"Dick Pierce" wrote in message
...
Audio Empire wrote:
24 KHz is possible with DAT (48KHz sampling rate)
No, it is not. First, the Nyquist criteria requires
the bandwidth to be limited to less than half the
sample rate, not less than or equal to half. Second,
the transition bandwidth is not infinitesimal.
practically speaking, most DAT recorders had bandwidth
similar to CD players.
Except that CD players have a maximum sampling frequency of 44.1 KHz which
is set by the Red Book standard.
Let's not split hairs. while it is true that a 48 KHz digital signal can't
reproduce 24.000 KHz, it can reproduce 23 Khz, 23.5 kHZ, and in many cases
23.9 KHz. It depends, but many DACs don't have low pass filters that even
come close to totally obliterating the signal at 0.95 Nyquist, or at even
at the Nyquist frequency.
For example, the well-known Analog devices AD 1853 DAC
http://www.analog.com/static/importe...ets/AD1853.pdf
spec sheet says that its stop band is 26.23-358.28 KHz. 26 KHz is Nyquist +
2 KHz! According to Figure 14, its digital filter is only about 10 dB
down at 50 KHz with a 96 KHz clock. This is equivalent to being 10 dB down
at 24 KHz with a 48 KHz clock.