Lectrosonics HMAC1 User Manual
HMa
Wideband Plug-On Transmitter
With Digital Hybrid Wireless® Technology
INSTRUCTION MANUAL
Digital Hybrid Wireless
US Patent 7,225,135
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Purchase Date:
®
Rio Rancho, NM, USA
www.lectrosonics.com
HMa
2
LECTROSONICS, INC.
Thank you for selecting a Lectrosonics HMa plug-On
transmitter. The unique design provides several distinct
features for professional applications:
• Outstanding RF operating range
• Superb audio quality
• Corrosion-resistant housing
• Programmable compatibility modes for use with a
wide variety of different receivers
The Digital Hybrid Wireless
®
design (US Patent
7,225,135) combines 24-bit digital audio with analog
FM resulting in a system that has the same operating
range as analog systems, the same spectral efficiency
as analog systems, the same long battery life as analog
systems, plus the excellent audio fidelity typical of pure
digital systems.
The transmitter uses a standard 3-pin XLR input jack for
use with any microphone with a a mating XLR connector. An LCD, membrane switches and multi-color LEDs
on the control panel make input gain adjustments and
frequency and compatibility mode selection quick and
accurate, without having to view the receiver. The housing is machined from a solid aluminum block to provide
a lightweight and rugged package. A special non-corrosive finish resists salt water exposure and perspiration
in extreme environments.
The DSP-based design works with all Digital Hybrid
receivers, and is backward compatible for use with
Lectrosonics 200 and 100 Series and IFB receivers and
some other brands of analog wireless receivers. Companion receivers are covered in separate manuals.
Wideband Digital Hybrid® Plug-On Transmitter
Table of Contents
General Technical Description ...............................................4
Wideband Design ...................................................................4
Digital Hybrid Wireless
No Pre-Emphasis/De-Emphasis ............................................4
Low Frequency Roll-Off .........................................................4
Input Limiter ...........................................................................5
Signal Encoding and Pilot Tone .............................................5
Microprocessor and DSP .......................................................5
Compatibility Modes ...............................................................5
Control Panel .........................................................................5
Battery Options and Operating Time .....................................5
Frequency Blocks and Bands ................................................5
Controls and Functions ..........................................................6
LCD Screen ...........................................................................6
Power LED .............................................................................6
Audio Input Jack .....................................................................6
Battery Compartment.............................................................6
Modulation LEDs ....................................................................6
Audio Button ..........................................................................6
Up/Down Arrows and Panel Lockout ......................................6
Antenna ..................................................................................6
Battery Installation ..................................................................7
Attaching/Removing a Microphone .......................................7
Operating Instructions ............................................................8
Power Up and Boot Sequence ...............................................8
Power Down ...........................................................................8
Automatic Power Restore .......................................................8
Standby Mode ........................................................................8
Compatibility Mode Screen ....................................................8
Selecting the Audio Polarity ...................................................8
LCD Backlight Settings ..........................................................9
Selecting Step Size mode ......................................................9
Setting Transmitter Operating Frequency ...............................9
Lock/Unlock Screen ...............................................................9
Audio Screen .......................................................................10
Adjusting the Input Gain .......................................................10
Adjusting the Low Frequency Roll-off ..................................10
Selecting the Phantom Power Supply ..................................10
About the Phantom Power Supply .......................................11
Special Purpose Barrel Adapters .........................................12
MCA-M30 .............................................................................12
Accessories ...........................................................................13
Troubleshooting .....................................................................14
Specifications and Features .................................................16
Service and Repair ................................................................17
Returning Units for Repair ...................................................17
®
Technology ......................................4
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
Rio Rancho, NM
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HMa
Bias Voltage
General Technical Description
Wideband Design
The HMa transmitter uses ±75 kHz wide deviation for
an excellent signal to noise ratio and wide dynamic
range. The DSP controlled input limiter features a wide
range dual envelope design which cleanly limits input
signal peaks over 30 dB above full modulation. Switching power supplies to provide constant voltages to the
transmitter circuits from the beginning (3 Volts) to the
end (1.7 Volts) of battery life, and an ultra low noise
input amplifier for quiet operation.
