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250e-md

Buchla 250e

The Buchla 250e

Arbitrary Function Generator​

The 250e is a 16-stage voltage-sequencing module.

A "function generator" is a piece of electronic equipment that generates waveforms. The 250e is capable of this possibility as well, due to the fact that it can run at high speeds and use interpolation to create gradual changes between voltage points.

Voltage​

The outer ring of knobs sets the voltages for the 16 stages of the 250e. These voltages can be set, stored in presets, and changed at any time.

With a press of the "quant" button, these voltages can be quantized to values associated with notes. Keep an eye on the quantize LED while setting values. It will glow green when you're within the "comfortable" range of a value, but will turn red if you're close to the edge of the next value.

With a press of the "interp" button, the changes between stage voltages can be made to be gradual, which, when voltages are being used as notes, create a sort of "portamento" effect between stage voltages.

It is possible to adjust the voltage range of each stage, allowing you to refine how that stage's voltage output behaves. The voltage range default is "all (0-10v)," but can be adjusted to different ranges by pressing the "voltage range" button.

The 250e allows for two sets of 16 voltages. The first is the default setting, which is indicated by the "1" LED being lit next to the word "VOLTAGE." By pressing the "2" button, you have a second set of 16 voltages and associated settings available. Voltage set 1 is output from the first "cv output" blue banana jack, and the second is output from the second "cv output" blue banana jack.

Pulses​

For a stage to trigger, for example, an envelope on the 281e, pulses must be assigned to stages. This is to say that you can start the 250e, but if you have it set up to trigger a normal oscillator/envelope/LPG architecture, you're going to need to assign pulses in the "PULSE OUTPUTS" section.

To set pulses, press the "edit" button, turn the knob in the center of the circles of knobs to the stage you desire a pulse (a blue LED will light next to the stage numbers), and press one or both of the pulse buttons in the PULSE OUTPUTS section. The buttons you press will activate an LED showing you which pulses exist on the stage you've selected. The red banana jack associated with Pulse 1 or Pulse 2 will output those pulses, and the "all" jack will output a combination of the pulses present on each stage.

Time​

The inner ring of smaller knobs set the time interval for each stage.

The value of the stages of the time ring is affected by the time settings. The large knob adjusts fixed scaling. There is a black banana input that allows voltage-controlled variations in time. The range of time addressed by the knobs in the stages can be set (in edit mode) with the "time range" button.

Pressing the "quant" button will quantize the time values in each stage to note values. Like the quantizing of the voltage sections, a red LED will indicate you're too close to a value change, and a green LED will indicate you're comfortably at a value.

Pressing the "interp" button, like with the voltages, will create a gradual change in the time between time values.

The blue "cv out" banana jack outputs the voltages associated with the time setting of each stage, resulting in a modulation output. If "interp" is activated, the output voltages will have gradual movement between the voltages, resulting in a waveform.

MIDI clock sync​

The clock of the 250e can be synchronized to the MIDI clock output of the 225e. This sync can be selected in individual stages, and is achieved by pressing the "time range" button until no LED is lit, and doing so on each stage you want MIDI-controlled. Setting the "time range" to the no-LED setting breaks the time knob into time divisions as follows:

  1. Thirty-second note

  2. Sixteenth-note triplet

  3. Sixteenth note

  4. Eighth note triplet

  5. Eighth note

  6. Quarter note triplet

  7. Quarter note

    Getting the 250e clock to obey MIDI start and stop If stage 1 is set to the no-LED fourth setting of "time range," the 250e will respond to MIDI start and stop messages. When the 250e receives a MIDI start message, it will reset to stage one to play. When using MIDI clock, the Time Mult knob and the external voltage knob will not affect the clock, but these knob setting will affect interpolation time.

External voltage control​

Each stage can be set to receive voltage control in regard to voltage and time from external sources. Plugging external voltage sources to the A-D banana jacks in the lower left and then pressing the "time" and/or "vltg" buttons allows you to control a stage from an external voltage source. Pressing the buttons disables the voltage and/or time knobs as voltage settings and converts them to jack input selectors.

For example, if you wanted an external voltage plugged into the "A" banana jack to control the voltage of step 1 of the second set of voltages, you would:

  1. Press "edit."

  2. Press the "2" button next to the word "VOLTAGES."

  3. Select stage 1 with the center knob

  4. Press "vltg" to light the LED

  5. Turn the stage 1 voltage knob to A, as indicated on the diagram (this diagram is only on stage 1, but applies to setting inputs on all stages)

    If you wanted the time of stage 1 to be controlled by the external control voltage input to the "B" banana jack, you would:

  6. Press "edit."

  7. Select stage 1 with the center knob

  8. Press "time" to light the LED

  9. Turn the stage 1 time knob to "B" as indicated by the diagram (this diagram is only on stage 1, but applies to setting inputs on all stages)

    The "fix" button allows you to set a stage to the voltage that is input to the jack that the knob is set to when you press the "fix" button (after having selected the type of external control via the "vltg" or "time" buttons, and selected the desired jack with the voltage or time knobs associated with the stage you're on). This is a great shortcut to allow you to quickly set the voltages of knobs without having to do so manually with the voltage knobs.

    When the "fix" button is pressed and the LED is lit, it disables the external inputs for that stage.

Pulse Mode​

On the left side of the module, there is a section that addresses how the 250e will be started and stopped. There is a green "start" button, and an orange "stop" button as well as pulse inputs for applying a pulse to start or stop. When the sequence has been started, the green LED next to the "start" orange banana input will be lit. The default mode is one where the buttons and inputs start and stop the sequence.

There are four other pulse modes:

  1. Advance Mode (adv): When you have selected this mode by pressing the pulse mode button, the stage will only advance to the next stage when the time setting for that stage runs out, irrespective of pulse inputs.

  2. Sustain Mode (sust): When you have selected this mode by pressing the pulse mode button, the stage will advance when the time setting of the stage runs out. When a gate is applied to the orange banana input, the sequence will pause until the voltage of the gate drops. Once the gate voltage drops, the stage will continue until its time setting runs out.

  3. Enable Mode (enble): When you have selected this mode by pressing the pulse mode button, the stage will pause until a gate is applied to the "start" input. The stage will then run its time value until the gate voltage drops.

  4. Stop Mode (stop): When you have selected this mode by pressing the pulse mode button, the selected stage will stop when it is reached. A pulse to the input will restart the sequence.

Jump and Loop​

With the 250e, it is possible to create loops within the sequence, and even loops within the loops. The sequence will jump to a selected stage in the midst of play for an adjustable amount of times and then continue through the sequence.

Setting this function might feel a bit backward, but it occurs like this:

  1. Press the "edit" button

  2. Use the center knob to select the stage at which you would like your loop to end

  3. Press the "set" button in the loop section in the center of the module

  4. LED dots will appear in the "jump to" window

  5. Use the center knob to select the stage at which you would like your loop to start

  6. Press the "set" button

  7. LED dots will appear in the bottom of the "& loop" window

  8. Use the center knob to set how many times you would like this loop to occur

  9. Press "set" to exit the setup

Stage Addressing​

On the lower right, there is a facility for using voltage control and pulses to address the movement of the sequence between stages. It allows the input of voltage and pulse to control stage movement.

Strobed: This function operates a bit like a sample and hold… the pulses activate selection of the current state of the voltage that is input and use that voltage to select a stage. The 16 stages are divided by 10 volts; the higher the voltage, the higher the stage.

Continuous: The stage number is selected by the voltage, or variation of voltage, that is input alone.

Remote Enable​

To connect or disconnect this module from the central library function, press the "Remote Enable" button. Connection is indicated by a lit LED.