Tascam DA-78HR - Manual (Page 44)

7 - Advanced operations
TASCAM DA-78HR
44
(for instance 16, the DA-78HR’s non-HR tape word
length) to improve quantization.
Paradoxically, this technique of adding noise
removes quantization noise and distortion at low sig-
nal levels and improves the overall distortion fig-
ures.
1
Though quantization noise is reduced, there is a loss
of a few dB in the signal-to-noise ratio. For this rea-
son, the DA-78HR does not implement dither as a
standard, but allows you to choose between no dither,
rectangular or triangular (the shapes refer to the dis-
tribution of values in the digital noise). Rectangular
gives about 3dB better signal-to-noise ratio than tri-
angular, but there is noise modulation, which may be
audible when recording and playing back low-level
program sources.
NOTE
Dither can be turned on and off while recording is
taking place. However, there will probably be an audi-
ble change in the sound quality. We suggest making
a test recording before a session. In this way you will
be able to make an instant assessment of the effects
of the different dither settings on your program mate-
rial.
7.11.1 Selecting dither settings
1 Press the SHIFT key so that the SHIFT indicator
is flashing, and then press the MENU key until
the display shows Audio. 1-- ( AUDIO1-- ).
2 Press the SUB MENU key until the display
shows
DITH. ;;;
( DITH xxx where xxx is the
current setting).
3 Use the ▲ and ▼ to select the dither function
you want (either
OFF (
OFF ),
RECT (
RECT )
(rectangular) or
TRI (
TRI ) (triangular)).
7.12Advanced output options
7.12.1 Output word length
The output word length from the TDIF-1 (and the
SPDIF ( COAXIAL )) outputs can be set to either 16 or
24 bits.
1 Press the SHIFT key so that the unit is in shift
mode ( SHIFT indicator is flashing).
2 Press the MENU key until the display shows
Audio. 2-- ( AUDIO2-- ).
3 Press the SUB MENU key until the display
briefly shows Out. bit. ;; ( OUT BIT xx) ,
where xx is the current setting.
4 Use the ▲ and ▼ keys to change between 16
and 24 bits.
NOTE
Simply changing the output word length to 24 bits will
not automatically provide better sound quality, if the
equipment being fed by the DA-78HR is not capable
of accepting 24-bit audio.
7.12.2 Output patchbay
In addition to the integral input patchbay, the DA-
78HR also features a patchbay which allows tracks to
be routed to different output channels.
This routing is carried out in parallel to both the
TDIF digital and the analog sets of outputs.
The default setting is NORMAL ( NORMAL ), i.e.
tracks are output to their correspondingly-numbered
output channels.
To make an output patch setting:
1 Press the SHIFT key so that the unit is in shift
mode ( SHIFT indicator is flashing).
2 Press the MENU key until the display shows
Audio. 2--
( AUDIO2-- ).
3 Press the SUB MENU key until the display
briefly shows Out. Patch ( OUT PATCH ), fol-
lowed by the current setting.
4 Press any of the REC FUNCTION keys to select
an output channel (not a track) which will have
a track assigned to it.
5 The display shows the current setting of this
output channel, e.g.
Ch. 1 Tr. 3 ( Ch1 tr3 )
means that output channel 1 is fed by tape
track 3. Use the ▲ and ▼ keys to change the
track number.
1. A full discussion of dither and other digital
audio techniques is outside the scope of this
manual. However, a good starting point for
learning about this, and other aspects of digital
audio, is John Watkinson’s The Art of Digital
Audio, pub Focal Press.