[LAU] Pro Audio? OT rant.

[Florian Paul Schmidt]

On 12/29/2012 01:47 AM, Jörn Nettingsmeier wrote:
> On 12/28/2012 03:50 PM, Chris Bannister wrote:
>>
>> I am referring to the faithfulness of the reproduction, when
>> comparing analogue to digital. On paper, an analogue signal is an exact
>> reproduction whereas a digital signal is, by its very nature, an
>> approximation of the original, even if it is very close.
>
> chris, i love my vinyls, but this argument is as old and tired as it 
> is wrong. any medium this side of the river jordan is band-limited, no 
> matter whether it's analog or digital.

This is true. And not also is it bandlimited, but also introduces 
non-linearities

>
> the evil little steps in a digital pcm stream are just an upper band 
> limit, and they are _low-pass_filtered_ on playback, which makes them 
> into a time- and value-continuous signal, i.e. analog.
>
> if you think your lps give you some ultrasonic revelations, measure 
> again, and again after playing them ten more times. if the magic were 
> in the octave from 20-40khz, then every lp would be a disposable "use 
> once" medium. the frequencies below that are reproduced _perfectly_ by 
> a cd.

Playing the devil's advocate here..

Not true. There's also quantization error due to each sample being 
represented as a discrete value from a set of 2^16 values in the case of 
a CD. Shannon's sampling theorem requires afaict that the samples are 
from the set of the real numbers.

http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem

http://en.wikipedia.org/wiki/Quantization_error

[...]

What makes digital systems so attractive is that both the bandwidth and 
quantization error are easier to control than the typical limitations a 
purely analogue system has. If your system has too little bandwidth then 
increase the sampling frequency. If it has too much quantization noise, 
increase the bit depth. A vinyl record and a physical record player have 
so many hard to control limitations that it's just cheaper (much 
cheaper) to get a sufficiently good reconstruction ability with a 
digital system.. Needles have mass, they are non-rigid, the vinyl is 
elastic, the speed of light is finite, etc. pp.. In the end a digital 
playback system needs a D/A which is again an analogue system. But still 
it's cheaper to get it good enough (testably) with a digital system and 
a quality D/A than a purely analogue chain.

Have fun,
Flo



-- 
Florian Paul Schmidt
http://fps.io