ST-UMX3 Universal Audio Mixer
The universal audio mixer shall be an RDL ST-UMX3. The unit shall provide three balanced inputs and one balanced output. Each input and output shall be switch-selectable between mic-level and line-level. Input signal mixing shall incorporate active mixing techniques.

Microphone inputs shall be electronic balanced bridging with an input impedance no less than 600 O and shall be fully compatible with either an unbalanced or balanced audio source. A single turn continuously adjustable trimming control shall be provided to set the microphone gain to produce the rated output level for a microphone input level between -56 dBu and -18 dBu. External phantom voltage shall not be connected to any mic input of the unit. Line inputs shall be electronic balanced bridging with an input impedance no less than 50 kOhms and shall be fully compatible with either an unbalanced or balanced audio source. A single turn continuously adjustable trimming control shall be provided to set the line gain to produce the rated output level for a line input level between -17 dBu and +25 dBu.

The unit shall provide a mic input audio frequency response of 50 Hz to100 kHz (± 1 dB) with intermodulation distortion of <0.04% and a noise floor exceeding 70 dB below the normal rated output level with the input adjusted to 50 dB gain. The unit shall provide a line input audio frequency response of 10 Hz to 100 kHz (± 0.05 dB) with total harmonic distortion plus noise of <0.006%, intermodulation distortion of <0.008% and a noise floor exceeding 82 dB below the normal rated output level with the input adjusted to unity gain. Each mic input shall provide common mode rejection greater than 60 dB. Each line input shall provide common mode rejection greater than 50 dB from 50 Hz to 120 Hz. The unit shall provide headroom of no less than 18 dB above the normal rated output levels.

The unit shall provide a balanced output that can be switched between providing a line-level or microphone-level output signal. The switch shall be a two-position long-life wiping-action slide switch designed for use in audio circuits. The unit shall provide a line-level balanced audio output at a nominal rated output level of +4 dBu with an output impedance of 150 O. The output circuit shall be configured to produce an unbalanced output of proper phase between the positive output leg and ground. The unit shall provide a mic-level balanced audio output at a nominal rated output level of 50 dB below the normal line-level output.

The nominal output audio level shall be displayed according to a VU average metering ballistic on two LED indicators with 0 dB calibrated to the +4 dBu line-level output. A green LED shall display a correlated linear minimum to maximum intensity for signal levels of -15 dB to 0 dB. A red LED shall indicate signals exceeding 0 dB.

The unit shall be constructed in an electrically non-conductive, thermally conductive enclosure. Internal circuitry shall be protected from moisture and vibration using a thermally conductive compound that permanently secures the circuitry within the enclosure.

The face of the unit shall provide graphical labels identifying wiring connections and operating controls. Indicators shall be oriented toward the front edge of the unit. Controls and switches shall be oriented toward the face of the unit.

Connection to external wiring shall be provided using a fixed terminal block on the edge of the unit. The terminal block shall accept wiring gauges from 14 to 22 and shall include a positive electrically conductive mechanism to prevent wire abrasion by the terminal screws.

The unit shall measure 3” (7.6 cm) x 1.6” (4 cm) x 0.7” (1.7 cm) and be compatible with all RDL STICK-ON mounting accessories. The unit shall be supplied with a two part re-closable polypropylene fastener system equipped with a rubber adhesive that bonds to low surface energy materials.

Power requirements shall be 24 Vdc ground-referenced with a maximum current not exceeding 55 mA. The unit shall utilize an external power supply. 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 55 degrees C. The unit shall comply with relevant EMC requirements and shall bear the CE marking.

The unit shall be an RDL ST-UMX3.