The Heil Parametric Receive Audio System (PRAS) is a state-of-the-art audio system that enhances the internal audio systems of amateur radio, shortwave, commercial, and CB receivers. The PRAS allows radio operators to modify, shape, and
improve the audio output of their receivers using three separate equalization controls.

Midrange frequencies are the most critical for achieving clear voice articulation in receive audio. The Parametric Receive Audio System allows operators to have unique control over these important frequencies. First, operators can adjust
the parametric midrange filter from 400 Hz through 4 kHz, with the recommended sweet spot being at 2.5 kHz. In addition, operators can control the presence of these midrange frequencies plus or minus 15 dB. Combined with a low-frequency
filter down to 160 Hz, and a high-frequency filter up to 6 kHz, the Parametric Receive System provides operators unparalleled control and quality of their receive audio.

The PRAS has three audio inputs: standard XLR and 1/8" inputs, and an 8 ohm input that can be used with the 8 ohm speaker output of any receiver.

There are three audio outputs on the PRAS: balanced XLR and 1/4" outputs on the rear panel, and a 1/8" output on the front panel for recording audio. The PRAS also has two built-in headphone amplifiers with separate level controls and dual
1/8" headphone outputs.
The PRAS is intended to be used with the Heil HPS-5 powered speaker (the PRAS must be used with a powered speaker).