Whirlwind Mic to Line Driver/Headphone Monitor MD-1 - Manual (Page 2)

DRIVER position, the output male XLR connector receives the amplified balanced
output of the MD-1 circuitry. With the switch in LOOP position the output XLR is
connected directly to the female input XLR. This allows the MD-1 to monitor a signal
looping through the unit without altering it. In the LOOP mode the MIC/LINE switch and
GAIN control only affect the headphone amplifier.
After the gain stage, the signal is also presented to the headphone gain and driver circuits
via the MIX control. In full CW position, only the input signal is passed to the
headphones. In the full CCW position, only the signal from the ¼” TRS balanced LINE
IN jack is passed to the headphones. Adjusting the MIX control for the desired balance
varies the level of each signal in the mix. The blended signal passes through the
headphone gain section, which has an audio range of -50dB of attenuation fully CCW to
+56 dBm of gain in the full CW position, and then to the headphone driver circuit. The
headphone driver will produce -6dB of clean audio into 30
Ω
headphones, which is quite
loud! With higher impedance phones the driver can produce 18 Volts peak to peak. Using
30
Ω
headphones at very loud levels continuously can consume a set of batteries in about
2 hours. Battery life can be greatly extended simply by turning the headphone volume
control to the off or CCW position when not listening to the headphones.
Power to the MD-1 is supplied by two 9 Volt batteries accessible via slide out
drawers on the side of the unit. Power is applied to the unit via the power switch. When
the battery voltage falls below 13VDC, the BATT OK LED will not illuminate (the unit
will still work but with reduced headroom).
The MD-1 is housed in a robust steel case that provides superior shielding and durability.
A belt clip is also included and riveted to the enclosure.
CONTROLS AND FUNCTIONS
PH 18V button applies 18VDC phantom power to the input XLR for powering standard
condenser microphones. Operates in MIC mode only.
MIC/LINE button matches the input circuit (rear female XLR jack) to either microphone
or line level sources. Position is IN for mic mode and OUT for line mode.