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DMX-4 USB Mixer User Manual
5
General description:
The DMX-4 is a 4 channel microphone preamplifier with
4 analog to digital converters (A/D). The DMX-4
connects to a PC via a USB 2.0 connection so that audio
can be recorded onto the PC’s hard drive. There are 2
configurable monitor outputs, which can be
independently set to be a mix of any combination of the
4 input channels. The monitor outputs can be used to
connect to a PA system or for video/teleconferencing.
All level adjustments are solid state; there are no
mechanical knobs on the unit. Level adjustments are
made by moving virtual slider controls in the Antex
Mixer Program running on the PC. This allows for
settings to be stored and retrieved as a “scene”. Also, if
the PC connected to the DMX-4 is connected to a LAN,
adjustments can be made from a remote computer
somewhere on the LAN.
The microphone inputs are professional balanced XLR
connectors. The differential input impedance is 2K.
Phantom power of +14 volts can be turned on under
control of the Antex Mixer Program. Phantom power is
connected through a 1K resistor on each line. In
“microphone” setting, all 4 inputs have a gain range of
+10dB to +85dB. Note that 65dB of gain is done in the
analog circuitry, and the additional 20dB is done in the
digital domain. As you increase the gain on any input,
the level of this audio will get louder in the monitor
output and in the recording level. However, once you
exceed 65dB, the recording level will continue to
increase, but the audio in the monitor output will not
increase any further. Input channels 1 and 2 have a
DMX-4 USB Mixer User Manual
6
fixed gain of 0dB in “line” setting. Inputs 3 and 4 have
an adjustable gain of –8 to +31.5dB in “line” setting.
(Although the circuitry is capable of a lower gain setting
than –8dB, the setting is limited in the Antex Mixer
Program to –8dB so that it is not possible for the analog
circuitry to go into clipping before the A/D.)
The monitor outputs are single ended RCA jacks,
capable of a 2VRMS signal (+6dBV). The level
adjustment range is from –102dB to +25.5dB. The
output has a 560 ohm internal series resistance to
protect it from short circuits to ground. The equipment
that the monitor output is connected to should have an
input impedance of 2K or greater.
The A/D converter sample rate can be set to 8, 11.025,
12, 16, 22.05, 24, 32, 44.1, or 48KHz. This allows for
optimization between file size and audio fidelity. All 4
inputs are digitized separately, and 4 tracks may be
recorded to hard disk. The inputs may be mixed in any
combination to the 4 record channels using the Antex
Mixer Program. On your PC, the 4 record channels are
accessed as 2 stereo Wave Devices. Record channels 1
and 2 are left and right of Wave Device 1, respectively,
and record channels 3 and 4 are left and right of Wave
Device 2.
Power input to the DMX-4 can be from +5 to +15 VDC.
Power consumption is about 5 watts. The unit is
supplied with a 9V international wall adapter, but can
also be powered by battery packs or from an automobile
accessory plug (“cigarette lighter”). The power indicator
LED changes gradually from green at 12 volts to red at 5
volts so the user can note a color shift on battery power
when the battery gets low.