Format: Eurorack
Width: 18HP
Depth: 38mm
Current: 250mA @ + 12V, 170mA @ -12V
Manual PDF (English)
Frap Tools Sapel is a versatile random CV generator for Eurorack modular systems. The wide variety of random values generated by Sapel are sampled from analog thermal noise, adding true randomness to your patches. In addition to random voltage/clock generation sections, it also features four sections for generating audio noise .
The main section of the Chapel, which generates random voltages and clocks, consists of two independent channels, yellow and green.
Each channel has four sample and hold (S & H) circuits, three provide a stepwise random voltage, two are in notes, and one is not.The remaining one S & H circuit has an integrator, so the output is a voltage with continuous fluctuation.The three tiered voltage generators above are synchronized so that they can output three different values at the same time.
The yellow and green generators have two independent internal clocks that can be leveraged or temporarily overridden with an external gate or manual button.A copy of the trigger used for stepwise random value sampling, and a random trigger output are also available.The continuously changing voltage generator, on the other hand, is independent and has a control knob to define its own speed.Each aggregate is sampled from analog noise, providing true unpredictable randomness. The second section of the Sapel has four analog noise outputs, which are also used for sampling random values.
This section has a unique sound quality for each color and has four analog noise outputs available for sound design.The sockets shown in each color, which are lined up at the top and bottom of the right end of the module, are arranged from top to bottom as shown below.
The two generators, yellow and green, operate independently. Each simultaneously samples three random values: one unquantized ( S+H Out ), one quantized in semitone increments ( 2^n Out ), and one quantized in octave increments ( n+1 Out ).
There are four ways to trigger the S & H circuit of each generator, combining the clocks (internal or external) of both generators with a Single / Both switch in addition to the internal clock, external clock, S & H button operation, and external S & H gate. There is also an "extra mode".
Internal Clock & Clock Modulation
The built-in clock frequency is controlled by the Clock Rate knob in the center of the module.The clock frequency can also be modulated via the Gate / CV Modulation input, which allows the accompanying switch to select two different functions.When the switch is set to the right position, the incoming CV modulates the clock frequency, and when set to the left position, any input voltage above 2V is used to activate the S & H aggregate.
External Clock
You can activate the S & H circuit by patching an external trigger to the External Clock input.If the cable is patched to this input, the internal clock will be disabled and the S & H circuit will stop triggering.This input only accepts trigger and gate signals.This is because it requires an incoming signal with a steep rising edge, such as a square wave, a pulse wave, or a sawtooth wave with a negative ramp to sample a random value.Other types of impulses such as sine and triangle waves are ignored.
Clock mix
Both the yellow and green sections of the Sapel generate their own clocks.These can be blended in a more creative way by inputting the clock of the other generator to the clock of the generator in use by setting the Single / Both switch. To enable Clock Mix, set the switch to the position labeled with the colored square mark on the other generator.This feature, which affects only the sampling section, is valid for both internal and external clocks, and all clock outputs maintain normal operation.
Manual Sampling
The manual S&H button allows you to temporarily bypass either the internal or external clock. Pressing the button rewrites consecutive impulses to a gate-high signal, samples the value, and holds it until the button is released. The associated LED lights up while the button is pressed. The Main Clock output continues to output the trigger. ( See reference technique video: Hold)
External Gate Sampling
When the Gate / CV Modulation switch is set to the left position, the internal clock can be overwritten by patching a CV signal of 3V or higher to the Gate / CV input.This setting allows you to drive the S & H aggregate using signals other than gate / trigger.Sine waves, triangle waves, or internal Fluctuating Random can be used, but gates and square waves generally give the best results.
