UVI Focus

Deep Dive

The R&D behind UVI effects

UVI has a long history of research and development in effects plugins. For over 10 years, our development team has worked to offer the most accessible products at the cutting-edge of audio processing. The recent release of “The Effects Bundle” marks a perfect occasion to look at how our team has designed three of the most iconic effects of our collection: Opal, Drum Replacer, and Plate.

OPAL

Opal is our brand-new optical program-adaptive leveler, designed to emulate a beloved vintage optical compressor from the ‘60s. We spent more than a year on research and development to create an emulation based on a physical model of the original circuit design. Opal reproduces the inherent program-dependent response times and nonlinearities which contribute to this famous compressor’s sonic signature.

The circuit

The circuit schematic was thoroughly analyzed stage-by-stage, including: gain reduction, sidechain and make-up circuit. As it contains about 40 electronic components, a brute force simulation would be too CPU-intensive for real-time use. Fortunately, some simplifications were possible without affecting the overall sound. In particular, we found we could differentiate between actual features of the circuit, and what mostly reflects hardware design constraints of the time, which we could then work around in a virtual analog model. Some stages were decoupled, some components were lumped together, and some components were forwent altogether.

The measurements

Next we performed measurements on several optical compressors to extract the characteristics of their optical cells, namely the photoresistor’s internal dynamics, and the law for the optical coupling between the photoresistor and the light-emitting element. As these were real machines used in real studios, the measurements had to be as non-intrusive as possible, meaning no circuit dismantling to measure components in isolation. Knowing the rest of the circuit’s electronics already, we could do some reverse engineering and estimate our model’s parameters for the optical cell with a bit of machine learning, based on these measurements.

The integration

For the simulation itself, we applied some reduction and pre-resolution techniques, and were able to reduce the model to 2 x 4th order systems (out of 40 components to begin with). The solver was also specially designed to be computationally efficient. Finally, we added modern features including external sidechain, variable responsiveness, frequency response correction, and tube drive, to create our own innovative physical model.

DRUM REPLACER

For Drum Replacer, we wanted to create a drum replacement tool, simple on the surface and easy to use, keeping the well established metaphor of level-based trigger detection. But under the hood, we spent time on a number of advanced signal cleaning and pre-processing methods, such as source separation and machine-learning methods to simplify the detection task.

Drum separation

Our rationale regarding drum source separation was as follows: rather than training an average model on big datasets, we decided to use the most available information with local ad hoc drum models tailored to each specific drum recording situation. In most multi-mic drum set recordings there is a dominant drum kit element per microphone, sometimes polluted by bleed from other drumset elements. Using blind source separation methods, it is then possible to learn ad hoc models of the dominant drum layers, and then isolate and resynthesize only the main drum element we are interested in, simply by listening and toggling the different components.

Since signal is additively resynthesized in a constructivist manner, background bleed elements (e.g. hi-hats on a kick drum track) or noise can be efficiently removed. Combining these tools, borrowed from academia, provides a way to address difficult use cases by making the most of the available information about the problem at hand.

PLATE

One of our main goals for Plate, was to have a fully parametric plate reverb to be used creatively, by letting people design their own custom plate reverb way beyond what's possible in reality. Plate employs realtime physical-modeling with up to 20,000 modes to achieve new levels of depth and detail, going well beyond the limitation of physical units.

Physical modeling in action

The most iconic plate reverb, the EMT140, is a heavy device made of a large sheet of steel measuring 2m x 1m, with fixed transducers attached to the metal, and foam to control the amount of damping.

In contrast, thanks to physical modeling, Plate allows us to change:

• Physical dimensions for example a thin and long plate will sound similar to a spring reverb with very dispersive wave propagation of pulses like in railway
• Material, to change propagation speed and inharmonicity
• Tension, to control modal frequencies tuning
• Transducer placement, to change the reverb timbre

All kinds of damping are based on academic research and physically grounded, but we also made sure that one can play, extrapolate, and mix them intuitively in an easy-to-use interface with just a few clicks.

We even included some out-of-this-world features, like mode modulation in order to bring the lush chorused tails of algorithmic reverbs into the world of physical modeling.

We wanted Plate to be an authentic and accurate emulation. For that purpose, we went to a famous studio in Paris to perform in depth measurements on the well known EMT140 (steel) and EMT240 (gold foil). We then spent time calibrating the physical model to closely match our measurements for all kinds of settings.

We even included some out-of-this-world features, like mode modulation in order to bring the lush chorused tails of algorithmic reverbs into the world of physical modeling. We wanted Plate to be an authentic and accurate emulation. For that purpose, we went to a famous studio in Paris to perform in depth measurements on the well known EMT140 (steel) and EMT240 (gold foil). We then spent time calibrating the physical model to closely match our measurements for all kinds of settings.

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