ST-LEQ1 Loudness Equalizer
The loudness equalizer unit shall be an RDL ST-LEQ1. The unit shall provide two line-level inputs and one line-level output. One input shall be designated to be equalized, typically music, and one input shall be designated to not be equalized, typically paging. These inputs shall be designated as equalized (EQ) and direct (DIRECT IN) respectively. A 0 to 10 Vdc ramp input shall be provided to set the specific loudness curve applied to the audio output.

Each input shall be electronic balanced bridging with an input impedance no less than 30 kOhms and shall be fully compatible with either an unbalanced or balanced audio source. The rated input level for each audio input shall be +4 dBu.

One continuously adjustable multi-turn trimming control shall be provided. The control shall adjust the midrange attenuation, centered at 1 kHz, from flat to -15 dB when the 0 to 10 Vdc ramp input voltage is less than or equal to 5 Vdc (maximum 1 kHz attenuation). For ramp input voltages between 0 Vdc and 5 Vdc, the unit shall attenuate the midrange frequencies by the value in dB set using the trimming control.  For ramp input voltages from 5 Vdc to 10 Vdc, such attenuation shall be reduced in proportion to the ramp voltage, becoming flat at 10 Vdc. The equalization “Q” and the attenuation applied to the unit output shall correspond to the “Maximum equalization for different control voltages” graph published in the RDL datasheet for the ST-LEQ1.

The unit shall provide an audio frequency response of 10 Hz to 40 kHz (± 1 dB) with total harmonic distortion plus noise <0.005% (20 Hz to 20 kHz) when set for flat response and a noise floor exceeding 90 dB below the normal rated output level. The audio inputs shall attenuate common mode signals by a minimum of 50 dB from 50 to 120 Hz.  The unit’s audio output headroom shall exceed 16 dB above the rated output for all equalization curves.

The unit shall provide a unity-gain 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 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. Controls shall be oriented toward the front edge 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 35 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-LEQ1.