Input Channel Types
Announcer / Turret Channel
Inputs: The physical source is typically a high-quality dynamic broadcast microphone. Logically, this channel also accepts control inputs from a “Turret” or GPIO controller, receiving signals for physical button presses like “Cough” or “Talkback.”
Outputs: The primary destination is the Program (PGM) bus. However, the signal is often split: when “Talkback” is pressed, the audio is diverted away from PGM and sent specifically to Producer or Director communication busses.
Process: The DSP chain here is specialized for voice intelligibility. It requires a fast-attack Expander/Gate to silence the room between words, and a heavy De-esser to tame sibilance. Crucially, this channel acts as a “Key” or trigger source; its signal is detected to trigger ducking on music channels.
Guest / Panelist Channel
Inputs: These are usually lavalier or tabletop microphones used by temporary guests who may lack microphone discipline.
Outputs: These route to the Program bus but are critical components of the Mix-Minus generation logic, ensuring that while the guest is heard on air, they are subtracted from their own ear feed.
Process: The defining process here is Auto-Mixing (Dugan-style). The channel participates in a gain-sharing algorithm where its level is automatically attenuated if the guest is silent while others are speaking. A hard Limiter is also essential here to catch sudden laughter or coughing fits that could overload the mix.
Playback / Music Bed Channel
Inputs: The input is digital, originating from a playout server or DAW. The source material is often commercial music or pre-produced stings, which may arrive at 44.1kHz or 48kHz.
Outputs: These feed the Program bus and often the Studio Monitor speakers to create vibe in the room. They are rarely sent to Mix-Minus feeds to ensure talent can hear the director clearly without music distraction.
Process: The critical process is Asynchronous Sample Rate Conversion (SRC) to bring the external file up to the console’s 96kHz operating rate. The dynamics section is dominated by Sidechain Ducking, where the compressor listens to the Announcer bus and automatically attenuates the music by 10-15dB whenever the host speaks.
Instrument / Hi-Z Channel
Inputs: These are high-impedance physical inputs designed for electric guitars, basses, or keyboards, bypassing standard mic preamps to preserve high-frequency content.
Outputs: These route to the Program bus and heavily to Foldback/Stage Monitor sends so the musicians can hear themselves.
Process: Processing focuses on tonal shaping rather than corrective repair. This includes Amp Simulation or Saturation to add warmth, and musical, wide-Q Parametric EQ. Unlike speech channels, gates are rarely used here as they can cut off the natural sustain of the instrument.
Ambience / Crowd Channel
Inputs: The source is a stereo pair, or a 5.1/7.1.4 array of shotgun microphones suspended over the audience or stadium.
Outputs: These route strictly to the Program/Surround busses. They are explicitly blocked from routing to Mix-Minus or Talkback busses, as remote talent does not need high-volume crowd noise in their earpieces.
Process: The priority is Uncorrelated Processing. If a stereo crowd feed is summed to mono, phase issues can cause the sound to disappear (cancel out). The DSP ensures phase coherency. No dynamics (compression) are usually applied, as “pumping” crowd noise sounds unnatural.
FX Return Channel
Inputs: This is a virtual input. It receives the “wet” output signal from internal DSP engines like Reverbs, Delays, or Choruses.
Outputs: These route to the Program bus. They are occasionally fed into Stage Monitors if a vocalist wants to hear reverb in their ears.
Process: The processing is minimal to preserve the tail of the effect. The primary tool used is Width/Image Control, ensuring the reverb spreads correctly across the Stereo or Immersive field without cluttering the center channel where dialogue sits.
Upmix / Spatializer Channel
Inputs: The input is a standard Stereo (2.0) signal, often from legacy archives or external feeds that need to match a modern 5.1 or Atmos broadcast.
Outputs: The output is a multi-channel bus (5.1, 7.1, or 7.1.4).
Process: This uses complex Decorrelation and Divergence algorithms. The DSP extracts “dry” center information to route to the Center speaker and “diffuse” information to route to the Surrounds and Heights. It also includes a Crossover filter to synthesize a Low-Frequency Effects (LFE) channel from the stereo bass information.
Downmix / Fold-Down Channel
Inputs: The input is a Surround (5.1) or Immersive (7.1.4) bus.
Outputs: The output is a Stereo (Lo/Ro or Lt/Rt) or Mono signal for legacy transmission or monitoring.
Process: This is a mathematical summing engine. It applies specific Attenuation Coefficients—typically dropping the Center channel by -3dB and Surround channels by -3dB or -6dB before summing them into Left and Right. A True Peak Limiter is applied post-summing to prevent the combined signals from clipping.
Test Tone / Slate Channel
Inputs: The input is an internal signal generator capable of producing Sine waves, Pink Noise, and White Noise.
Outputs: This can route to any destination: Program, Auxes, or Groups, used to verify signal path continuity.
Process: The process involves an Identification Cycle, an automated script that pans the tone to Left, Right, Center, LFE, Left Surround, etc., in a specific order. It may also overlay an audio “Slate” (a voice recording identifying the track) onto the tone.
Output Bus Types
Program (PGM) / Transmission Bus
Inputs: This is the summing point for all active input channels (Announcers, Music, FX, etc.).
Outputs: The physical output feeds the transmission encoder, satellite uplink, or streaming encoder.
Process: The final stage requires Loudness Compliance processing (EBU R128 / A/85) to ensure the integrated loudness hits the target (e.g., -23 or -24 LUFS). A Brickwall True Peak Limiter is the final safety guard to prevent digital overs.
Mix-Minus (N-1) Bus
Inputs: This bus conceptually receives the entire Program mix.
Outputs: The output connects to a telephone hybrid, IP codec, or IFB transmitter feeding a specific remote talent’s earpiece.
Process: The process is a Subtraction Matrix. The system takes the full Program Mix and inverts the phase of the specific talent’s channel assigned to that bus, effectively cancelling them out of the mix so they hear everyone else but themselves.
Foldback / Stage Monitor Bus
Inputs: This receives signals from Input channels, but the “pick-off point” is crucial.
Outputs: The output feeds stage wedges, In-Ear Monitor (IEM) transmitters, or headphone amps.
Process: The send is Pre-Fader, meaning the mix engineer can change the broadcast volume without affecting the musician’s monitor mix. The output bus itself often features a 31-Band Graphic EQ to notch out feedback frequencies.
Control Room (CR) Bus
Inputs: This listens to the Program bus by default, but switches to listen to the “Solo/PFL” bus whenever a Solo button is pressed on any channel.
Outputs: This feeds the Nearfield speakers and Subwoofer in the mixing room.
Process: This bus features Dim Logic, which drops the volume by 20dB when the Talkback button is pressed to prevent feedback. It also includes Bass Management crossovers to split low frequencies to the studio subwoofer.
Direct Out / ISO
Inputs: The signal is tapped directly from an Input Channel’s preamp stage.
Outputs: This connects to a Multi-track Recorder (DAW) or a backup logger.
Process: The goal is Transparency. The signal is tapped before the console’s EQ, Compressor, or Fader affects it. This ensures that the recording is raw and can be re-mixed later if the live broadcast mix had errors.
Talkback Output
Inputs: The input is the Engineer’s dedicated microphone.
Outputs: These are routed to specific communication destinations: Studio Loudspeakers (SA), Producer Intercom, or Remote Truck.
Process: The logic is Momentary / Push-to-Talk. The audio only passes while the button is held. Triggering this process often sends a sidechain control signal to the Control Room monitor to Dim the speakers.
