Symetrix 425 - Architects and Engineers Specification; Unit Description

Appendix A. Architects and Engineers Specification
The Compressor/Limiter/Expander shall be a dual channel model that controls the dynamic
range of wide range, wideband audio signals, providing compression, peak limiting, and
downward expansion simultaneously. The unit shall occupy one rack space (1U).
The threshold of the compressor section shall be adjustable over a range of -40dBu to
+20dBu via a front panel control. When the control is fully clockwise the section shall revert
to bypass mode. The input-to-output ratio (compression ratio) shall be adjustable from 1:1 to
10:1. Control of the compressor release time shall be program dependent within a range set
by the front panel release time control. The compressor section shall have a dedicated eight
segment LED ladder that displays the degree of gain reduction.
The Compressor/Limiter/Expander shall contain an integral peak limiter having a 20:1
compression ratio and adjustable threshold level. A dedicated four segment LED ladder shall
be provided to indicate the amount of peak limiter activity.
A front panel switch, with LED indicator, shall select between dual mono and stereo
master/slave operation. Each channel shall have a bypass switch which defeats all front
panel controls for that channel.
The Compressor/Limiter/Expander shall also contain a downward expander having a 1:1.5
expansion ratio with threshold, and release time controls. A dedicated four LED display shall
be provided to indicate the amount of downward expansion.
The inputs shall be active balanced bridging designs terminated with 3-pin XLR (AES/IEC
standard wiring), and 1/4" TRS female. The input circuitry shall incorporate RFI filters. The
outputs shall be active balanced designs having equal source impedances and terminated with
3-pin XLR (AES/IEC standard wiring), and 1/4" TRS female.
The balanced inputs shall accommodate +20 dBu signals without distortion, and the balanced
outputs shall be capable of delivering +23 dBm into a 600 ohm load.
Overall frequency response shall be 10 Hz - 60 kHz (+0dB, -3dB). THD shall be .02%
measured under the following conditions: +4 dBu input, +18 dBu output, BYPASS switch out,
20 Hz to 30kHz, 30kHz low-pass filter, 0dB gain reduction. Residual noise output shall be no
greater than -90 dBu, measured with a 20 kHz noise bandwidth, input terminated in 600
ohms.
Access to each channel's sidechain shall be provided via a single 1/4" TRS female connector
(per channel). The ring connection shall be the sidechain output and the tip connection shall
be the sidechain return.
The unit shall be capable of operating by means of its own built-in power supply connected to
117V nominal AC (105-130V) 50/60 Hz (230V nominal, 207-253V AC, 50 Hz where
applicable).
The unit shall be a Symetrix Incorporated model 425 Dual Compressor/Limiter/Expander.
A-1
Rev 2.0, 10/29/93