User's Manual

HMa
LECTROSONICS, INC.
4
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 ana-
log systems, plus the excellent audio fidelity typical of
pure digital systems.
General Technical
Description
The transmitter uses a standard 3-pin XLR input jack
for use with any microphone with a mating XLR con-
nector. An LCD, membrane switches and multi-color
LEDs on the control panel make input gain adjust-
ments 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.
Along with providing peerless audio quality with wide
frequency response and dynamic range in Nu Hy-
brid mode, the technology used in the HMa includes
compatibility modes for Lectrosonics Mode 3 and
IFB receivers. Companion receivers are covered in
separate manuals. 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 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 de-
gree, and all wireless microphone systems seek to mini-
mize the impact of that noise on the desired signal. Con-
ventional 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 over-
come 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 informa-
tion 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, yield-
ing audio performance that rivals that of wholly digital
systems, without the power and bandwidth problems
inherent in digital transmission.
Bias Voltage
42V,15V, 5V
+4V
Input
Amp
Shunt
Limiter
AUDIO
FREQ
UP
DWN
Reference
Crystal
Reference
Crystal
3 V
Battery
Hi.Lo
Pass
Filter
Digital
Pot
Audio
Level
Phantom
Power
Audio
A-D
Converter
11001001
D-A
Converter
11001001
Control Panel
Microprocessor
Voltage
Controlled
Oscillator
Final
Amplifier
Filter
Amp
Encoded Audio
and Pilot Tone
Bicolor
Modulation
LEDs
Switching
Power
Supply
Digital Signal Processor
Phase Locked Loop
LCD
1.2V
4V
-3.3V
+3.3V