----- 
From: "Bill Fox" <billyfox@soundscapes.us>
To: <Loopers-Delight@loopers-delight.com>
Sent: Sunday, December 25, 2005 12:29 PM
Subject: Re: sample rate

> Adrian Bartholomew wrote:
> > this is where SOME info is worse than NO info.
> > dude think about it.
> > u have a wave at 1/2 the sample frequency. think about it like
> > connect-the-dots.
> > the only ones u can plot are the max(positive) and min(negative)
> > points of the wave. NOW connect the dots and what do u have. thats
> > right a sawtooth wave. even if the original was a sine.
> > but at least u have the frequency. forget about phase what about shape
> > or tone?
> > even if u sampled at a frequency high enough to give u three or even 4
> > points to connect, its STILL approximate, very far from the shape of
> > the original and certainly not "all the information of the original
> > signal".
> Dude, there is no connect the dots in a sampled system.  Electronically,
> the dots AREN'T connected.  The DAC outputs a stepped series of voltages
> that feed a reconstruction filter, i.e. an LPF.  This filter takes your
> so-called sawtooth, filters out everything above the LPF's pernamently
> set cutoff frequency and voila, you get a sine wave!  Think about it a
> minute.  The LPF is set to filter out everything above (0.5)fs, where fs
> is the sampling frequency.  fs is the first possible overtone of ANY
> waveform that isn't a sine.  What you think is a sawtooth is actually a
> square wave.  But you won't hear anything except the original sine wave
> being reconstructed.
> The lack of information or understanding is yours.  I can't give you the
> engineering background required to prove that I'm right.  You'll have to
> spend a few years first, learning higher mathematics andinformation
> theory.  But every CD player, every DVD player, every minidisc, DAT, and
> iPod prove me right.
> Cheers,
> Bill