DMX88 Specifications 30 August, 2011

Transcription

1 DMX88 Specifications 30 August, 2011 General Description: This unit is an 8 channel USB audio interface. It is intended to be connected to a computer, that will record the audio on the computer s hard drive. The DMX88 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 connection. The DMX88 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, or a monitor all combination of all 8 inputs, or a blend of the 2. There are 2 independent 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 with XLR connectors, utilizing high quality instrumentation amplifiers. Each 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. The input channels also have an analog limiter/noise gate. The limiter prevents clipping of the analog to digital converters (), 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 DMX88 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 app running on the computer; there are no mechanical knobs or switches on the DMX88. 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 nonvolatile EEPROM memory on the DMX88. This EEPROM is read on powerup and sets all the controls on the DMX88. If the DMX88 is moved to a different computer, it still retains the same settings. Whenever the Antex Mixer app 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 app. 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, 4 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 trim controls on the Antex Mixer app 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. There are 8 red/green indicator LEDs on the front of the unit, corresponding to each input channel. The LED will light green to indicate activity when someone is speaking into the microphone. The LED will turn red to indicate that limiter is active. These indicators are also mimicked in the Antex Mixer app, with a 3 color indicator. Green indicates activity, yellow that the limiter is active, and red to indicate the preamp is clipping. There is a pair of red and green Device Number LEDs. If more than one DMX88 is connected to the same computer, each one will have a different LED pattern to tell them apart. The LED

2 pattern is mimicked in the Antex Mixer app so the user knows which unit being controlled by which Mixer app instance. There is a standby mode for reduced power consumption. When the unit is first poweredup, the power LED will flash, indicating standby mode. All internal electronics is powered down except the USB microcontroller. We the unit is connected to a computer and enumerates, it will come out of standby and the power LED will stop flashing and glow steadily. Inputs: Number 8 Type Transformerless balanced (instrumentation amp) Connector Female XLR Impedance to ground 1K Sensitivity, Line setting 31dBV Sensitivity, Microphone setting 77dBV (Sensitivity is the input signal level which corresponds to full scale with the input trim set to maximum gain. Note that full scale may not be possible because the limiter becomes active approximately 2dB below full scale.) Maximum input level before transient protection begins clipping 21dBV Limiter threshold 2dB below full scale Limiter headroom 20dB Noise gate threshold 32dB below full scale (Note that the limiter and noise gate thresholds are soft.) Phantom power voltage 48V Phantom power impedance 6.8K on hot and cold, 3.4K effective Trim control type Electronic (solid state) Trim control step size 0.5dB High pass filter, 12dB per octave slope Monitor Outputs: Number 2 Type Transformerless balanced (Note: May be used as unbalanced by grounding one of the signal lines.) Connector ¼ TRS Mix Any combination of the 8 inputs Level control type Electronic (solid state) Level control step size 0.5dB Maximum output level 21dBV Headphone Output: Connector ¼ TRS Output power 500mW (16 ohm load, THD = 1%) Source D/A output or analog mix of all inputs Level control type Electronic (solid state) Level control step size 0.5dB PA Output: Connector ¼ TRS Type Transformerless balanced (Note: May be used as unbalanced by grounding one of the signal lines.)

3 Source D/A output or analog mix of all inputs Level control type Electronic (solid state) Level control step size 0.5dB Maximum output level 7dBV Digital audio: Number of record channels 8 Number of playback channels 2 Bit depth 24 Sample rates 8, , 12, 16, 22.05, 24, 32, 44.1, 48KHz USB: Specification 2.0, high speed Audio data transfer packet type Bulk Control data packet type Interrupt Indicators: On unit, red/green LED for each input. Green indicates activity, red indicates limiter active. Power LED Red and Green Device Number LEDs Power: Internal power supply with detachable IEC cord, VAC. Dimensions: 13 inches wide, 10 inches deep, Max height 1U (1.75 ). Rack ears optional for 19 inch rack mounting. Weight: 3.6 pounds, 3.85 pounds with rack ears

4 CH1 CH2 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH1 OUT CH3 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH2 OUT CH4 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH3 OUT CH5 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH4 OUT USB ENGINE USB 2.0 CH6 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH5 OUT CH7 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH6 OUT D/A PB_LEFT CH8 LINE=0dB, MIC=46dB 95dB TO 31.5dB CH7 OUT D/A PB_RIGHT LINE=0dB, MIC=46dB 95dB TO 31.5dB CH8 OUT

5 CH1 OUT CH2 OUT CH3 OUT CH4 OUT CH5 OUT CH6 OUT CH7 OUT CH8 OUT 95dB TO 31.5dB 10dB MONITOR 1 MONITOR 2 95dB TO 31.5dB 10dB MONITOR ALL HEADPHONE 95dB TO 31.5dB PB_LEFT PB_RIGHT PA PLAYBACK 95dB TO 31.5dB