Primary Functions: Stepped Random Voltage Function Smooth Random Voltage Function

Secondary Functions: Sample and Hold • VC Slew Limiter • A/D Generator • Quantized Random Pulse Generator • Gate to Trigger Converter (Gate in out to 3ms Trigger out) • Digital Noise Source

The Model 24 Heisenberg Generator is the first computer-based module in the Plan B line. Taking it's name from Werner Heisenberg (the father of the Uncertainty Principle), the Model 24's primary function is a dual wide-band random voltage generator producing simultaneous and fully independent stepped and smooth arbitrary voltages. Along with these random events, it can also be used as a Sample and Hold, a VC Lag Processor, a VC Trigger Generator, a Gate to Trigger Converter or a Digital Noise Source. The Model 24 also provides VC inputs for all of its tactile controls. While totally self contained - producing its own pacing triggers and random states - its also open ended, and will accept external triggers and voltages independently. A true analog/digital hybrid (Click here for a block diagram), the M24's on-board 10mHz Atmel 2051 microcontroller serves three primary functions: 1) Digital Noise. Two independent algorithms replicate the functionality of the long-extinct National MM5837 Digital Noise chip..with 16 bit resolutionThere are no D to A converters in the Model 24. There will be no zippering (stepping). An analog source is derived by filtering a flurry of 2 x 64,000 possible random gate signals generated by the 2051. All secondary processing (Mean, Deviation, Chaos, Meter) is executed in an analog domain. 2) Clocking. The second function assigned to the microprocessor involves two pseudo-random trigger streams, both quantized internally to 8 (smooth) and 5 (stepped) degrees of musical time:

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Figure 1 - Internal trigger streams of the Model 24

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Figure 3 - MEAN and DEVIATION controls

The Mean pot sets the relative midpoint, the vertical displacement of the output voltage's center point (see figure 4).

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Figure 4 -Effects of MEAN adjustment on a single waveform

The Deviation pot controls the variance (both positive and negative) from the mean, the spread from the midpoint (figure 5) .

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Figure 5 - Effects of DEVIATION control settings on a single waveform. MEAN remains constant

The voltage patterns shown in figures 4 and 5 are identical, yet illustrate the effects of various settings of the MEAN and DEVIATION controls.

I/Os:

Outputs: All of the Model 24's critical signals are brought to the user interface. Along with the stepped voltage output, it's internal trigger is also available (TRIG OUT) so that external devices such as envelopes and other triggerable control generators can be easily synced with the M24's pseudo-random musical intervals. The smooth generator also makes it's internal noise generator available (SOURCE OUT).

Inputs: The Stepped generator has a dedicated input for an external drive (EXT TRIG). Another interesting feature can be easily patched by setting the DEVIATION pot fully CCW while controlling the MEAN function by an external signal. The otherwise steady state behaves as a Sample + Hold (stepped gen.) or a Slew Limiter (smooth gen.) Set up in this fashion, output voltages of the stepped and smooth generators track the VC MEAN signal, with the pot acting as a manual offset to the incoming voltage. The Stepped Generator holds these voltages until the next trigger is recevied, the Smooth Generator applies a portemento, the slew time (ranging from .5 seconds to OVER FOUR MINUTES!!!) determined by the CHAOS pot setting.

Theoretical Notes:

The design of a stepped random voltage function is a relatively easy analog computation. A smooth random function however, as defined in the M24 as a sloping, continious random event is much more involved. Three key elements (the range of the internal VC LFO driving the quantized random pulse generator, the algorithm incorporated to generate those quantized random triggers, and the slew rate of the VC lag processor) continually interact to create the final outcome and must track one another in tight unison to maintain a unified personality over the entire range of a single pot (Chaos) and to keep from stalling. In the case of the Heisenberg, many considerations had to be met to achieve this goal, as the elements involved cross betwen the analog and digital domains twice before their final analog processing (sample and hold and slew limiiting). We feel the Model 24 meets and exceeds those expectations.

