Avid Stage Rack
Eighty-six pounds of remote I/O that turned a snake cable into a network connection - the box that made the monitor world disappear from front of house.
Overview
The Stage Rack is the remote I/O half of Avid's VENUE live sound platform. It sits on stage and does the actual work of converting the world into ones and zeros. It is a 10U steel rack unit measuring 17.5 x 17.0 x 12.2 inches (445 x 432 x 310 mm) and weighing 86 lbs (39 kg). That stops being abstract the first time two people have to lift one onto a riser at load-in. Inside, it holds up to twelve I/O card slots, six input and six output, for a maximum of 48 inputs and 48 outputs in a single rack.
The Stage Rack is interesting for what it doesn't do. It doesn't pass analog audio down a copper multicore to front of house. It digitizes at the source and ships the signal to the FOH Rack over dual redundant 75-ohm BNC digital snakes, which are not included. Keep that in mind before buying a used one, because the snake is a meaningful part of the system cost and a rack without one can't actually be used. A 250 ft (76 m) run with Belden 1855A, or 500 ft (152 m) with Belden 1694A, carries the same signal integrity as a short cable run. No ground loops, no high-frequency rolloff over a long copper snake, no transformer isolation boxes at the split.
The base configuration ships with six SRI (Stage Rack Analog Input) cards and one SRO (Stage Rack Analog Output) card, along with two AC power cords. That's 48 mic/line inputs and 8 line outputs out of the box. The input side is already maxed, but the output side is expandable to 48 with optional output cards. The architecture is modular: any combination of analog and digital inputs, analog and digital outputs, and A-Net outputs can be fitted, up to 48 total in a single rack. For larger productions, two Stage Racks can be connected to a single FOH Rack for a total of 96 mic/line inputs and outputs.
The SRI input card is where the spec sheet gets serious. Each card carries eight XLR3-Female connectors with +48V phantom power, individually switchable per channel via software. Gain runs from +10 dB to +60 dB in 6 dB analog steps with 0.1 dB digital increments and a crossfade at the analog relay switch point. That gives an analog-style gain stage with digital precision. Maximum input level is +34 dBu with the 20 dB pad engaged. Input impedance is 10 kOhm balanced with the pad off, dropping to 4 kOhm with the pad on. Equivalent input noise is specified at -126 dBu maximum gain with a 150-ohm source across a 22 Hz-20 kHz bandwidth, unweighted. That's a quiet mic preamp, and it's the number that separates this from the budget digital stage boxes that came later. THD+N is 0.003% at minimum gain, pad off, -1 dBFS output. The A/D converters are 24-bit delta sigma with 0.25 ms latency at 48 kHz.
The SRO output card carries eight XLR3-Male connectors with 50-ohm output impedance and a maximum output level of +24 dBu. The D/A conversion is 24-bit delta sigma with 128x oversampling and 0.58 ms latency at 48 kHz. Signal presence LEDs on both card types illuminate at -37 dBu or greater. Power requirements are 90-260 VAC, 50-60 Hz, drawing 140 W. The unit comes standard with dual redundant, field-replaceable power supplies, so if one fails mid-show the other keeps the band audible.
A PQ Link connector (XLR4-M) allows connection to a PQ Rack over 110-ohm digital cable, with a maximum cable length of 15 ft (4.6 m). That's short because it's a local link rather than a long-haul run.
The Stage Rack was designed as the remote I/O component of both the D-Show and Profile systems. Front-of-house engineers who worked these systems in the field were vocal about the workflow.
The documentation for the Stage Rack carries a Digidesign address in Daly City, California, and a copyright date of 2009 from Avid Technology, with the part number 9321-61361-00 REV A dated 04/09. That places the manual in the period after Avid had absorbed Digidesign branding into its own, but the D-Show and Profile names are still present throughout. The VENUE line was still being documented under both names.
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