Frap Tools Brenso Eurorack Complex Oscillator Module

BRENSO is Frap Tools’ primary analog source of articulated waveforms whose degree of entanglement can be precisely set by the musician.

Its concept developed from a reflection on the very meaning of the word ‘complex,’ which comes from the Latin verb plector, literally meaning ‘to weave.’ The purpose of BRENSO is to update the usual approach to ‘complex oscillator’ by offering many threads to be woven together, rather than a pre-defined weft of controls and waveforms: this to improve clarity, manageability, and to provide more sonic options to the artist.

BRENSO consists of three sections: two for the sound generation (yellow and green), and one for sound processing (white and red).

The generation sections allow control over the two triangle-core oscillators, which can be modulated and synced both internally and externally. The Frequency Modulation can be any combination of exponential and/or linear through-zero.

The processing section is composed of a Timbre Modulation section (white) and a final stage of Amplitude Modulation (red). The Timbre Modulation contains two parallel waveshapers with a PWM circuit, which are mixed with a crossfader and processed by a wavefolder. The wavefolder has symmetry control and can be pinged through a dedicated clock input with a shapeable, nonlinear behavior.

A four-quadrant multiplier further modulates the timbre-modulated sound with the green oscillator’s sine wave: it can perform Amplitude Modulation or Ring Modulation, and a crossfader defines the balance between the modulated and unmodulated signal.

The Timbre section CV inputs are semi-normalled to a Timbre Modulation Bus, which is, in turn, semi-normalled to the green sine wave. Many other modulation destinations are semi-normalled to the other oscillator’s sine wave, with attenuverters and attenuators to guarantee precise control. All the semi-normalizations can be ‘broken’ anywhere throughout the signal routing according to the musician’s needs.

Coarse Frequency Lock
No more tuning issues during a performance!

Every oscillator has a button that locks its coarse frequency to the current value. From this moment on, every twist of the ‘Coarse’ knob will be ineffective (but The Fine knob is still available, from small adjustments on the fly!).

Analog Thru-Zero Triangle Cores
BRENSO’s oscillators are exceptionally stable and provide rich harmonic content. This happens thanks to the two thru-zero triangle cores, which guarantee the most playable behavior and the best response to audio-rate modulation.

You won’t need to find a sweet spot because BRENSO is calibrated to sound ‘as expected’ in any setting!

Linear and/or Exponential FM
Many controls allow for complex and detailed FM sound shaping. It is possible to set the amount of exponential and linear thru-zero FM independently per each oscillator and control their amount of ‘deviation’ through two separate knobs or CV inputs.

(The green oscillator can also work at sub-audio rate, and can therefore become a super complex LFO!)

Four Expanded Modulation Buses
BRENSO’s ‘complex’ signal path is expanded on the front panel and grouped in four ‘modulation buses’: two for modulating frequencies, one for modulating timbre and one for AM and RM.

The green oscillator is always the semi-normalled modulator, but any other source can be used.

Original Timbre Shaping Design
The timbre modulation section has been designed from scratch and offers a versatile blend of two wavefolders, a waveshaper, and a PWM circuit.
A dedicated VCA controls the global amount of modulation to be sent to each modulation section, but the semi-normalization can be broken anytime.

Pluckable Wavefolder
We designed from scratch an analog circuit that, when excited by an external trig, opens the wavefolder above its maximum level and then closes it down with a non-linear slope, whose length can be manually regulated.
This solution can generate percussive tones with a very organic decay.