ST-HP3 Line-Level High Pass Filter
The line-level high-pass filter shall be an RDL ST-HP3. The unit shall provide one line-level input and two line-level outputs. Each output shall be filtered to attenuate low frequencies and shall be identified by the lowest frequency it passes nominally flat.  One output shall be designated the 500 Hz output, the other the 300 Hz output.

The input shall be electronic balanced bridging with a nominal input impedance of 20 kOhms and shall be fully compatible with either an unbalanced or balanced line-level audio source. The unit shall provide fixed gain at unfiltered frequencies of 0 dB (+0 dB / -2 dB).

Each output shall be filtered to attenuate low frequencies at a slope of 18 dB per octave. The designated 300 Hz output shall have a frequency response of 300 to 30 kHz (± 0.5 dB) with a -3 dB frequency of 225 Hz.  The designated 500 Hz output shall have a frequency response of 500 to 30 kHz (± 1 dB) with a -3 dB frequency of 450 Hz.  The unit shall employ active filtering.

The unit shall provide both line-level balanced audio outputs 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 minimum input and output headroom of 18 dB above +4 dBu with THD+N less than 0.01% and residual noise more than 90 dB below +4 dBu.

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.

Power requirements shall be 24 Vdc ground-referenced with a maximum current not exceeding 30 mA.  The unit shall utilize an external power supply and shall be equipped to operate from 24 Vdc ground-referenced or bipolar ± 12 Vdc or ± 15 Vdc power. 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-HP3.