360 Systems DigiCart/EX User Manual
Page 52
40
• 28BRecording
WAV or DigiCart format, 24-bit recordings are WAV file format. DigiCart/EX cannot perform internal
data format conversions. Recordings must pass through the I/O connectors to be converted.
It is sometimes desirable to output a smaller digital word size for use by external equipment, such as
a 16-bit DAT recorder. The OUTPUT WORD SIZE selection in the Setup menu gives you two
choices: 24-BITS (no dithering
), or 16-BITS (8-bit dithering.)
The following tables list record and play format options, menu settings, and front panel indicators:
Record Modes
Input Data
Format
Recorde
d Format Setup Menu
Format
Indicator
Dithered
Indicator
24
24
SETUP | Record Data Format = 24-Bit
24
OFF
24 16
SETUP | Record Data Format = 16-Bit
Dithered
16 ON
16
24
SETUP | Record Data Format = 24-Bit
24
OFF
16
16
SETUP | Record Data Format = 16-Bit
16
OFF
The RECORD DATA FORMAT parameter in the Setup menu specifies both the sample size (16 or 24
bits) and the file format (DigiCart, WAV, or compressed as AC-2) to be used for recordings.
The RECORD DITHERING setup parameter is used to tell the machine that 24-bit digital data is
being supplied to the digital inputs with the intention of making a 16-bit recording. If the RECORD
DATA FORMAT parameter is set to 16-BIT, then the 24-bit incoming audio is dithered down to 16-
bits during the recording, illuminating the Dithered indicator on the front panel.
Play Modes
Recorded
Data
Format
Output
Data
Format
Setup Menu
Format
Indicator
Dithered
Indicator
24
24
SETUP | Play Word Size = 24-Bit
24 OFF
24
16
SETUP | Play Word Size = 16-Bit
16
ON
16
16
SETUP | Play Word Size = 16-Bit
16
OFF
The PLAY WORD SIZE parameter in the Setup menu specifies the sample size (16 or 24-bits) at the
digital output connectors. If the selection is set to 16-BIT and a 24-bit cut is being played, then the
sample size is dithered down to 16-bits, illuminating the Dithered indicator on the front panel.
*
Truncating 24-bit samples to 16-bits can result in signal distortion, especially noticeable at low levels.
Dithering is a technique of adding appropriate random data to the 24-bit digital output stream before reducing
the word size. This results in a very low-level broadband noise being added to the signal, rather than the more
objectionable signal distortion. DigiCart/EX dither uses a zero-mean random noise source with a triangular
probability distribution. Its peak level corresponds to the magnitude of the least significant bit of the reduced
word size within the 24-bit field. The method is called “LSB TPDF dither” for Least Significant Bit Triangular
Probability Density Function.