Sample Patches:

While operation of it's two primary functions (Stepped Random and Smooth Random) is intuitive and fully indepentent of one another (two independent random voltages simultaneously, each having it's own control of speed, center point and vertical displacement), some of the M24's secondary uses are diagramed below:

Sample and Hold

Digital Noise

VC Slew Generator

Gate to Trigger Converter

Quantized Smooth Voltage (Arbitrary or stepped processing of Smoothed Out - not quantized in an equal tempered sense of half or whole steps)

Random Quantized Trigger Gen (random musical timings)


To increase the range/chaos fluctuation of the SMOOTH output, try the folllowing:

A) Patch the STEPPED RANDOM OUTPUT into the SMOOTH RANDOM VC MEAN INPUT

Settings:

1) SMOOTH OUTPUT MEAN and DEVATION pots to full CCW.

2) SMOOTH OUTPUT CHAOS to taste

3) STEPPED RANDOM's MEAN pot fully CCW

4) STEPPED RANDOM DEVIATION to 2 o'clock

5) STEPPED RANDOM PERIOD - start at 8 o'clock, adjust to taste.

For a diagrom of this setup, click here

This pach will, among other things, improve the performace when using the Smooth Random to control placement of a Stereo Panner.

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Audio Samples:

Outside of reverb and delay (via Digital Performer), the following samples were done entirely in a Plan B domain:

Stepped Random 1 - An example of fairly generic use of the Model 24's Stepped output. Run on it's own random pulses, those being used to trigger a Model 10 that's gating the M15 through a Model 13 set to Lowpass mode. The METER (speed) of the M24 is at about 2 (out of 10) and it's MEAN is at about 7. The VC atenuator of the M15 is only half way up. There is slight panning induced by the M24's smooth output. While the output pacing is random, note that iis stays within meter (musical time).

Stepped Random 2 - Same patch as above, althought this time the meter is faster and the range of the VC on the Model 15, and the Mean of the Model 24 has been increased

Stepped Random 3 - Same patch as above, this time being paced externally by a Model 15

Stepped w/voltage controlled MEAN - Same patch as above, this time a Model 10 in Log contour is being used to slowly increase the MEAN range form Null to about 75%

Sample and Hold - A single Model 15 is being controlled by the stepped output of a Model 24 configured as a sample and hold. The source is a Model 10 used as a ramp LFO, it's duration being controlled by a second Model 24 that's being paced the the M10 End of Cycle pulse. There is slight panning by the Model 24's smoothed output.

Sample and Hold 2 -Dual Model 15s being controlled by the stepped output of two Model 24s configured as sample and holds, with changes coming from occational interjections of keyboard voltages into the VC Deviation inputs of both, taking it fom a repeated phrase and introducing random into that. Gating via a Model 13.

Filter Sweeps - Three Model 15s, two being amplitude gated by two Model 24 smooth random voltages using a Model 14 crossfader, being fed into two Model 12 Bandpass Filters in series, both of those being swept in frequency by a single (third) smooth Model 24 output

Smooth Output 1 - A really boilerplate example ofthe smooth output voltage left to it's own means witout any voltage control. The MEAN pot is at about 3 o'clock, the VC attenuator is only about 3/4 of the way up. Note the range. The CHAOS pot is at about 2 (out of 10). Not as slow as it goes, but a fairly lazy pace.

Smooth Output 2 - Same patch as above, but the Chaos starts off at about 11 O'clock and is tuurned up towards the end.

Smooth Output 3 - Smooth output controlling the frequency of a VCO with a external voltage control applied to the VC Chaos input. You can hear the effect of the low frequency triangle wave (Actually a self-cycling Model 10 in Log contour) effecting the output

Smooth Output 4 - Same patch as above with additional pot tweeks.

Stepped Smooth - In this example, the Smooth output of a single Model 24 is being processed by it's own Stepped Generator. Along with the Model 15 you're hearing, those voltages are being used to control the freq of another Model 15 which is pacing the S + H.

Slew Processor/AD Generator - Three examples, first two of the shortest slew time, last one at about 2 (out of 10), so slower, but not as slow as it gets. In bioth instances it's processing a gate.

Source Output - Although brought to the faceplate to be used as a source of secondary random voltage generated by external devices, this sample gives you an idea what the source output sounds like unprocessed. This is the signal which the Model 24 derives all of it's internal random voltages. Phil Hendricks will dig this.

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