Audio processing: Accessing the Audio Mixer Pipeline

All audio processing in SAM Broadcaster Pro is configured through the Audio Mixer Pipeline:

1. Click the Config button in the toolbar
2. Select Audio Mixer Pipeline

The pipeline shows all inputs: Deck A, Deck B, Sound FX, Aux 1, Voice FX and Mixer. Each has its own processing chain.

Built-In Processing

SAM Broadcaster Pro’s built-in processing includes:

• Equaliser — adjust frequency response across the audio spectrum
• Gated AGC (Automatic Gain Control) — automatically evens out loudness differences between tracks
• Stereo Expander — widens the stereo image
• Bass EQ — boost or cut bass frequencies
• 5-band processor — multiband compressor/expander/limiter for precise control over different frequency ranges
• 2-band processor — simpler two-band alternative
• Clipper — hard limiter to prevent output from exceeding a set level

For most stations, enabling the AGC and setting modest compression values is a good starting point.

DSP Plugins

SAM Broadcaster Pro supports Winamp DSP plugins for additional processing. To add a DSP plugin:

1. Click Config → Audio Mixer Pipeline
2. Open the DSP tab
3. Install your Winamp DSP plugin to the SAM Broadcaster Pro plugins folder
4. Enable the plugin by checking the checkbox next to it
5. Select it and click Configure plugin to adjust its settings

Stereo Tool with SAM Broadcaster Pro

Stereo Tool is a popular third-party audio processor widely used in internet radio. It is available as a Winamp DSP plugin and can be loaded into SAM Broadcaster Pro’s DSP chain. Stereo Tool adds advanced multiband compression, loudness maximising and stereo enhancement beyond what the built-in processing provides.

Processing Guidelines

• Test your processed audio on headphones, phone speakers and a car stereo
• Avoid over-processing — heavy compression causes listener fatigue
• Use the AGC to even out track-to-track level differences before adding heavier processing

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Tuning the Gated AGC

The target level in SAM Broadcaster Pro’s gated AGC sets the average volume for your stream. The attack time determines how quickly the compressor reacts to loud sounds; a faster setting reduces peaks more aggressively.

Conversely, release time controls how fast the gain returns to normal after a loud sound passes. A longer release time prevents sudden drops in volume but might allow noise through. The noise gate stops the AGC from amplifying unwanted hiss and room noise during quiet passages by cutting off low-level signals.

Beginners should start with an attack time of around 5 milliseconds, a release time of about 100 milliseconds, and a target level that feels comfortable for your content. These settings provide a good balance between loudness and clarity without excessive pumping or noise amplification.

Setting Up the 5-Band Processor

The 5-band processor in SAM Broadcaster Pro divides the audio signal into five separate frequency bands at specific crossover points. Each band can be processed independently, allowing for precise control over different parts of the sound spectrum.

Multiband compression ensures that no single part of the mix becomes overly compressed and distorted while others remain too quiet or dynamic. This approach yields a cleaner overall sound compared to applying a single broadband compressor across all frequencies.

However, aggressive settings can lead to audible pumping effects and listener fatigue. It’s best to start with gentle compression ratios and slower attack times before adjusting for more dramatic changes if necessary.

Using the Clipper Safely

The clipper in SAM Broadcaster Pro acts as the final stage of audio processing, ensuring that no signal exceeds a predetermined maximum level. This ceiling value sets an absolute limit on output volume and helps prevent digital clipping.

The clipper catches any short overshoots that might slip past earlier compressors or limiters, safeguarding your stream from unwanted distortion. However, pushing the ceiling too high can introduce harsh distortion artifacts.

It’s recommended to leave a small safety margin below 0 dB FS (full scale) to ensure clean audio and avoid introducing audible distortions. This approach maintains clarity while still achieving desired loudness levels.

Common Processing Mistakes

Over-compression can strip away the natural dynamics of music, removing subtle variations in volume that contribute to its emotional impact. Excessive compression flattens peaks and valleys, creating a monotonous sound lacking in excitement.

Stacking too many processors introduces unwanted artifacts such as phase issues and audible distortion. Each additional processor adds latency and complexity, potentially degrading the overall quality of your audio stream.

Maintaining headroom is crucial to avoid digital clipping and ensure that peaks are managed smoothly without sudden drops in volume or harsh distortions. Checking the sound on various devices like phone speakers and earbuds ensures a consistent listening experience across different playback systems.