RU-MLB4	Mic/Line Bi-Directional Network Interface

The Mic/Line Bi-Directional Network Interface shall be an RDL RU-MLB4.  The unit shall provide a Dante compatible Ethernet interface, four mic or line switch-selectable audio inputs and four balanced professional line-level audio outputs. The unit shall convert four networked Dante digital audio channels to analog audio and four analog audio sources to networked Dante digital audio channels.

The unit shall provide network connection through an RJ45 type shielded connector equipped with LEDs for Link and Speed.  The Speed LED shall illuminate when the unit is connected to a Dante network with a transmission speed of 100 Mbps.  The unit shall support a bit depth of 24 bits and sample rates of 44.1 kHz and 48 kHz.  The unit shall convert between digital and analog formats at nominal standard professional levels of +4 dBu for a digital audio value of -18 dBFS.

Four audio inputs shall be provided on detachable terminal blocks.  Each input shall be equipped with a rear-panel switch to select between a microphone or line-level source.  Each line input shall provide connection terminals for either a balanced +4 dBu or unbalanced -10 dBV source. The line input impedance shall exceed 20 kOhms and the mic input impedance shall exceed 1 kOhms. Each input shall provide audio frequency response of 20 Hz to 20 kHz (± 0.5 dB) with total harmonic distortion of less than 0.1%.  Noise below normal operating level shall exceed 70 dB for microphone inputs and shall exceed 75 dB for line inputs.  Microphone inputs shall provide a minimum of 20 dB headroom before hard clipping and line inputs shall provide at least 18 dB headroom.  Crosstalk between any pair and at any gain shall exceed -70 dB from 20 Hz to 20 kHz and -75 dB at 1 kHz. Common mode rejection shall exceed 70 dB for balanced microphone inputs and 60 dB for balanced line inputs between 50 and 120 Hz.

Two line inputs shall be provided for each input channel, one unbalanced at -10 dBV and one balanced at +4 dBu.  The balanced input shall be switch-selectable for line or mic level sources.  Setting the input to mic shall enable P48 phantom voltage for that input.  The internal microphone preamplifier shall be equipped with circuitry to detect the type of microphone connected to the input terminals or corresponding associated microphone jack.  When a condenser microphone is connected, the unit shall automatically set the gain to 40 dB.  When a dynamic microphone is connected, the gain shall automatically be set to 60 dB.  The gain setting shall be fully automatic and shall require no hardware or software setting by either the installer or user.

The unit shall provide a green LED signal presence indicator that varies in intensity as a visual indication of the relative audio level at each of the four channel inputs.  The indicator shall provide positive visual indication of signal presence for signals exceeding an amplitude 20 dB below a normal operating level of -18 dBFS.

Four audio outputs shall be provided on detachable terminal blocks.  Each output shall produce a balanced professional +4 dBu signal level for a nominal network digital audio level of -18 dBFS.  The output impedance shall be 150 O balanced or 75 O unbalanced. The output circuit shall be configured to produce an unbalanced output of proper phase between the positive output leg and ground. The unit shall, for each output, provide audio frequency response of 20 Hz to 20 kHz (± 0.5 dB) with total harmonic distortion of less than 0.05% and a noise floor exceeding 80 dB below the normal rated output level of +4 dBu, and a minimum of 18 dB of headroom above the normal rated output level of +4 dBu.  Crosstalk between any pair shall exceed -85 dB from 20 Hz to 20 kHz. During the absence of all digital audio inputs, the outputs shall fully mute with a residual noise at least 95 dB below the normal rated output level of +4 dBu.

The unit shall provide a green LED signal presence indicator that varies in intensity as a visual indication of the relative audio level at each of the four channel outputs.  The indicator shall provide positive visual indication of signal presence for signals exceeding an amplitude 20 dB below a normal operating level of +4 dBu.

The front face of the unit shall provide graphical labels protected beneath a polycarbonate protective surface.  The front face shall include LED indicators to indicate the presence of unit power, audio signals and Dante system and synchronization lock. 

The unit shall measure 5.8" (15 cm) W; 1.7" (4.3 cm) H; 5.2" (13.2 cm) D and be compatible with RDL RACK-UP mounting accessories.  The unit’s electrical chassis shall be fully constructed of metal, comprised of aluminum and steel members.  The chassis shall include an integral provision for surface mounting.

The unit shall be equipped to operate from a 24 Vdc ground-referenced power supply with a maximum current not exceeding 180 mA plus connected phantom loads. The unit shall utilize an external power supply connected through one of two power inputs, one detachable terminal block or one dc jack. The unit shall be engineered, assembled and tested in the U.S.A. and be specified for continuous duty in professional installed systems. The unit shall be specified for operation in an ambient temperature between 0 and 40 degrees C. The unit shall comply with relevant EMC requirements and shall bear the CE marking.

The unit shall be an RDL RU-MLB4.