Skip to main content

250e Arbitrary Function Generator

The 250e is a 16 stage function generator. Each stage stores two control voltages, which are set with an array of 16 potentiometers. Time values are adjusted with a parallel array of smaller potentiometers, and can serve as a third control voltage. Time can also be synchronized to MIDI clock sent via the 225e. Both control voltages and times can be interpolated, quantized, or replaced with externally applied voltages for selected stages. Additionally, there are two programmable pulse outputs, as well as a facility for voltage control of stage position. Loop counters associated with each stage can be nested to any level.

EDITING: Data base editing Voltages and times can always be edited – just turn the knob associated with each stage to the desired value; to change ranges for either, you must enter the Edit mode, (depress the Edit switch). Turn the center knob to the desired stage, chose the desired time range (one of three) and the voltage range (one of six). Also select the voltage you’d like to operate on (one or two). Each of the two voltages, as well as the time can be quantized – voltage in .1 volt increments, time in binary rhythmic increments of .01, .02, .04, .08, .16, .32, .64, 1.28, 2.56, 5.12. Time values may be modified through application of an external control voltage scaled from 1/2 to 2. Additional fixed scaling over a range of .25 through 4.0 may be achieved with a dedicated pot. A red quantize LED alerts you that you’re very close to the edge of a quantize value. So keep it in the green. The clock of the 250e can be synchronized to MIDI clock via a 225e. This can be selected on a stage by stage basis by setting the time range to the fourth (blank) value. All modes which require an internal clock to count down (ADV, SUST, ENA) will now wait for an appropriate number of MIDI clock ticks before proceeding. This clock division is set via the small time knob to one of seven values: 
 1) thirty-second note 5) eighth note
 2) sixteenth note triplet 6) quarter note triplet
 3) sixteenth note 7) quarter note
 4) eighth note triplet

If stage 1 is set to use MIDI clock then MIDI start and stop will be obeyed as well. Upon receiving a MIDI start the sequencer will immediately reset to stage 1 for playback. When using MIDI clock the time mult knob and external voltage won’t affect the clock division but will affect the interpolation time.
 EXTERNAL INPUTS: Voltages and times may be derived from external control voltage inputs on a stage by stage basis. Controls for this trick reside in the lower left section. While in the edit mode, select the desired stage number and switch on the time and/or voltage LED’s with the associated switches. Be sure to select the desired output voltage (1 or 2). If these LEDs are on, then the stage pot, instead of setting a voltage or time, chooses between four inputs -- A, B, C or D -- for that stage. (Each stage follows the same selection scheme as drawn on stage 1). Use “fix” to grab an external voltage. The incoming voltage at the time “fix” is pressed becomes the fixed voltage, storing current values as if they were knob settings. This can be a great short cut for storing a voltage in each stage without having to turn all the knobs. Fix is a global control, and when on, (“fix”) disables external inputs. It can be turn on and off outside of editing.

PULSE OUTPUTS: Pulse outputs are edited on the right side. All stages produce pulses at the “all” output, while pulses 1 and 2 are selected by toggling the associated switches while in the edit mode. Illuminated LED’s indicate active pulses. Editing shortcut: As an editing convenience, we offer a method of quickly programming identical switch settings in any number of adjacent stages: While in the edit mode, select the value desired for a particular switch, and while still depressing the switch, rotate the edit select through all the stages you’d like programmed to this switch value.


Stage Selection: MODES The 250e offers several schemes for stage selection. Pulse Mode – This is the default mode for a stage and is indicated when none of the mode LED’s are on. A pulse applied to the Start / Adv input or a press of the switch will advance to the next stage. Advance Mode – This mode is indicated when the “adv” LED is on. The stage will only advance when the time value runs out. Sustain Mode – This mode is indicated when the “sust” LED is on. The stage will advance when the time value runs out. However, if a gate is applied to the Start / Adv input the stage will pause (sustain). When the gate goes low the stage will continue to run based on its time value. Enable Mode – This mode is indicated when the “enbl” LED is on. This is the opposite of the Sustain mode; the stage will pause until a gate is applied to the Start / Adv input. At this point the stage will run based on its time value until the gate goes low again. Stop Mode – This mode is indicated when the “stop” LED is on. This will cause the sequence to stop on the selected stage. A pulse to the Start / Adv input or a press of the button will continue the sequence. Pressing the “stop” button or applying a pulse to the “stop” input will also cause a stage to enter this mode.

**Stage Selection: Jump and loop​

In the upper center, we encounter a jump and loop facility, in which the subsequent stage is determined by some programmable logic. While in the edit mode, use the center knob to select a loop’s last stage; then hit “set” and use the center knob to select the loop’s first stage. The “jump to” LED’s in the bottom of the display will be on here. Hit “set” again to activate the loop counter and dial in the desired loop count. The loop count LED’s in the bottom of the display will be on here. Hit “set” to return to the normal edit mode.**

Stage Selection: STAGE ADDRESSING A third scheme for stage selection is presented in the lower right section. When in continuous mode, the stage number is determined by the applied control voltage. An offset control establishes the stage number for an input voltage of zero; sensitivity to an applied control voltage is .625 volts per stage. (A full scale excursion of 16 stages corresponds to 10 volts applied control voltage.) When “strobed” is active, the control is sampled, resulting in changes only when a pulse is applied.
This can result in fascinating non-linear variations, especially when the input pulse and the applied CV are independent from each other.

Remote Enable When active, this LED puts the 250e into contact with the preset manager, allowing access to stored preset values.