Tamed Random Source

sapèl / saˈpɛːl / s.m. [dialect from the northern area of Modena – Italy, uncertain etymology: probably from vulgar Latin sappa, ‘hoe’, meaning ‘roughly hoed’] – ‘mess’, ‘muddle’, ‘chaos’.


38 mm deep

250mA +12V   –   170mA -12V


The SAPÈL is a random control voltages source for Eurorack modular systems. It is composed of two main sections, one that generates audio noises, in 4 different versions, and another which includes two specular random clock, random voltages, and clock sources.

Noise outputs are color coded, based on the noise colors, and include:

  • blue (+3dB/oct spectrum)
  • white noise (0dB/oct spectrum)
  • pink noise (-3dB/oct spectrum)
  • red noise, a.k.a. brown or brownian (-6dB/oct spectrum).

The random voltage and clock section features four uncorrelated random CV generation paths, divided in;

  • fluctuating random voltage;
  • quantized random voltage with 2n stages tuned in semitones referred to 1V/oct scale;
  • quantized random voltage with n+1 stages tuned in octaves referred to 1V/oct scale;
  • non-quantized sample & hold.

It is also possible to set a probability distribution with a potentiometer, and apply (or do not apply) the chosen distribution setting to each of the four paths independently.

Furthermore, each of the two random sources section features an independent built-in clock generator, with clock output and random clock output, which can be used in “more than” or “less than” mode. It is possible to use an external clock signal as a clock source, bypassing the built-in one. In addition to that, it is also possible to hand trigger the clock via a manual sample & hold button, which can be also modulated by gate signals.

Two Analog True-Random Modules in One

SAPÈL has two analog sample-and-hold circuits that generate eight random voltages simultaneously from analog thermal noise.

Each circuit has its own internal clock, which you can override with external trigs.

Versatile Clock and Triggering Circuit (Yes, With Buttons)

You can trig the four random generators in four ways:

  • With the internal clock;
  • With external trigs (overriding the internal clock);
  • With external signals (without overriding the internal clock);
  • With the built-in button.

You can also modulate the internal clock’s rate externally.

Random Clocks

Each random generator has a clock output and a Random clock output.

In Less Than mode, the Random clock outputs just some clocks here and there.

In More Than mode, it outputs more random clocks than the main one.

In both cases, the Global Rate of Change defines the random clock density.

Quantized Random Voltages (Revisited)

The 2ⁿ circuit generates random voltages precisely tuned to 12-EDO semitones.

The n+1 circuit outputs random voltages quantized to octaves.

Both circuits’ knobs define the n value, from 1 to 6: in this way, the 2ⁿ section can output 2, 4, 8, 16, 32, or 64 semitones, while the n+1 circuit can output 2, 3, 4, 5, 6, or 7 octaves.

We, of course, drew from the classic Buchla 266 but redesigned the circuit from scratch to provide a more even and “musical” value distribution.

Fluctuating Random Voltages (and Global Rate of Change)

This circuit generates a smooth, fluctuating random voltage.

It is the only random output that is not linked to the clock. It is a separate S&H circuit that integrates its values.

Its knob defines the fluctuation rate, from subtle, LFO-like frequencies to a sort of audio noise.

The Fluctuating Random knob also defines the random clock probability (Global Rate of Change).

True Unquantized S&H

Each generator has a classic, unquantized S&H circuit. Its wide range and its all-analog generation guarantee true noise: you won’t get two similar voltages in a row for a while!

The Colors of Noise

SAPÈL also has four analog noise outputs that provide Blue, White, Pink, and Red noise.

Hissing cymbals, roaring thunders, and windy seashores are at your fingertips.

Tame Your Randomness: Probability Distribution

This circuit allows you to control the average random voltage magnitude. From left to right, it will make the S&H circuits generate more low, mid, or high values, respectively.

On each section, you can route the Probability Distribution to each of the four random noise generators independently.


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.

We don’t sell directly. Please check our Reseller List to choose your favorite shop!

In Europe, we sell exclusively through our distributor: we do not have access to the individual shops’ orders or stocks.

In the rest of the world, we sell directly to the shops, but even in that case, there’s no way for us to know whether the modules that we’re restocking are sold, available, or reserved for another customer.

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.

If you experience abnormal behaviors with SAPÈL, check your case’s power supply and your system’s overall power consumption. For example, we experienced that SAPÈL sometimes has trouble working in a system close to its maximum Ampère output.
To solve this issue, try staying below 80% of the full amperage or switch to a more powerful PSU.