as_fbComp: Feedback Compression with Sidechain Intelligence
In the world of audio processing, compression holds a central position. It not only helps control the dynamic range but also significantly impacts the character and “feel” of a track. Among the various types of compressors, those that use the principle of feedback stand out. This approach is implemented in the as_fbComp plugin from developer antto. This plugin offers a unique combination of classic feedback compression, flexible sidechain, and additional tools to give your sound a special warmth and control.
as_fbComp is not just another compressor. Its architecture, based on a feedback loop, allows for a more musical and organic response to the input signal compared to traditional “forward” compressors. This makes it an excellent choice for processing vocals, bass, drums, or even entire mixes, where a dynamic and “breathing” sound is needed.
Key Features of as_fbComp
The plugin is packed with features that make it a versatile tool in your arsenal:
- Feedback Compressor/Limiter: The main strength of the plugin lies in its feedback architecture, which gives the compression a natural, musical character. It can work as a soft compressor or an aggressive limiter.
- Sidechain Capabilities: The built-in sidechain allows you to use an external signal to control the compression. This is ideal for the classic “pumping” between kick and bass or for other creative effects.
- Operating Modes: The plugin offers two main modes:
MONO Mode
In this mode, the left channel is used as the main audio input, and the right channel is used as the sidechain input. This is extremely convenient if your DAW allows routing different signals into the left and right channels of a single stereo track. In MONO mode, a unique function for balancing the sidechain source signal (“Source” knob) is also available. You can mix the processed signal itself (L) and the external sidechain signal (R) for the compression detector, finding the perfect balance to activate the compression. This mode is also more CPU-optimized.
STEREO Mode
Standard stereo mode, where both channels are processed together, reacting to the overall level of the stereo signal. Simple and effective for processing stereo tracks or mixes.
- Side-Chain Filter: The plugin has a simple but effective LowShelf filter in the sidechain. Its frequency is adjustable from ~16 to ~160 Hz, and the gain/attenuation is from -1 to +4. A value of -1 actually creates a high-pass filter (HPF), which allows you to ignore low frequencies in the sidechain and avoid excessive “pumping” from the low end. Positive values (+4) can, conversely, emphasize low frequencies in the sidechain for a more pronounced reaction to the kick drum.
- Output Saturation: The output signal passes through a light, asymmetric shaper that gently limits the level to 0dBFS. This adds a pleasant analog warmth and helps control peaks, regardless of the dynamics after compression.
- DC-Filtering: DC filtering at the input and output ensures a clean signal without unwanted shifts.
- Dry Knob: The “Dry” knob allows you to mix the unprocessed (dry) signal into the compressed output. This is the implementation of parallel compression directly inside the plugin, which makes it possible to get a dense, controlled sound while preserving the natural attack and dynamics of the original.
- Oversampling and Delay: as_fbComp works with 4x internal oversampling, using high-quality windowed-sinc filters. This provides high processing quality and minimizes digital artifacts (aliasing), especially when using saturation or aggressive settings. It’s important to know that oversampling introduces a small delay, which is not reported to the host.
- Smooth Parameter Adjustment: The INPUT, OUTPUT, and DRY parameters have smoothing to prevent abrupt volume jumps when changing them during playback.
Despite its free nature, as_fbComp offers features and sound quality that can compete with commercial plugins. Its unique feedback architecture, combined with a flexible sidechain, makes it a valuable tool for both subtle dynamic control and bold sound shaping. If you are working in a Windows (32-bit) environment and are looking for a compressor with character and advanced sidechain capabilities, as_fbComp deserves your attention.
