Lectrosonics LMBC1 User Manual
LMb
Synthesized UHF Belt-Pack Transmitter
Featuring
Digital Hybrid Wireless
Technology
US Patent 7,225,135
INSTRUCTION MANUAL
®
Fill in for your records:
Serial Number:
Purchase Date:
Quick Start Steps
1) Install good batteries and turn power on (see pages
6 and 7).
2) Set compatibility mode to match the receiver (see
page 9).
3) Connect signal source and adjust input gain for
optimum modulation level (see page 9).
4) Set StepSize and frequency to match receiver (see
page 10). Also see receiver manual for scanning
procedure.
5) Turn on the receiver and verify RF and audio signals are present (see receiver manual).
Rio Rancho, NM, USA
www.lectrosonics.com
LMb
Table of Contents
Introduction .............................................................................3
About Digital Hybrid Wireless ...............................................3
Frequency Agility...................................................................3
Wide-Band Deviation ............................................................3
Servo Bias Input and Wiring .................................................3
LMb Block Diagram ...............................................................4
DSP-controlled Input Limiter ................................................. 4
No Pre-Emphasis/De-Emphasis ...........................................4
Pilot Tone Squelch ................................................................4
Battery Installation .................................................................5
Belt Clips ................................................................................. 5
Operating Instructions ........................................................... 6
Battery Status LED Indicators ............................................... 6
Powering On in Operating Mode ...........................................6
Powering On in Standby Mode .............................................7
Powering Off .........................................................................7
Navigating Menus .................................................................7
Locking/Unlocking Changes to Settings................................7
Power Menu .......................................................................... 7
Selecting Programmable Switch Functions...........................8
Main Window Indicators ........................................................8
IR (infrared) Sync .................................................................. 9
Selecting the Compatibility (Compat) Mode ..........................9
Connecting the Signal Source ..............................................9
Adjusting the Input Gain ........................................................9
Selecting Step Size ............................................................. 10
Selecting Frequency ...........................................................10
Selecting Frequency Using Two Buttons ............................. 10
Helpful Features on Receivers ............................................10
About Overlapping Frequency Blocks .................................11
Selecting Audio Polarity (Phase) ......................................... 11
Adjusting LCD Backlight .....................................................11
RF ON/OFF on the Menu ....................................................11
Selecting Battery Type ........................................................11
Restoring Default Settings ..................................................11
5-Pin Input Jack Wiring ........................................................ 12
Microphone Cable Termination
for Non-Lectrosonics Microphones .............................13
Input Jack Wiring for Different Sources ............................. 14
Compatible Wiring for Both Servo Bias Inputs
and Earlier Transmitters: .....................................................14
Simple Wiring - Can ONLY be used
with Servo Bias Inputs:........................................................14
Microphone RF Bypassing .................................................. 15
Line Level Signals ............................................................... 15
Wiring Diagram for MI39A Instrument Cable ......................15
Accessories ..........................................................................16
Troubleshooting ....................................................................17
Specifications and Features ................................................ 18
Service and Repair ...............................................................19
Returning Units for Repair ..................................................19
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
2
LECTROSONICS, INC.
Introduction
The design of the LMb transmitter delivers the advanced technology and features of Digital Hybrid Wire-
®
less
in a Lectrosonics belt-pack transmitter at a modest
cost. Digital Hybrid Wireless
audio chain with an analog FM radio link to eliminate a
compandor and its artifacts, yet preserve the extended
operating range and noise rejection of the finest analog
wireless systems. DSP “compatibility modes” allow the
LMb to also be used with a variety of analog receivers
by emulating the compandors found in earlier Lectrosonics analog wireless and IFB receivers, and certain
receivers from other manufacturers (contact the factory
for details).
The housing is a rugged, machined aluminum package
with removable, stainless steel wire belt clip. The input
jack is a standard Lectrosonics 5-pin type for use with
electret lavaliere mics, dynamic mics, musical instrument pickups and line level signals. The LEDs on the
top panel allow quick and accurate level settings without
having to view the receiver. The unit is powered by two
AA batteries. The antenna is a super-rugged, permanently attached 1/4 wavelength design made of flexible
galvanized steel cable.
The switching power supplies in the LMb provide constant voltages to the transmitter circuits from the beginning to the end of battery life, with output power remaining constant over the life of the battery. The input amplifier uses an ultra low noise op amp for quiet operation.
Input gain is adjustable over a 44 dB range, with a DSP
-controlled dual envelope input limiter to cleanly handle
signal peaks over 30 dB above full modulation.
