[LAU] 24-bit files and hisss.... GOT IT

Sampo Savolainen v2 at iki.fi
Mon Feb 16 13:49:50 EST 2009

On Mon, 2009-02-16 at 10:50 -0700, Bearcat M. Şandor wrote:
> ok, so i'm confused.  If you're saying that upsampling is generally a bad 

Say you have a CD with nothing but 74 minutes of "perfect" 440Hz sine
wave. As CDs are, the data is at 44.1k, which means that it can contain
only frequencies below 44.1k/2 (< 22050Hz). If you upsample this sine
wave to 96k, you will have 96k PCM data that contains a "perfect" sine
wave at 440Hz. You've added nothing to the signal so nothing has

.. except for the fact that the sample rate conversion will cause
distortion, noise and phase issues. There are really good algorithms
(libsamplerate) or obscenely good ones (check out izotope's scores on
http://src.infinitewave.ca/ ). But nevertheless none of them are perfect
and none of them cad add more "sound" to the original.

You can expand this naive example to any sound contained on a CD. The CD
will always contain only frequencies below 22050Hz, any upsampled
version will only have frequencies below 22050Hz however high of a
sample rate you choose. Except for the distortion caused by the
algorithm which will contain frequencies above 22050Hz.

> thing why does one pay extra for it in  a product like this: 
> http://www.meridian.co.uk/product-model/g-series/g082-upsampling-compact-disc-
> player.aspx ?

Good marketing?

I find it hard to believe that upsampling PCM data does anything that a
proper DAC doesn't. Many DACs use techniques to give the same benefits
what the meridian web page describes as the benefit of upsampling:
"filtering to take place far beyond the range of human hearing". People
who know more about DACs can pitch in and provide more precise
information if needed.

Let's ask the question the other way around: if upsampling is a superior
way to convert from digital to analog, why do we see upsampling being
mentioned only in obscenely expensive hi-fi CD players? Why Lynx,
Apogee, RME, etc. don't use this technology in their highly praised


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