United Plugins has released the modulation plugin DuoFlux. SounDevice Digital, the developer of this plug-in, previously released a reverb with a similar concept called Biverb. While Biverb created an interesting sense of space with dual reverb, DuoFlux extends that principle into the realm of modulation. While adopting the same interface design and signal splitting method, SounDevice Digital appears to be expanding its product line into one series.
The most core feature of DuoFlux is how it divides the audio signal into four modes. The large knob in the center allows you to select frequency (Low/High), volume (Quiet/Loud), stereo (Left/Right), or Mid/Side. In particular, volume-based signal splitting allows different effects to be applied to quiet and loud sections, opening up new possibilities for dynamic sound design.
The left and right units can each select from 17 modulation algorithms, and detailed parameter control is possible with the Depth, Rate, Width, Feed, and Character knobs. The LFO Shape control can be continuously changed from a sine wave to a sawtooth wave or a square wave by dragging, and the waveform can also be reversed with the Invert function. The same as Biverb, each unit has built-in high-pass and low-pass filters.
The best thing about this method is that you can operate two processors on one screen without complicated routing. Splitting the left and right channels can be easily accomplished without these plug-ins, but mid/side work can become a bit complicated. A separate plug-in is required to create different effects due to differences in frequency or volume.
However, as mentioned in the Biverb review, it is difficult to say that the sound quality of the individual effects or the algorithm itself is the best. It is difficult to directly compare it to professional chorus plug-ins that cost hundreds of thousands of won. The value of DuoFlux lies in creativity rather than the absolute quality of individual effects.
It’s quite effective in creating a vintage texture. Each unit includes a Tape section, which adds an analog sensibility to digital sound with saturation, wah, flutter, and noise. (However, the Noise parameter may feel a bit excessive, so caution is required.) Modulation algorithms such as vintage-type chorus and rotary are also attractive.
The two interfaces, arranged symmetrically left and right, are visually clear. The user experience is not unfriendly, but the many knobs can leave a somewhat confusing impression to beginners. If you are not a producer with a clear perspective, you may be confused about how to change the left and right interfaces. In this case, well-made presets are a good starting point for understanding the mechanism of the plug-in, but the presets built into DuoFlux feel a bit lacking in variety and number.
If you’re creative, you can experiment with this plugin in many ways. Applying different modulation to the left and right is basic, and you can also adjust the movement speed of the low and high frequencies in the pad sound differently. You can have a low-cut oobbler effect only on the side channels, or a slight tape saturation and rotary effect only in the high-volume areas.
If you think about a real-world usage scenario, you could apply frequency-based splitting to a synth pad, with a slow phaser in the low range and a fast flanger in the high range, creating complex yet harmonious movements. If you use Mid/Side mode on an acoustic instrument, you can add a sense of space to the sides while maintaining the direct sound in the center clearly. Volume-based segmentation presents interesting possibilities for vocal processing. You can give different characters depending on the dynamics, such as adding subtle modulation to quiet breathing or weak sections and a more dynamic effect to strong sections.
The top toolbar has convenient A/B comparison functions and undo/redo buttons, and an 8x oversampling option is also provided. In the right-mouse button menu, you can also make detailed settings such as adjusting the GUI size, GPU acceleration, and power saving functions during silence.
It supports both Windows and Mac and is compatible with most DAWs in VST, AAX, and AU formats. The regular price is 79 euros, but you can purchase it for 15 euros as a launch promotion until the end of February 2026. A 15-day free trial is also available so you can test it out for yourself.