About Digital Hybrid Wireless
All wireless links suffer from channel noise to some
degree, and all wireless microphone systems seek to
minimize the impact of that noise on the desired signal.
Conventional analog systems use compandors for
enhanced dynamic range, at the cost of subtle artifacts
(known as “pumping” and “breathing”). Wholly digital
systems defeat the noise by sending the audio information in digital form, at the cost of some combination of
power, bandwidth, operating range and resistance to
interference.
The Lectrosonics Digital Hybrid Wireless
comes channel noise in a dramatically new way, digitally
encoding the audio in the transmitter and decoding it
in the receiver, yet still sending the encoded information via an analog FM wireless link. This proprietary
algorithm is not a digital implementation of an analog
compandor but a technique which can be accomplished
only in the digital domain.
Since the RF link between transmitter and receiver is
FM, channel noise will increase gradually with increased operating range and weak signal conditions,
however, the Digital Hybrid Wireles system handles
this situation elegantly with rarely audible audio artifacts as the receiver approaches its squelch threshold.
In contrast, a purely digital system tends to drop the
®
combines a 24-bit digital
®
system over-
Digital Hybrid Wireless Belt-Pack Transmitter
audio suddenly during brief dropouts and weak signal
conditions. The Digital Hybrid Wireless
encodes the signal to use a noisy channel as efficiently
and robustly as possible, yielding audio performance
that rivals that of purely digital systems, without the
power, noise and bandwidth problems inherent in digital
transmission. Because it uses an analog FM link, Digital
Hybrid Wireless
FM wireless systems, such as excellent range, efficient
use of RF spectrum, and long battery life.
®
enjoys all the benefits of conventional
®
system simply
Frequency Agility
Frequency selection is provided in 100 kHz or 25 kHz
steps with up to 3072 channels available covering three
standard Lectrosonics 25.6 MHz blocks. Frequencies
are displayed on the LCD in MHz and in a hex code
used with earlier Lectrosonics equipment.
Wide-Band Deviation
Deviation has a direct effect on the dynamic range and
signal to noise ratio of an FM system. The greater the
deviation, the wider the dynamic range and the better
the signal to noise ratio. In the Digital Hybrid Wireless
mode, the system operates with a maximum of +/-75
kHz of deviation. The resulting 180 kHz of occupied
bandwidth just fits inside the government specified
spectral mask of 200 kHz. In order to make this possible, an advanced, DSP-controlled limiter is used to
prevent signal peaks from exceeding the maximum
allowed bandwidth, but not cause distortion.
The result of all this is that the audio quality is outstanding, rivaling a hard-wired microphone. The system delivers a very wide dynamic range, and can handle loud
signal peaks without distortion.
Servo Bias Input and Wiring
The LMb input preamp is a unique design that delivers
audible improvements over conventional transmitter
inputs. The transmitters are 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. Simplified 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 instruments and line level signal sources.
®
Rio Rancho, NM
3
LMb
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.
No Pre-Emphasis/De-Emphasis
Because the signal to noise ratio of the Digital Hybrid
Wireless
ventional pre-emphasis (HF boost) in the transmitter
and de-emphasis (HF roll off) in the receiver. Thus, the
potential distortion problems associated with pre-emphasis and de-emphasis are eliminated.
®
system is so high, there is no need for con-
LMb Block Diagram
Input
Jack
+5V
Shunt
Limiter
Input
Preamp
Servo Bias
Supply
Gain
Adj
Bias Voltage
0, 2 or 4V
HI/Lo
Pass
Filter
Limiter Control
A-D
Converter
AUDIO
I2S
Pilot Tone Squelch
The squelch system in a receiver is a method of muting
the audio when the RF signal conditions are too poor
to produce usable audio. While not all squelch systems
work the same way, the goal is always the same: to
discard noise and unusable audio.
The Digital Hybrid Wireless system employs a DSPgenerated supersonic tone (pilot tone), using it as a
kind of signature, so the receiver can mute even strong
signals that aren’t from the appropriate transmitter. The
pilot tone also helps to ensure that the receiver is quiet
when the transmitter is turned on and off.
256 different pilot tones provide reliable operation in
multi-channel wireless systems. A different tone is
generated every 100 kHz across the tuning range of
the system, so that a tone is not repeated until it is 25.6
MHz above or below the previous one.
