Antex Electronics DMX-88 USB Recording Mixer - Manual (Page 4)

DMX-88 USB Mixer User Manual
4
General description:
The DMX-88 is an 8 channel input, 2 channel output, USB audio interface. It is intended to be connected to a host computer that will
record the audio on to the computer’s hard drive. The DMX-88 will take up to 8 inputs, either microphone or line level, digitize them,
and send 8 channels of audio data to the attached computer via the USB 2.0 connection. The DMX-88 is also capable of playing back
2 channels of audio data, combined into a mono signal, to a PA and a headphone output on the unit. This output can be either the
playback signal from the host computer, or an analog “monitor all” combination of all 8 inputs, or a blend of the 2. There are 2
independent analog monitor outputs, which are a selectable mix of any of the 8 inputs. These can be used as a “mix minus” output to
a telephone interface or video conferencing system.
The inputs are balanced and utilize high quality instrumentation amplifiers. The connectors are XLR. Each input can be independently
configured as line level or microphone level, and can have 48 volt phantom power on or off. Selecting microphone level boosts the
gain by 46dB. There is a trim setting on each input. Each input channel also has an analog compressor/limiter and noise gate. The
compressor/limiter prevents clipping of the analog to digital converter (A/D), effectively increasing the headroom by about 20dB. The
noise gating reduces the background noise in the recording and on the monitor outputs when no one is talking into the microphone.
The DMX-88 is designed for voice recording, and there is a 2 pole 100 Hz high pass filter on each input.
All controls are set using the Antex Mixer Program running on the computer; there are no mechanical knobs or switches on the
DMX-88. Because the settings are done via software, “scenes” can be saved on the host computer hard drive and restored to easily
set a particular configuration of settings. One scene is also stored in non-volatile EEPROM memory on the DMX-88. This EEPROM is
read on power-up and sets all the controls on the DMX-88. If the DMX-88 is moved to a different computer, it still retains the same
settings. Whenever the Antex Mixer Program is closed, the settings are updated in the EEPROM.
The monitor outputs are balanced, but can be connected to single ended equipment by grounding one of the balanced signals. Each
monitor output can be a mix of any of the 8 inputs. The monitor mix and output level are controlled by the Antex Mixer Program.
There is a headphone output and a PA output. The signal is the same on each output. The headphone output is designed to drive low
impedances, 8 to 32 ohms, and the PA output is balanced, using the same drive chip as the monitor outputs. The headphone
output is not grounded. Do not connect to grounded equipment; it is intended for headphones only. If connected to
ground, the output will be short circuited and cause the amplifier chip to go into thermal shutdown mode. The signal can
either be an analog mix of all inputs, or a mono mix of the stereo playback from the computer, or a mix of the two. There are 2
separate slider controls on the Antex Mixer Program to control the level of the monitor all and playback signals. Computer playback
can be used for confidence monitoring of what has actually been recorded on the hard drive, or for in court playback of previous
testimony.