The Well-Tempered Computer, an introduction to computer audio

Wednesday, November 16, 2011

Highres recordings

CD quality is 16 bit / 44.1 kHz sample rate.
Today you can buy 24 bit / 192 kHz recordings.
 Can your gear resolve this?


Let’s do some calculations (always tricky in my case)

Playing 192 kHz is 1/192.000 sample per second= 0.000005208333333333330 s
If the clock driving the DAC has an intrinsic jitter of 10 nano seconds then time step produced at DA conversion fluctuates between:
0.00000001 = 10 ns
0.000005218333333333330 +10 ns
0.000005208333333333330
0.000005198333333333330 -10 ns

Obvious the fluctuations in clock speed are pretty close to the time step.
Ok, let’s use a better clock, one with an intrinsic jitter of 1 pico second.

0.000000000001 = 1 ps
0.000005208334333333330 +1 ps
0.000005208333333333330
0.000005208332333333330 -1ps

In this case the variations in the time step look more decent.
The higher the sample rate the more import low jitter values become.
Of course jitter performance is far more complex but it looks like even a clock with an extreme low intrinsic jitter of 1 ps is not able to generate the correct time step.
So our gear can’t play 192 kHz with the right timing!

A bit more: http://www.whatsbestforum.com/showthread.php?4402-Timing-is-everything