9
Inputs and Outputs
Mic/Line Inputs
The MD-4 has four inputs compatible with analog
microphone and line-level signals. Low-noise, wide
dynamic-range microphone preampliers ensure
high-quality audio. Compatible input sources include
dynamic and phantom-powered condenser micro-
phones, and professional or consumer line-level
sources.
Microphone Preamplifiers
The microphone preamps on the MD-4 offer up to 70 dB
of analog gain. These preamps are routed to high-per-
formance 24-bit analog-to-digital converters (ADC).
The gain of each input is selectable from among 20
calibrated values: 0 dB and 10 dB for line- and con-
sumer-line-level inputs, and 19–70 dB in 3 dB steps
for microphones. 48 volt phantom power for condenser
microphones is available on each input. A high-pass
lter (HPF) can be enabled to reduce the presence of
unwanted low-frequency content typically associated
with hum, rumble, or wind noise.
Line-Level Inputs
The input gain settings of 0 dB (unity) and 10 dB sup-
port connection of balanced and unbalanced line-level
signals. Typical nominal levels for these sources would
be +4 dBu and –10 dBV, respectively. Devices provid-
ing these analog signal sources could include audio
consoles, wireless microphone receivers, and broadcast
playback equipment.
Input Meters and Indicators
An 8-segment LED meter is associated with each of the
inputs. The meters are calibrated in dBFS. LEDs display-
ing the on/off status of phantom power and high-pass
lter (HPF) are present on each input. For front-panel
space efciency the four inputs share a common control
section which includes a two-digit LED display and four
pushbutton switches. The LED display indicates the
gain in dB of a selected input. The buttons allow rapid
adjustment of input gain and toggling phantom power
and high-pass lter (HPF) functions.
Analog Input Reference Level
Set from the factory, a nominal +4 dBu analog signal
at the input set for 0 dB gain results in a digital output
signal on the Dante network of –20 dBFS. This corre-
sponds to analog input signals with maximum levels of
+24 dBu resulting in a digital output of 0 dBFS. Rear
panel DIP switches offer the following options.
+4 dBu = –20 dBFS (default,
SMPTE-compliant)
0 dBu = –20 dBFS
0 dBu = –18 dBFS (EBU compliant)
Input Electrical Characteristics
The inputs are electronically balanced (differential),
capacitor-coupled, and ESD (static) protected for
reliable operation in demanding applications. Extensive
ltering minimizes radio frequency (RF) interference.
The inputs are suitable for use in studio, mobile, and
eld environments.
Input XLR connectors are wired with pin 2 signal high
(+), pin 3 signal low (–), and pin 1 common/shield.
When connecting an unbalanced source, connect signal
high (+) to pin 2 and signal low/shield (–) to both pin 1
and pin 3. If this unbalanced topology results in hum or
noise on the mic/line input, connect signal high (+) to
pin 2 and signal low/shield (–) only to pin 3; leaving pin
1 open (“oating”).
Selecting an Input for Control
The MD-4 provides one set of controls for input gain,
phantom power, and high pass ltering. The controls
consist of two pushbutton switches to raise or lower the
input gain, a pushbutton switch to select 48 V phantom
power, and a pushbutton switch to select the on or
off status of the high-pass lter. A 2-digit LED display
indicates the selected input’s gain setting.
Each input has an adjacent pushbutton switch, labeled
SEL, to select for control. Press (momentarily) a chan-
nel’s select button; the input is available for control.
the adjacent blue LED will light to show that the input is
available to control. Only one input can be controlled at
a time.
