User's Manual

Digital Belt-Pack Transmitter
Rio Rancho, NM
3
DBu, DBu/E01 Block Diagram
Filters
Keypad
(2) AA
Batteries
Oscillator
VCTXO
I2S
I2S
Voltage Controlled
Oscillator
Final
Amplifier
Control
PLL Ref
Phase Locked Loop
DSP Clock
Switching
Power
Supply
Microprocessor
Power
LED
Tr icolor
D-A Convert-
er
A-D
Converter
Shunt
Limiter
Limiter Control
Gain
Adj
HI/Lo
Pass
Filter
Input
Preamp
Input
Jack
Bias Voltage
0, 2 or 4V
Servo Bias
Supply
+5V
I + Q
Baseband
Signals
Low
pass
filters
IQ Modulator
UART
USB
Jack
Security Key
Audio
Firmware
Update
Key Received
Blue LED
Low
Pass
Filter
Buffer
36.864 mHz
IR Port
DBu Transmitter
Consumer Alert for US Users - FCC Order DA 10-92
Most users do not need a license to operate this wireless microphone system. Nevertheless, operating this microphone system
without a license is subject to certain restrictions: the system may not cause harmful interference; it must operate at a low power
level (not in excess of 50 milliwatts); and it has no protection from interference received from any other device. Purchasers
should also be aware that the FCC is currently evaluating use of wireless microphone systems, and these rules are subject to
change. For more information, call the FCC at 1-888- CALL-FCC (TTY: 1-888-TELL-FCC) or visit the FCC’s wireless microphone
website at www.fcc.gov/cgb/wirelessmicrophones. To operate wireless microphone systems at power greater than 50mW, you
must qualify as a Part 74 user and be licensed. If you qualify and wish to apply for a license go to: http://www.fcc.gov/Forms/
Form601/601.html
Servo Bias Input and Wiring
The DBu, DBu/E01 input preamp is a unique design
that delivers audible improvements over conventional
transmitter inputs, is easier to use and much harder to
overload. It is not necessary to introduce pads on some
mics to prevent overload of the input stage, divide the
bias voltage down for some low voltage mics, or reduce
the limiter range at minimum gain settings.
Two different microphone wiring schemes are available
to simplify and standardize the configuration. Simpli-
fied 2-wire and 3-wire configurations provide several
arrangements designed for use only with servo bias
inputs to take full advantage of the preamp circuitry.
Other wiring schemes are compatible with Servo Bias
and conventional inputs.
A line level input wiring provides an extended frequency
response with an LF roll-off at 35 Hz for use with instru-
ments and line level signal sources.
DSP-controlled Input Limiter
The transmitter employs a digitally-controlled analog
audio limiter prior to the analog-to-digital converter.
The limiter has a range greater than 30 dB for excellent
overload protection. A dual release envelope makes the
limiter acoustically transparent while maintaining low
distortion. It can be thought of as two limiters in series,
connected as a fast attack and release limiter followed
by a slow attack and release limiter. The limiter recovers
quickly from brief transients, so that its action is hidden
from the listener, but recovers slowly from sustained
high levels to keep audio distortion low and preserve
short term dynamic changes in the audio.