D-A
Converter
I2S
Encoded
Audio and
Pilot Tone
(2) AA
Batteries
Buffer Amp
and Filter
Switching
Power
Supply
Tricolor
Power
LED
AUDIO
LMb Transmitter
Driver
Filters
(3)
Final
Amplifier
LECTROSONICS, INC.
Microprocessor
DSP Clock
Oscillator
Oscillator
4
Bicolor
Modulation
LEDs
Micro Clock
PLL Ref
Phase Locked Loop
Keypad
Voltage Controlled
Oscillator
Control
Battery Installation
The transmitter is powered by two AA batteries. We
recommend using alkaline, lithium, or rechargeable
batteries for longest life. Standard zinc-carbon batteries
marked “heavy-duty” or “long-lasting” are not adequate.
The battery status circuitry compensates for the difference in voltage drop between alkaline and lithium batteries across their usable life, so it’s important to select
the correct battery type in the menu.
Because rechargeable batteries run down quite abruptly, using the Power LED to verify battery status will not
be reliable. However, it is possible to track battery status
using the Battery Timer function available in Lectrosonics Digital Hybrid Wireless
Push outward on the Battery Compartment Door and lift
it to open.
®
receivers.
Digital Hybrid Wireless Belt-Pack Transmitter
close but the unit will not operate.
The battery contacts can be cleaned with alcohol and
a cotton swab, or a clean pencil eraser. Be sure not
to leave any remnants of the cotton swab or eraser
crumbs inside the compartment.
Series connection plate
Contact springs
Belt Clips
The wire belt clip may be removed by pulling the ends
out of the holes in the sides of the case. Use pliers to
grasp the wire and avoid scratching the surface of the
housing. Pliers also help when installing the clip.
An optional spring-loaded, hinged belt clip (model number BCSLEBN) is also available. This clip is attached by
removing the plastic hole cap on the back of the housing and mounting the clip with the supplied screw.
Insert the batteries according to the markings inside the
battery compartment.
Battery polarity is marked inside the compartment
If the batteries are inserted incorrectly, the door will
Rio Rancho, NM
5
LMb
Operating Instructions
IR Sync
Port
Slide door
outward
to open
battery
door
FCCID:DBZLMBC1
Lectrosonics, Inc.
Made in U.S.A.
Battery Status LED Battery icon
Belt clip mounting hole
614.4 - 691.1 MHz
S/N XXXXX
Model: LMBC1
IC: 8024A-LMBC1
RF Indicator
5
A
623.400
-40
-20
0
Power Button
Reserved for Future Use
Input Jack
Menu
navigation
buttons
Programmable
Switch
BAT
-10
Move switch
toward the white
dot to turn it on
Power/Function
LED
Modulation
LEDs
-20
-10
BAT
-20
Battery Status LED Indicators
Alkaline, lithium or rechargeable batteries can be used
to power the transmitter. The type of batteries in use are
selectable in a menu on the LCD.
When alkaline or lithium batteries are being used, the
LED labeled BATT on the keypad glows green when the
batteries are good. The color changes to red when the
they are nearing the end of life. When the LED begins to
blink red, there will be only a few minutes remaining.
The Power/Function LED on the top panel will mirror the
keypad LED unless the programmable switch is set to
the Mute or Talkback mode, and the switch is turned on.
The exact point at which the LEDs turn red will vary
with battery brand and condition, temperature and
power consumption. The LEDs are intended to simply
catch your attention, not to be an exact indicator of
remaining time.
A weak battery will sometimes cause the LEDs to glow
green immediately after the transmitter is turned on, but
it will soon discharge to the point where the LED will
turn red or the unit will turn off completely.
Rechargeable batteries give little or no warning when
they are depleted. If you wish to use these batteries in
the transmitter, you will need to manually keep track of
the operating time to prevent interruptions caused by
dead batteries. Start with a fully charged battery, then
measure the time it takes for the Power LED to go out
completely.
NOTE: The battery timer feature in many
Lectrosonics receivers is very helpful in measuring
battery runtime when using rechargeable batteries.
Refer to the receiver instructions for details on
using the timer.
Powering On in Operating Mode
Press and hold the Power Button for several seconds
until a counter on the LCD progresses from 1 through
3, followed by a display of the model, firmware version,
frequency block and compatibility mode.
Hold
for
Rf On
...3
LMB
V1.00
Blk. 19
Hybrid
When you release the button, the unit will be operational with the RF output turned on and the Main Window
displayed. Only the second and third screens will appear when the programmable function switch is used to
turn on the power.
b 19
5
1
494.500
-40
-20
0
6
LECTROSONICS, INC.
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