Clock Outputs (Main & Random)
Each time the S&H assembly samples a value, a 2-millisecond trigger is output from the Main Clock output. If a stable pulse, such as an internal or external clock, is used, this output provides a complete copy of the clock. The Random Clock output, located to the left of the Main Clock output, can perform addition/subtraction of the triggers in use. When the switch associated with this output is in the up position, it's in addition mode, adding a random clock to all generated clock impulses and outputting that. When the switch is in the down position, it's in subtraction mode, randomly subtracting triggers from those generated to trigger the S&H assembly and outputting that. In other words, it outputs only a portion of the triggers output from the Main Clock output. In either mode, the density of random clocks depends on the Global Rate of Change. See reference technique videos 1 , 2 , 3 , 4 , 5 , 6.
Each of Sapel's yellow or green generators features three types of stepped random outputs (one non-quantized and two quantized) and one type of continuously changing random output ( one fluidizing) . The characteristics of each output are as follows:
Non-Quantized Random Voltages
The basic stepped random voltage generator is a sample-and-hold circuit, outputting voltage values from the S&H output. This is an independent random generator, and the possible voltage values are stepless within the range of 0 to 7.5V . When this voltage is used for oscillator pitch control, etc., it will not fit within the conventional Western musical scale, so it is often used for more experimental music production or to modulate parameters other than melody, such as timbre, filter frequency, and amplitude.
Quantized Random Voltages
The two graduated random voltage generators output a voltage quantized to the 2 / Oct standard.The design of these two generators follows the Buchla 1 (Source of Uncertainty), but the approach is very different, aiming for a more random voltage distribution and extremely precise quantizing that can accurately generate semitones and octaves. Designed from scratch.
The main difference from the aforementioned S&H circuit is that, like the original 266 module, the Quantized Random generator has an n parameter that takes a value of 1, 2, ..., 6. The role of the n parameter differs for each output. The 2^n (2 to the power of n) output is quantized in 1/1,2V steps, which corresponds to a semitone on a 1V/Oct scale . In this case, the n Value knob sets the exponent of 2, thereby determining the number of values the circuit generates.
The larger the number, the larger the range of voltage (sound) generated, and the range from 1 (0V) to 64 (5.25V) is generated.This makes it possible to improve the controllability of the final output, that is, the power of expression.For example, a low n value will always produce a low note with narrow intervals, and a high value will produce a lively high note in semitones.The graph below shows the distribution of exponential notes at all n settings.
The n+1 output is quantized in 1V steps, resulting in an octave on a 1V/Oct scale . In this case, the n+1 Value knob sets the number added to 1, which determines the number of different octaves the circuit can generate. Again, since n is any number from 1 to 6, the circuit can generate a range of 6 octaves.
Even in this case, as the number increases, the range of the generated voltage (or octave) expands, and it becomes from 1 (0V) to 7 (6V).The graph below shows a linear increase in octave when the n setting is changed.
Both 2n and n+1 support control via external CV, allowing for automated changes to the range of output values. See reference technique videos 1 and 2.
Fluctuating Random Output
The main purpose of this section is to output a random voltage that continuously fluctuates within the range of 0 to 7.5V, and its rate of change (or frequency) is controlled by the FRV Rate & Global Rate of Change knob.
This random generator is unique in that it is not affected by the main clock or gate, but it does affect the clock generation itself. The secondary purpose of this section is to control the rate of change of the random clock; the FRV Rate knob controls both the FRV frequency and the random clock density. Similar to the Quantized Voltage generator, this parameter can be modulated with any CV via the accompanying CV input, and external modulation also affects both the FRV frequency and random clock density. ( See reference technique video)
Probability Distribution (Stored Random Voltages)
The four random generators mentioned above can also control the probability distribution of the generated voltages . This parameter is called the Probability Distribution and is set commonly for each color via the Probability Distribution knob, and can be enabled independently for each output using the four Probability Distribution switches. The PD knob sets the range of voltages that are generated more frequently. In the middle position, medium voltages are output most frequently. Turning the knob to the left increases the probability of lower voltages being generated, and turning it to the right increases the probability of higher voltages being generated.
SAPEL Tamed Random Source - Overview from Frap Tools on Vimeo.
