Instruction Manual

DPR-A
LECTROSONICS, INC.
4
Outstanding Audio Performance
The audio performance of the overall hybrid system is
depicted in the graph below. Distortion in the system is
extremely low over the entire audio bandwidth.
No Pre-Emphasis/De-Emphasis
The Digital Hybrid Wireless
®
design results in a signal-to-
noise ratio high enough to preclude the need for con-
ventional pre-emphasis (HF boost) in the transmitter and
de-emphasis (HF roll-off) in the receiver. This eliminates
the potential for 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 25, 35, 50, 70, 100, 120 and 150 Hz to con-
trol 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 trans-
mitter into limiting, or in the case of high level sound
systems, even cause damage to loudspeaker systems.
The roll-off is normally adjusted by ear while listening
as the system is operating.
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 distor-
tion. 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 re-
ceiver’s squelch. A pilot tone squelch system provides
a reliable method of keeping a receiver output muted
(squelched) even in the presence of significant interfer-
ence.
Control Panel
The control panel includes five membrane switches and
an LCD screen to adjust the operational settings. Multi-
color LEDs are used to indicate audio signal levels for
accurate gain adjustment, battery status and encryp-
tion key function.
Alternate Recording Function
The DPR has a built in recording function for use in
situations where RF may not be possible or to work as
a stand alone recorder. The record function and trans-
mit functions are exclusive of each other - you cannot
record AND transmit at the same time. When the unit
is transmitting and recording is turned on, the audio in
the RF transmission will stop, but the battery status will
still be sent to the receiver.
The recorder samples at 44.1kHz rate with a 24 bit
sample depth. (the rate was selected due to the re-
quired 44.1kHz rate used for the digital hybrid algo-
rithm). The micro SDHC card also offers easy firmware
update capabilities without the need for a USB cable or
driver issues.
Encryption
When transmitting audio, there are situations where
privacy is essential, such as during professional
sporting events, in court rooms or private meetings.
For instances where your audio transmission needs
to be kept secure, without sacrificing audio quality,
Lectrosonics introduces Encryption Keys. Truly entro-
pic encryption keys are first created by a Lectrosonics
receiver, such as the DSQD Receiver. The key is then
synced with the DPR via the IR port. The audio will
be encrypted and can only be listened to if both DPR
and receiver have the matching encryption key. If you
are trying to transmit an audio signal and keys do not
match, all that will be heard is silence or white noise.