Digital Hybrid Wireless® Technology
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 and
resistance to interference.
Lectrosonics Digital Hybrid Wireless® systems overcome 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 that can be accomplished
only in the digital domain, even though the inputs and
outputs are analog.
Channel noise still impacts received signal quality and
will eventually overwhelm a receiver. Digital Hybrid
Wireless® simply encodes the signal to use a noisy
channel as efficiently and robustly as possible, yielding audio performance that rivals that of wholly digital
systems, without the power and bandwidth problems
inherent in digital transmission.
Because it uses an analog FM link, Digital Hybrid
Wireless® enjoys all the benefits of conventional FM
wireless systems, such as excellent range, efficient
use of RF spectrum, and resistance to interference.
However, unlike conventional FM systems, it does
away with the analog compandor and its artifacts.
No Pre-Emphasis/De-Emphasis
The Digital Hybrid Wireless® design results in a signal-tonoise ratio high enough to preclude the need for conventional pre-emphasis (HF boost) in the transmitter and
de-emphasis (HF roll-off) in the receiver. This eliminates
the potential for extreme distortion on signals with
abundant high-frequency information.
Low Frequency Roll-Off
The low frequency roll-off can be set for a 3 dB down
point at 35, 50 or 70 Hz to control subsonic and very
low frequency audio content in the audio. The actual
roll-off frequency will vary slightly depending upon the
low frequency response of the microphone.
Excessive low frequency content can drive the transmitter into limiting, or in the case of high level sound
systems, can even cause damage to loudspeaker
systems. The roll-off is normally adjusted by ear while
listening as the system is operating.
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42V,15V, 5V
Shunt
Limiter
Input
Amp
Digital
AUDIO
FREQ
UP
DWN
Bicolor
Modulation
LEDs
Phantom
Power
Pot
LCD
Audio
Level
Hi.Lo
Pass
Filter
+4V
Audio
Microprocessor
Control Panel
A-D
Converter
11001001
Digital Signal Processor
D-A
Converter
11001001
Reference
Crystal
Phase Locked Loop
Reference
Crystal
Encoded Audio
and Pilot Tone
3 V
Battery
Filter
Amp
Switching
Power
Supply
Voltage
Controlled
Oscillator
1.2V
4V
-3.3V
+3.3V
Final
Amplifier
LECTROSONICS, INC.
Wideband Digital Hybrid® Plug-On Transmitter
Input Limiter
A DSP-controlled analog audio limiter is employed
before the analog-to-digital (A-D) converter. The limiter
has a range of more 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, a
fast attack and release limiter followed by a slow attack
and release limiter. The limiter recovers quickly from
brief transients, with no audible side effects, and also
recovers slowly from sustained high levels, to keep
audio distortion low and while preserving short term
dynamics.
Signal Encoding and Pilot Tone
In addition to controlling the limiter, the DSP also
encodes the digitized audio from the A-D converter
and adds an ultrasonic pilot tone to control the receiver’s squelch. A pilot tone squelch system provides
a reliable method of keeping a receiver output muted
(squelched) even in the presence of significant interference. When the system is operating in the hybrid
mode, a different pilot tone frequency is generated for
each carrier frequency to prevent inadvertent squelch
problems and simplify multi-channel coordination.
Microprocessor and DSP
A microprocessor monitors user command inputs from
the control panel buttons and numerous other internal
signals. It works intimately with the DSP to ensure the
audio is encoded according to the selected Compatibility Mode and that the correct pilot tone is added to the
encoded signal.
Control Panel
The control panel includes four membrane switches and
an LCD screen to adjust the operational settings. Multicolor LEDs are used to indicate audio signal levels for
accurate gain adjustment and for battery status.
Battery Options and Operating Time
Switching power supplies convert battery voltages to
operate various circuit stages with maximum efficiency.
Frequency Blocks and Bands
Lectrosonics established a “block” numbering system
years ago to organize the range of frequencies available from the low 500 MHz band to the upper 700
MHz band. Each block includes 256 frequencies in 100
kHz increments. The block number is part of a simple
formula to derive the frequency. The block number is
multiplied by 25.6 to produce the lowest frequency in
the block. For example, block 27 x 25.6 = 691.200.
