1-2

1.2 Specifications
Layout:
Rack-mount unit incorporating a
professional surround decoder module,
interface circuitry, and power supply.
Signal Connections: (on rear panel)
Lt (Left Total) and Rt (Right Total) XLR
inputs for two-channel encoded signal; Left,
Center, Right, and Surround XLR outputs.
Additionally, Lt, Rt, and Left, Center, Right,
and Surround monitor points are provided
at a 25 pin female D connector.
Front Panel Controls and Indicators:
One toggle switch and three push-button
switches control system operating modes
and internal test signals. A single rotary
knob controls four-channel master level.
Screwdriver adjustable controls recessed
behind panel for adjustment of input and
output levels. LED meters indicate Lt and Rt
input level. Signal present LEDs indicate
Left, Center, Right, and Surround decoder
outputs.
Input Circuit: (0 dBr=0.775 V rms)
Two balanced floating transformerless
inputs. Input gain adjustment will
accommodate a range of 300 mV (–8.2 dBr)
to 2 V rms (+8.2 dBr). Input impedance is
greater than 10 k ohms. Maximum common
mode voltage 4 V rms, 5.8 V peak.
Output Circuit:
Four balanced floating transformerless
outputs. Output gain adjustment will
accommodate a range of 250 mV (–9.8 dBr)
to 2.5 V (+10.2dBr) at the normal master
level control setting. Output impedance 25
ohms.
Maximum output voltage +26 dBr into
balanced 600 ohm load, less into lower
impedances. Maximum output +20dBr into
unbalanced 600 ohm load.
Operating Modes:
Dolby Surround, conventional stereo, and mono
modes, selected by front panel pushbutton
or remote control.
Pink Noise Calibration Function:
Pink noise from the SDU4’s internal
generator can be sent to the outputs in several
ways. Noise can be automatically cycled
between Left, Center, Right, Surround,
remaining for 3 seconds at each output (LCRS
sequence); or cycled between Center and
Surround remaining for 3 seconds per output
(CSCS sequence); or to any desired channel
under manual control. The system should
be adjusted so this signal produces a sound
pressure level (SPL) of 85dBc at the desired
monitoring position.
Center Speaker In/Out:
Selected by an internal switch. Used to match
either theater-style systems with three front
channels or smaller systems with two front
loudspeakers. The latter mode routes
spatially decoded signals from the surround
decoder as follows: left decoder output to
Left main output; right decoder output to
Right main output; center decoder output
split to Left and Right main outputs at a
reduced level; surround decoder output to
Surround main output.
Monitor Outputs:
Single-ended monitor outputs are provided
for Lt and Rt and for L, C, R, and S signals.
Dolby level is 500mV (–3.8dBr) at these
outputs. Output impedance is 200 ohms or
less, and these outputs can drive loads greater
than 10 k ohms.
Overall Frequency Response:
20Hz-20 kHz ± l dB (L, C, and R)
100Hz-7 kHz ± 3 dB (surround output)
S/N Ratio: (referenced to Dolby level)
Greater than 80 dB (Left, Center, Right),
CCIR/ARM weighted.
Greater than 70dB (Surround), CCIR/ARM
weighted.
(Master level control at normal setting.)
Distortion:
Total Harmonic Distortion (THD) at the main
balanced outputs will not exceed 0.25% into
balanced loads 600 ohms or greater at any
output level up to 12.5 V rms at any master
level control setting.
THD at Dolby level at 1kHz with input and
output adjusted for +4dBr, 0.1% typical.
Ambient Operating Temperature:
Up to 40 degrees C.
Finish:
Bottom tray and cover clear alodine. Front
panel black with white lettering.
Size:
1 Rack Unit 43 mm (1.75") high, 260 mm
(10.25") deep behind mounting surface;
maximum projection in front of mounting
surface 22 mm (0.875").
Weight:
5 kg (11 lb.).
Power Requirements:
The SDU4 consumes about 20 watts and is
designed for operation from a centrally
switched power source. 230 V version: 198-
264 V ac, 50/60 Hz, uses one 20 mm T250 mA
fuse. Multi-voltage version: 85-132 V ac,
50/60 Hz, uses one 1.25" 500 mA slow-blow
fuse, or 187-264 V ac, 50/60 Hz, uses one
20mm T250 mA fuse.
Specifications subject to change without
notice.
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