Entangled Sound Sources

brenso /ˈbreːnso/ adj. [slang portmanteau word created from the Italian adjectives breve ‘short’ and intenso ‘intense,’ probably around the early 2000s in the area of Bologna; pronounced with the long, closed e instead of the expected open ɛ, as typical of the Northern Italian regions] — This adjective may have originally referred to events or experiences that were particularly powerful despite their short duration. Soon its meaning broadened, indicating anything (objects or even thoughts) that feature great content in proportion to the size. For example, nowadays, a thick lasagna or a massive live performance can be equally ‘brense.’




550,00  + VAT

In stock


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 oscillators by offering many threads to be woven together, rather than a pre-defined weft of controls and waveforms: this to improve clarity, manageability, and provide more sonic options to the artist.

BRENSO consists of three sections: two for 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.

Key Features

BRENSO brings to the surface all the ways of shaping your sound: frequency modulation, amplitude modulation, and timbre controls.

Both oscillators have their independent FM modulation circuit.

The yellow oscillator, then, feeds a Timbre Modulation section which, in turns, can be blended with its amplitude- or ring-modulated copy.

We designed the timbre modulation section from scratch with two wavefolders, a waveshaper, and a PWM circuit.

A dedicated VCA controls the global amount of modulation to each parameter section. The green oscillator is the default modulator, but you can override the semi-normalization anytime.

Many controls allow for complex and detailed FM sound shaping. It is possible to set exponential and linear thru-zero FM independently per each oscillator and control the FM 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!)

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!).

BRENSO’s oscillators feature thru-zero triangle cores, which guarantee exceptional tracking and the best response to audio-rate modulation.

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

The green oscillator has four outputs: sine, triangle, square, and sawtooth.

The yellow one has four outputs: sine and triangle as well, then a selectable square/shaped square output, and a Final output for the triangle wave after its routing through the Timbre and Amplitude Modulation sections.

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.

You can sync the green oscillator to the yellow one in two ways.

The Lock Sync removes any unwanted beating and preserves tracking.

The Flip Sync reverts the synchronized oscillator’s direction to the rising edge. It is similar to the classic Hard Sync but without forced restarts and sudden “pops” like in sawtooth-core oscillators.




Additional information

Weight 0,57 kg
Dimensions 15,6 × 23,6 × 6 cm



30 HP


38 mm

Current draw

325 mA @ +12 V

235 mA @ -12 V

Recommended warmup time

30 min

V/oct input impedance

> 90 KΩ

FM source input impedance

> 30 KΩ

Deviation CV input impedance

> 90 KΩ

Integrator CV input impedance

> 40 KΩ

Sync input impedance

> 60 KΩ

Sync input minimum amplitude

2 Vpp

Sync input suggested amplitude

±5 Vpp

AM CV input impedance

> 40 KΩ

AM source impedance

> 90 KΩ

AM source suggested amplitude

±5 Vpp

Modulation bus source input impedance

> 40 KΩ

Modulation bus CV input impedance

> 90 KΩ

Triangle waveshaper CV input impedance

> 60 KΩ

Pulse waveshaper CV input impedance

> 60 KΩ

PWM CV input impedance

> 90 KΩ

Wavefolder Source CV input impedance

> 25 KΩ

Wavefolder CV input impedance

> 60 KΩ

Wavefolder Symmetry CV input impedance

> 50 KΩ

Ping input impedance

> 90 KΩ

Audio output impedance

> 100 Ω

Audio output amplitude

±5 V

Coarse frequency knob range (audio rate)

27.5 Hz to 7040 Hz

Coarse frequency knob range (LFO)

LFO ratio


Oscillator tracking

±5 ȼ

Oscillator fine tuning

> 1 st

Oscillator core crosstalk

-50 dB

More details on the Manualone.


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A. Use

Our modules are packed with high-quality components that demand a proper power supply and can get sensibly warm.

That is its normal temperature and we can guarantee their performance.

The timbre section is part of the sound generation and we designed the signal path to derive its waveforms straight from the oscillator’s core, so no, it is not meant to be used with external signals.

B. Design

We have two main kinds of capacitors.

The first one is necessary to AC-couple the audio signal: they prevent any unwanted DC offset, and they offer protection against wrong connections. For this reason, you can patch nearly every input to every output, and the worst thing that can happen is some pops or some silence.

The second one is power filters to guarantee a cleaner current flow across the case. They might sound a bit over the top, but we must remember that a Eurorack system is not something that comes straight out of the factory. Instead, every Eurorack setup is unique and may change according to the musician’s need. For this reason, we want to add as much protection as we can, both to avoid issues with our modules and to ensure that even the other modules behave correctly. We use a wide mix of capacitors in our modules: ceramic, electrolytic, tantalum, and multilayer. They can be assembled thru-hole or SMD, according to what gives the best balance between result and space. For example, all the electrolytic capacitors are mounted thru-hole because they perform better according to our tests.

However, the capacitors have zero impact on the power draw, on which you can read in this other FAQ.

Power draw should always be related to what a module does.

Generally speaking, there are modules like SAPÈL that undoubtedly consume more than other random generators. However, SAPÈL is a double module, so a fair comparison would be between it and a pair of similar modules. The same can be said for FUMANA, the most power-demanding filter bank. However, it is also the only Eurorack filter bank with 32 analog bandpass filters, half of which have a 48 dB/oct slope. So, also in this case, a fairer comparison would be between FUMANA and TWO other 16-band filter banks, which leads to similar power consumptions.

More in detail, we engineer our modules to be safe to use. To protect both the modules and the rest of the case, we add a proper buffering stage to every input and output: even if a single buffer doesn’t draw that much power, all the ins and outs piled together can significantly impact the final power draw.

The higher oscillator crosstalk recorded is -50dB at higher frequencies, where it can be more noticeable.

BRENSO uses a microcontroller to perform the digital sample-and-hold that we use for the Coarse Frequency Lock. When you push the button, the circuit will sample the frequency value and hold it until you push it again.

C. Shop

Yes! We opened our online store in October 2022. Check out the full catalog!

Our resellers receive our modules exclusively through our distributor, so we do not have access to the individual shops’ orders or stocks.

We restock every module at least once over a year: we focus on a module’s batch at a time, then we move on to the next one, and so on.

If you want an estimated delivery time for a specific module, drop us a line! We’ll be happy to answer you.