The HMa transmitter features a wideband tuning range
that covers three blocks. This tuning range is referred
to as a BAND rather than a block.
Band Tuning Range (MHz)
A1 170.100 - 534.575
B1 537.600 - 614.375
C1 614.400 - 691.175
*C1 will not be in use after the results of the next DTV
transition spectrum auction in 2016 are in full effect.
Compatibility Modes
The transmitter was designed to operate with Lectrosonics Digital Hybrid Wirteless® receivers and will yield
the best performance when doing so. However, due to
the flexibility of digital signal processing, the transmitters can also operate in various compatibility modes
for use with Lectrosonics 100 and 200 Series and IFB
receivers. It will also work with certain non-Lectrosonics receivers. Contact your sales representative or the
factory for a complete list of compatible non-Lectrosonics receivers.
Rio Rancho, NM
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HMa
Controls and Functions
Modulation
Input
Coupler
XLR Input Jack
PWR LED
LEDs
LCD
AUDIO Button
UP Arrow
FREQ Button
Battery
Compartment
DOWN Arrow
LCD Screen
The LCD is a numeric-type Liquid Crystal Display with
several screens that allow settings to be made with the
AUDIO, FREQ, UP and DOWN buttons to configure
the transmitter. The transmitter can be turned on in a
Standby mode to make adjustments without the risk of
interfering with other wireless systems nearby. Counters are presented on the LCD enabling this function.
Power LED
The PWR LED glows green when the batteries are
good. The color changes to red when there is about 20
minutes of life left. When the LED begins to blink red,
there are only a few minutes of life.
A weak battery will sometimes cause the PWR LED to
glow green immediately after being put into the unit,
but will soon discharge to the point where the LED will
go red or shut off completely.
Audio Input Jack
The XLR input jack on the transmitter accommodates
most hand-held microphones. Phantom power can
be set at various levels for use with a wide variety of
electret microphones.
Battery Compartment
The battery compartment door is made of machined
aluminum and is hinged to the housing to prevent it
being damaged or lost.
Modulation LEDs
The Modulation LEDs provide a visual indication of the
input audio signal level from the microphone. These
two bicolor LEDs can glow either red or green to indicate modulation levels. Full modulation (0 dB) occurs
when the -20 LED first turns red.
Signal Level -20 LED -10 LED
Less than -20 dB Off Off
-20 dB to -10 dB Green Off
-10 dB to +0 dB Green Green
+0 dB to +10 dB Red Green
Greater than +10 dB Red Red
Audio Button
The AUDIO button is used to display the audio level
setting, low frequency roll-off and phantom power
mode. Repeatedly pressing the button will cycle
through the available settings, allowing the UP and
DOWN arrow buttons to adjust the values.
Freq Button
The FREQ Button displays the selected operating frequency and also toggles the LCD between displaying
the actual operating frequency in MHz and a two-digit
hexadecimal number. Frequencies can be selected in
either 100kHz or 25kHz steps. The appearance of the
hexadecimal number is different in the 100kHz step
size mode than in the 25kHz step size mode.
NOTE: The FREQ and AUDIO buttons are used
together to enter the standby mode and to turn the
power on or off.
Up/Down Arrows and Panel Lockout
The Up and Down arrow buttons are used to select the
operating frequency, adjust the audio level, or set the
Compatibility Mode.
Pressing both arrows simultaneously enters the lock
countdown. Holding the two buttons in until the countdown is completed locks the control panel buttons so
they can only be used to display current settings. “Loc”
is displayed to indicate the controls are locked when a
button is pressed while the panel is locked.
Once locked, the buttons are unlocked by removing
the battery.
Antenna
An antenna is formed between the housing and the attached microphone, operating much like a dipole type.
At UHF frequencies the length of the housing is similar
to 1/4 wavelength of the operating frequency, so the
antenna is surprisingly efficient, which helps extend
the operating range and suppress noise and interference.
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LECTROSONICS, INC.
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