Upward compression raises low-level audio signals without applying downward peak limiting. However, standard implementations can introduce intermodulation distortion, click artifacts on transients, or amplify unwanted noise floors. To address these limitations, I developed a custom JSFX plugin for REAPER called the Overstratum Simple Upward Compressor. This native audio processor combines a log-domain gain computer, a sample-accurate envelope detector with low-frequency smoothing, and an active peak-protection system to achieve transparent dynamic control.
Just throw it on the Master Bus and listen to what happens!
Core Technical Features
- True Upward Compression: Transparently raises low-level audio signals while leaving louder passages completely unaffected. No downward compression occurs.
- Strict Peak Protection: Features a mathematical gain-clamp that guarantees transients crossing the threshold receive exactly 0 dB of gain, completely preventing clipping or distortion.
- Advanced Envelope Detection: Utilizes a sample-accurate peak tracker with an internal 1ms decay bridge to prevent zipper noise and zero-crossing artifacts on low-frequency material.
- Decoupled Gain Smoothing: Attack and release ballistics are applied directly to the gain computer rather than the audio envelope, resulting in transparent, mastering-grade gain riding.
- Custom Interactive GUI: Features a clean, custom-coded graphical interface with mouse-drag parameter locking (preventing accidental parameter shifts) and a real-time visual Boost Meter.
- Highly Optimized: Native JSFX architecture built for zero latency, click-free operation, and exceptionally low CPU consumption. Supports both mono and stereo processing.
Parameter Controls
- Threshold (dB): Determines the level below which upward compression engages (-60 dB to 0 dB).
- Ratio: Sets the intensity of the upward gain curve (1:1 to 10:1).
- Max Boost (dB): A crucial safety ceiling that limits the maximum amount of gain applied to deep silence or noise floors (0 dB to +24 dB).
- Attack (ms): Controls how quickly the compressor reacts and applies gain when the signal falls below the threshold (0.1 ms to 200 ms).
- Release (ms): Dictates how fast the compressor removes the applied gain to get out of the way of an incoming loud transient (5 ms to 1000 ms).
- Output Gain (dB): Linear output level adjustment for final gain matching (-24 dB to +24 dB).
- Mix (%): Built-in dry/wet balance control for easy parallel processing (0% to 100%).
- Bypass: Instantly toggles the audio processing on or off.
You can find the free download here: JSFX Tools