ST-CL2 Line-Level Compressor/Limiter
The compressor/limiter unit shall be an RDL ST-CL2. The unit shall provide one balanced line-level audio input. The unit shall compress the input signal according to three automatically-adjusting timing circuits to drive a balanced line-level output.  A user input gain control shall be provided to set the amount of compression for normal input levels. Adjustment of the unit shall be possible using provided LEDs that indicate the amount of compression. The unit shall incorporate instantaneous soft peak limiting. A user output level control shall be provided to set the output level. The unit shall be equipped for stereo interconnection to a second like unit.

The input shall be electronic balanced bridging with a nominal input impedance of 10 kOhms and shall be fully compatible with either an unbalanced or balanced line-level audio source. The input shall provide common mode rejection greater than 60 dB from 50 Hz to 120 Hz. The unit shall provide normal operation of up to 6 dB gain reduction for input signal levels from -10 dBu to +4 dBu.  The input shall be capable of input signal levels up to +22 dBu without clipping. 

A continuously adjustable multi-turn trimming control shall be provided to set the fixed gain of the input stage. Two LEDs shall be provided to set the input gain.  A yellow LED shall vary in intensity in proportion to normal compression levels.  A red LED shall vary in intensity in proportion to heavy compression.  

The unit shall provide audio compression based on internal detectors feeding three timing circuits. The threshold level and slope of each timing circuit shall be incremented to respond sequentially to signals of varying amplitude and energy levels. The unit shall provide a soft-knee compression threshold and compression ratio that automatically adjust to the program material. The unit shall include an averaging compressor with a 500 ms response time for a +4 dBu input and a fast compressor with an attack time faster than 10 ms for a +20 dBu input.  Peak limiting shall be instantaneous.  The compressor release time shall automatically adjust up to 500 ms. The compression ratio shall automatically adjust from 1.5:1 to 10:1.

The unit shall provide audio frequency response of 10 Hz to 20 kHz (± 0.2 dB) a noise floor exceeding 78 dB below an output level of +4 dBu.  Total harmonic distortion shall be less than 0.05% below the compression threshold at 1 kHz, less than 0.1% with 3 dB gain reduction at 1 kHz and less than 0.15% with 6 dB gain reduction at 1 kHz.

The unit shall provide wiring terminals for stereo compliance coupling to a second ST-CL2.

The unit shall provide one line-level balanced audio output at a nominal rated output level of +4 dBu with an output impedance of 150 O. A continuously adjustable multi-turn trimming control shall be provided to set the output level from off to +8 dBu.  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. Indicators and 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.

The unit shall be equipped to operate from either 24 Vdc ground-referenced power or from bipolar ± 12 Vdc or ± 15 Vdc power with a maximum current not exceeding 50 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-CL2.