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Cell Manual
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CELL Manual

Rat King Modular

General Info

The CELL is a standalone semi-modular synthesizer voice that combines some east coast and some west coast elements. It contains a single voltage controlled AS3340 oscillator (VCO), a low pass voltage controlled AS3372 filter (VCF) and amplifier (VCA) combination, and an AS3310 voltage controlled envelope (EG), a voltage controlled slope (VCE). Lastly there is the Random Sequencer (RND) that ties the various modules together. There is a "normallization" path that internally patches the individual modules together so that a user can have a basic patch available without the use of patch cables. The specific circuits were chosen for their stability, versatility, availability, and ease of construction.

Now, for a box this size there has to be some tradeoffs between flexibility and economy, namely in the audio path which is normallized (vco>mixer>vcf>vca>out). This normallized path is fixed and cannot be altered. The modulation path contains some normallization that offers the user immediate access to basic patches that are most often used. The Random Sequencer CV output is normallized to the VCOs attenuated CV input (CONTROL). The clock output of the Random Sequencer is normallized to the VCE and the EG. The VCE's TRIG input is normallized to the RND clock out while its output is normallized to the CV input of the VCA. The EG's output is normallized to the VCF's CV input.

There is a console and a Eurorack version of the CELL. The controls and patching are identical between the two versions.

To simplify patching, output jacks have a gold circle around them. Jacks without a gold circle are input jacks.

If you bought a DIY version, click here for the bill of materials and assembly guide.

Power consumption:

VCO

Although the oscillator presented in the circuit is rather standard these days, the 3340 style VCO is highly stable and offers a wide and accurate range. Included in this module are Coarse and Fine tune controls, 1V/OCT CV input for connection to a modulation source, a synchronisation input, a linear Frequency Modulation (FM) input, and an attenuated exponential CV input which is normalled to the Random Sequencer CV output.

Jacks

1 V/O - One volt per octave voltage input

Sync - Synchronization input

FM - Frequency modulation input

CV - Exponential control voltage input

SHAPE CV - Shape control CV input

VCA CV - VCA CV input

Pots

TUNE - Fine pitch control

FREQUENCY - Coarse pitch control

CONTROL - Exponential CV input attenuator

SHAPE - counterclockwise: square, clockwise: saw, in between: mix

Trimmers

Calibration instructions can be found at the end of the manual.

SCALE - 1V/O Trimmer

HF - High Frequency Trimmer

VCF

One of the more unique features is the incorporation of the AS3372 VCA/VCA integrated circuit. This is the reproduction of the CEM3372 used in the Oberheim Xpander and others. Personally, this filter sounds very Roland-ish to my ears, and is perfect for acid-style basslines. There is an attenuated CV input for the VCF that is normalled to the output of the AS3310 ADSR Envelope Generator. The "Q" control can reach self-oscillation at full resonance.

The 3372 includes three Voltage Controlled Amplifiers. One of the amplifiers is being used in the standard output configuration and includes a CV input that is normalled to the CV output of the VCE. Also contained within the 3372 are two more VCAs that make up a crossfader. Therefore I have incorporated this circuit as a kind of voltage controlled mixer for the VCF input that sweeps between the square and saw wave shapes. As the signal input to the filter is swept from one shape to the other, the signal develops a more nasal-sounding character. In this instance it is best not to think of the basic shapes as saw and square, but as "brassy" and "reedy" where sound becomes more or less "nasally" through the sweep.

Jacks

CV - CV over cutoff input

Pots

Q - Resonance control

CUTOFF - Low pass filter cutoff frequency control

CONTROL - CV over cutoff input CV attenuator

Trimmer

Calibration instructions can be found at the end of the manual.

FSCL (Filter Scale) - scales the VCF cutoff to 1v/oct

VCE

The next module is an adaptation of what is arguably one of the top 5 most well-known modules: the voltage controlled slope (in this case Voltage Controlled Envelope). In our version, a function that is electronically present within the circuit is brought to the surface. There is the input that can also accept a Gate or CV input, then a dedicated trigger input that allows for short transients to be produced. Control over the onset and duration by CV, envelope out and an end of cycle gate (EOC) which can be self patched to produce short or long cycling waveshapes. The possibilities for this module are vast.

Jacks

EG - Envelope output

EOC - End of cycle gate output

OCV - CV over onset input

DCV - CV over duration input

GATE - Gate input

TRIG - Trigger input

Pots

ONSET - Length of onset control

DURATION - Length of duration control

EG

This module is a standard ADSR type Envelope Generator (EG). Not too much to say about this one. This module provides a convenient extra modulation source. Based on the AS3310 IC.

Jacks

EG - Envelope output

GATE - Gate input

Pots

ATTACK - Length of attack control

DECAY - Length of decay control

SUSTAIN - Length of sustain control

RELEASE - Length of release control

RND

Lastly is the Random Sequencer which produces pseudo generative and repeatable sequences. Select between random, 16-step repeated or 8-step repeated sequences that are quantized to musical intervals at a range of approximately 0-5v. The clock input (CLK) allows for an external clock source (when the rate knob is set at noon). Many early electro basslines are in this thing but be sure to record them as the circuit cannot recall any previous sequences, and powering off will reset the sequence.

Jacks

CLK OUT - Clock output

CLK IN - Clock input

RND - Random voltage output

Pot

RATE - Rate/speed of clock/sequence control

Switch

MODE - R: continuous random voltages; 16: repeating 16 random voltages; 8: repeating 8 random voltages

Calibration

SCALE

  1. On the front of the panel (using the FREQUENCY and TUNE controls), tune to a fundamental frequency that can be easily verified several octaves up (e.g. 20Hz, 50Hz or 100Hz).
  2. Apply 1V to the 1V/O input.
  3. Adjust the SCALE trimmer to 2x the initial frequency.
  4. Apply 0V to the 1V/O input.
  5. Readjust the FREQUENCY/TUNE pots the front panel to match initial frequency.
  6. Repeat steps 1-5 until 1V is 2x the original frequency.
  7. Repeat steps 1-6 until the first 6-8 octaves are calibrated, or you’re satisfied with the range that is calibrated.

HF

This should only affect tracking at high frequencies, where there can be a slight drop in current within the exponential generator inside of the 3340 IC.

  1. Calibrate the 1V/O trimmer first.
  2. On the front of the panel (using coarse and fine controls), tune to a very high frequency (e.g. 2kHz, 4kHz, 8kHz).
  3. Apply 1V to the 1V/O input.
  4. Adjust trimmer to 2x the initial frequency.
  5. Apply 0V to the 1V/O input.
  6. Readjust the FREQUENCY/TUNE pots the front panel to match initial HIGH frequency.
  7. Repeat steps 3-6 until that octave is calibrated.
  8. Repeat steps 3-7 for each successive octave until satisfied.