Yamaha CBX-D5 - Manual (Page 26)

20 Chapter 7 : Recording 20 Chapter 7 : Recording 20 Chapter 7 : Recording
7 Recording
Sampling frequency (REC FREQ)
The CBX-D5 can record at any one of four sampling frequencies: 48kHz, 44.1kHz, 32kHz
(as specified by the AES), or 22.05kHz (analog input only). These sampling frequencies
are commonly used for digital audio, and each has its own specific applications.
The sampling frequency is set by the controlling software and the CBX-D5’s front panel
REC FREQ indicators show the selected frequency. The selected REC FREQ also
determines the clock rate for all internal processing, i.e., DSP, digital mixer, DEQ, etc.,
except for the output Fs converters, whose clock rate is determined by the PB FREQ.
48kHz
At 48kHz an audio bandwidth of about 22kHz is possible. Consumer DAT and DCC
recorders can record at 48kHz only. Professional equipment also supports this frequency.
44.1kHz
With this sampling frequency an audio bandwidth of about 20kHz is possible. This
frequency is used for all prerecorded CDs, DATs (if there are any), and DCC cassettes.
Although a higher audio bandwidth is possible using 48kHz, 44.1kHz is considered to be
good enough for most applications, and most professional digital audio engineers use this
sampling frequency.
32kHz
At this sampling frequency an audio bandwidth of about 15kHz is possible. This frequency
is widely used for broadcast applications where a 15kHz audio bandwidth, roughly that of
FM radio, is acceptable. Many DSB (Direct Satellite Broadcasting) transmissions use this
frequency, although, some may also use 48kHz.
22.05kHz
At this frequency an audio bandwidth of about 10kHz is available. This frequency is
widely used in multimedia applications. It might not seem very useful for your audio
applications, but if you are limited by hard disk space or the audio material you are
recording already has a limited bandwidth it may be useful.
Which sampling frequency?
Since the CBX-D5 contains a sampling frequency converter, digital audio can be output at
a different sampling frequency to that which was used during recording. However, playing
back a sound file at a higher sampling frequency will not improve the audio quality, as the
audio frequency bandwidth of a sound file is determined by the record sampling frequency,
not the playback frequency.
This leaves you with two deciding factors for choosing a sampling frequency. Firstly, what
audio bandwidth (audio quality) do you want to use, and secondly, how much free disk
space is available? See “Hard disk size” on page 13 for a listing of recording times that are
available at each sampling frequency for a given size of hard disk (free disk space).
Varispeed
With some tape based digital recorders it is possible to vary the speed of playback and
recording. When varispeed is used the sampling frequency of the digital audio is changed.
Since the CBX-D5 can playback digital audio at a sampling frequency different to that
used for recording, varispeed digital audio can be recorded.
NOTE: When using the digital inputs, you should set the CBX-D5’s REC FREQ to
match the digital input signal’s sampling frequency. It is not essential, but we
recommend it.