Lectrosonics DSR4 - Technical Description; Compatibility Modes; Encryption; Smart Noise Reduction (SmartNR)

Four Channel Digital Receiver
Rio Rancho, NM
5
Technical Description
The DSR4 digital 4-channel receiver is a much-requested,
versatile slot receiver, equally appropriate for bag use, as
well as reality TV and run and gun applications.
Extremely high Third Order Intercept (IP3) performance of
+15 dBm, 24-bit/48 kHz audio performance, and AES-
256 CTR mode encryption ensure that professionals in
all audio disciplines have the tools needed to get the job
done, even in extremely tough environments.
Compatibility Modes
The DSR4 receiver was designed to operate with Lec-
trosonics digital transmitters from the D2, DCH and M2
series. The receiver is also backward compatible with
Digital Hybrid Wireless® transmitters including those
with NA Hybrid, NU Hybrid, JA HYBRID and EU Hybrid
modes.
Encryption
The DSR4 receiver features AES 256-bit, CTR mode en-
cryption, with 4 dierent key policies available.
Diversity Options
An ideal diversity system constructively combines all the
energy available at both antennas. The DSR4 oers two
diversity options: for 4-channel operation, each channel
combines signals from both antennas in or out of phase,
depending on eld strength at each antenna and which
combination yields the best results. For 2-channel opera-
tion, receivers can be paired for Vector Diversity opera-
tion. The Vector subsystem smoothly and continuously
combines RF signals from both channels, with diering
phase angles in order to obtain maximum energy. The
four receivers in the DSR4 can be use separately or com-
bined in pairs.
RF Frequency Tracking Front-End
In addition to the extremely high IP3 capability of the
receiver, to signicantly reduce unwanted interference
and intermodulation problems, the DSR4 has a frequency
selective front-end section that tracks and tunes to the
desired signal frequency and rejects unwanted interfer-
ing signals. The low noise, high current RF amplier
was designed with feedback regulation for stability and
precise gain in order to handle stronger RF signals with-
out output overload. This produces a robust front-end
that is as selective as xed single frequency designs and
is suitable for use in close proximity to other receivers
and transmitters commonly used in eld production bag
systems.
Smart Noise Reduction (SmartNR
™
)
The DSR4 has been meticulously designed using the
best available low noise components and techniques.
Nonetheless, the wide dynamic range of digital and
Hybrid transmission technology, combined with at
response to 20 kHz, makes it possible to hear the -120
dBV noise oor in the transmitter’s mic preamp, or the
(usually) greater noise from the lav microphone itself.
(To put this in perspective, the noise generated by the
recommended 4k bias resistor of many electret lavaliere
mics is –119 dBV and the noise level of the microphone’s
electronics is much higher.) In order to reduce this noise
and thus increase the eective dynamic range of the
system, the DSR4 is equipped with a selectable Smart
Noise Reduction algorithm, which removes hiss without
sacricing high frequency response.
The Smart Noise Reduction algorithm works by attenuat-
ing only those portions of the audio signal that t a statis-
tical prole for randomness or “electronic hiss.” Desired
high frequency signals having some coherence such as
speech sibilance and tones are not aected.
The Smart Noise Reduction algorithm has three modes
- OFF/NORMAL/FULL - selectable from a user setup
screen. When switched OFF (the default setting for
digital compat modes) no noise reduction is performed
and complete transparency is preserved. All signals
presented to the transmitter’s front end, including any
faint microphone hiss, will be faithfully reproduced at
the receiver. When switched to NORMAL, (the factory
default setting for Hybrid modes) enough noise reduc-
tion is applied to remove most of the hiss from the mic
preamp and some of the hiss from lavaliere microphones.
The noise reduction benet is dramatic in this position,
yet the degree of transparency maintained is exceptional.
When switched to FULL, enough noise reduction is ap-
plied to remove most of the hiss from nearly any signal
source of reasonable quality, assuming levels are set
properly at the transmitter. This additional noise reduc-
tion comes at the cost of some transparency for low-
level room noise, yet the algorithm remains undetectable
under most circumstances.
Audio Output Level
A setup screen is provided for adjusting the audio output
level in 1 dB increments from -50 to +7 dBu using the
front panel MENU/SEL, UP, and DOWN buttons.
Test Tone
To assist in matching the audio levels of equipment con-
nected to the DSR4, a 1 kHz audio test tone, adjustable
from -50 to +7 dBu in 1 dB increments, is available at the
outputs. If using AES3 outputs, the level is xed and can-
not be adjusted.
Power Supply
The DSR4 is operated from an external DC power source
(DCR15/4AU recommended).The receiver has a built-in
Poly-Fuse for protection. This fuse automatically resets if
the power supply is disconnected for about 15 sec. The
power section also has protection circuits that prevent
damage to the receiver if a positive ground power source
is applied.