Digital Stage Box Product

Overview

A digital stage box is a networked audio interface that consolidates multi-channel microphone inputs at the point of use (a stage or outdoor broadcast location) and transmits them digitally over a single ethernet cable to a mixing console located in the FOH (front-of-house) position or broadcast truck. The device replaces miles of analog microphone cable with a single gigabit ethernet link, dramatically simplifying cable runs while reducing interference and ground loop problems. The Preamp Card Array provide studio-grade phantom-powered preamplification with individual gain and pad controls, while the AD Converter Bank digitizes all channels simultaneously via 24-bit conversion. The Dante Network Processor embeds Dante protocol (AES-67), allowing the stage box to appear as a network audio endpoint on a professional console's I/O matrix.

How it Works

Distributed Analog and Digital Architecture

Analog microphones connected to the stage box's Connector Panel Assembly XLR jacks feed eight identical Preamp Card Array. Each card includes:

1. Input Isolation Transformer: Provides galvanic isolation and impedance matching.
2. Preamp Operational Amplifier: Low-noise operational amplifier delivering 0–70 dB continuously variable gain.
3. Pad Switch: Optional -20 dB attenuation for hot instruments or wireless packs.
4. Phantom Power Relay: Supplies 48 V to XLR pins 2 and 3 (selectable per channel).

This hybrid approach allows local gain adjustment and phantom control without requiring the mixing console to be present on stage. A field engineer can verify microphone health and adjust levels before FOH personnel receive the signal.

Simultaneous Analog-to-Digital Conversion

All eight channels feed a single AD Converter Bank that performs simultaneous 24-bit ADC at up to 96 kHz sample rate. This synchronous capture ensures that all microphones are sampled at the same instant—critical for phase alignment in surround or Ambisonics field recording. The ADC's Master Clock Reference master clock provides timing reference accurate to ±20 ppm, sufficient for professional broadcast standards.

Dante Network Transport

The Dante Network Processor FPGA runs the Dante protocol, a proprietary audio-over-ethernet standard developed by Audinate. Dante carries uncompressed audio in deterministic, real-time fashion: eight channels of 24-bit audio at 96 kHz require approximately 13 Mbps throughput (well below gigabit capacity). The protocol includes:

• Dante flow control: Negotiates bandwidth and latency with network switches.
• Clock recovery: Extracts sample-rate timing from network packets, maintaining audio synchronization without relying on console timing.
• Redundancy: Ring topology via the Dual Dante Ethernet Interface dual RJ45 jacks allows one cable break without losing signal.

Network Connectivity

The stage box connects to the console via a single RJ45 cable running over the tour's network—potentially several hundred feet away. An optional battery backup (Battery Module) on the Redundant Power Module ensures the stage box continues transmitting audio even if venue power is interrupted (critical for backup generators during rolling blackouts).

Local User Interface

The Local Control and Display LCD and encoder knob allow a field technician to:

• Verify which channels have phantom power enabled.
• Check peak levels per channel.
• Confirm network connectivity and sample rate.
• Monitor temperature and supply voltage status.

Without this local UI, troubleshooting would require a laptop physically present on stage.

Fallback Modes

Some professional stage boxes include an optional direct analog output (Fallback Audio Output) that bypasses the network entirely. If the FOH console loses network connectivity to the stage box, the engineer can patch the analog output directly into a console backup channel, ensuring show continuity.

Live Sound Workflow

In a large concert:

1. Setup: Stage box is positioned on a stage platform near talent. Eight microphones feed XLR inputs; dual ethernet cables run to FOH mixing console in the house.

2. Soundcheck: A technician on stage adjusts each preamp card's gain using the rotary knob. Phantom power is toggled on for condenser microphones. Pad switches are enabled for hot instruments.

3. Show run: The mixing console FOH engineer receives all eight channels as a virtual network endpoint. Faders, EQ, and effects are applied at the console—the stage box is essentially invisible, acting only as a transparent I/O device.

4. Emergency: If network fails, analog fallback output connects directly to a console backup channel, allowing the show to continue.

Studio Recording and Broadcast

Digital stage boxes are increasingly deployed in classical recording, live broadcast, and multi-camera film shoots. A 32-channel stage box connected via ethernet to a control room recorder eliminates analog cable runs across a large venue, each run being a potential RF pickup point. The deterministic latency (<2 ms) allows synchronized recording of reference audio alongside video camera inputs, simplifying post-production sync.

Network Architecture Considerations

Dante flows over standard gigabit ethernet but requires carefully configured switches to maintain deterministic delivery. A professional Dante network uses managed switches with VLAN and QoS prioritization, ensuring audio packets are never delayed or dropped even if the network is carrying heavy internet traffic. Consumer ethernet switches are insufficient—a single high-bandwidth file transfer can cause audio dropouts.

Redundant network topology (ring) is critical for touring: if a single cable is severed during load-out, a properly configured ring automatically routes audio through the alternate path without interruption. Non-redundant linear topology (point-to-point) fails completely on cable breakage.

Specifications and Standards

Dante is owned and maintained by Audinate and is royalty-bearing to equipment manufacturers. Competing standards include AES-67 (an open standard that Dante is compatible with) and Ravenna (a proprietary system used in some European broadcast environments). Most modern consoles support multiple standards simultaneously, allowing a stage box to interoperate with different networking equipment.

The 24-bit resolution preserves the full dynamic range of professional microphones (approximately 130 dB SPL maximum, 20 µPa minimum audible, = roughly 140 dB SNR). The 96 kHz sample rate accommodates HF extension for specialized applications (ultrasonic field recording, artifact-free capture of high-impedance instruments).