I'm revisiting the Buchla 200e and slowly going through all the old manuals notes etc.
So this is a running thread which I'll update as I discover new things about the module.
To start, the 250e is what's known as a DARF ... dual arbitary function generator.
What's a Function Generator?
In the early days a FG (function generator) was a piece of test equipment used to generate different types of waveforms.
It had nothing to do with modular synthesizers in those days
Kenwood FG273 from the 1990s
Don chose to add the word "Arbitary" ... meaning based on random choice or personal whim.
I think Don's choice of words gives an insight into the character of the module.
The 250e is related to the earlier Buchla 248 MARF ...
see my notes on this.
The 250e DAFG a 16 stage FG (function generator).
It's divided into these sections:
1. stage array
2. Stage loop & editing
3. Mode
4. Time
5. Voltage
6. Pulse output
7. Stage addressing
8. External inputs
1 Stage Array
There are two circular rows . Each row has 16 pots.
Each pot pair represents a stage.
Each stage has 2 control voltages.
Time values are often adjusted with the parallel array of smaller potentiometers. These can serve as a third control voltage.
Both control voltages and times can be interpolated, quantized, or replaced with externally applied voltages for selected stages.
Just turn the knob associated with each stage to the desired value to adjust voltages & times.
To change ranges for either, you must enter the Edit mode, (depress the Edit button in the stage loop & editing section). 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).
2. Stage loop & editing
There are 2 LED displays, 3 buttons and one knob.
To adjust and set voltages & voltage ranges you must enter the Edit mode by depressing the Edit button.
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
Voltages are adjusted in .1 volt increments.
Time is adjusted in binary rhythmic increments of .01, .02, .04, .08, .16, .32, .64, 1.28, 2.56, 5.12.
There is a quick way to program identical settings ... eg to clear everything or to set each stage to the same voltage or time.
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.
Notice, there is also a Jump & Loop facility.
Here we can set subsequent stages.
While in the edit mode, use the center knob to select a loop’s last stage; then hit “set” and then
use the center knob to select the loop’s first stage. You will now see that the "Jump to" LED will be lit.
Hit “set” again to activate the loop.
Now using the centre knob dial in the desired loop count.
A value of A = Always.
You will now see that the "loop count" LED will be lit.
Hit “set” to return to the normal edit mode.
Loop counters associated with each stage can be nested to any level
Remote Enable
When active, this LED puts the 250e into contact with the preset manager, allowing access to stored preset values.
3. Mode
This is where you set up your mode for stage selection.
There are 5 modes: Pulse, Advance, Sustain, Enable, Stop.
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. You can consider this to be your "conventional sequencer mode" if you set your time base knobs (the small knobs in your array section) to zero. adjusting the small knobs set the time spent on each stage.
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 is the opposite of Sustain Mode. This mode is indicated when the “enbl” LED is on. 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
4. Time
To change the time range of a stage.
1. press the edit button
2. turn the centre knob to select the stage you wish to edit.
3. Press the time range button to the desired value.
Note that when cycling through your time ranges there is a blank option when no LEDs are lit. This is
the option you would use to sync to a midi clock.
The
blue time CV out banana gives us access to the voltages from the small time knobs of the Stage Array Section.
As discussed above, the clock of the 250e can be synchronized to MIDI clock via a 225e (using the internal bus).
This can be selected by setting the time range
to the fourth (blank) value.
The MIDI sync can be set on a stage by stage basis.
To set an individual stage to slave to the MIDI clock remember to assign the time range of the stage to a blank value.
When using MIDI clock, the time mult knob (in the Time section) or external voltage wont affect clock divisions but will effect the interpolation time.
The clock division can now be set via the small time knob (in the 1.stage array section ) 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
5. Voltage
There are 2 CV voltage outputs.
The grey button to the right of the two voltage LEDs selects which CV voltage the large outer knobs
(in the CV array section) set.
You don't have to press the edit button to jump between voltages 1 and 2.
You need to hit the edit button to change voltage ranges.
6. Pulse output
There are two programmable pulse outputs for each stage.
All stages produce pulses at the “all” output, while pulses 1 and 2 are selected by pressing the associated grey buttons for each stage while in the edit mode.
Use the central knob to select the stage as usual.
When you press RUN, the illuminated LED’s indicate the active pulses.
7. Stage addressing
Here we have another way to select the stage (see 3.Mode)
These third schemes for stage selection are presented in the lower right section.
We have 3 modes: Blank, Strobed & Continuous.
Press the grey button to choose between the three.
When in
Blank Mode: No lit LEDS.
When in
Continuous Mode, the stage number is determined by an applied control voltage in the black
banana jack marked CV in. A full scale excursion of 16 stages corresponds to 10 volts applied control voltage.
When in
Strobed Mode, the control is sampled, resulting in changes only when a pulse is applied at the orange banana.
The offset control knob establishes the stage number for an input control voltage of zero.
Sensitivity to applied control voltages is 0.625v per stage with zero volts being stage 1 and 10V being stage 16.
8. External inputs
The controls for this rest in the lower left section.
Voltages and times may be derived from external control voltage inputs on a stage by stage basis.
There are 4 inputs: A, B, C, D.
Make sure you are in edit mode. Now select the desired stage number and switch on
the time and/or voltage LED’s with the associated switches.
You can use a external CV for each of the large CV knobs or the smaller time knobs (in the CV array section). Also the external voltage option can be assigned to CV 1 &/or CV2 independently with different values for each. Be sure to
select the desired voltage (1 or 2).
The stage pots now change function, choosing which of four inputs to select.
Notice the letters (ABCD) around both the large CV knob and small time knob.
Use these when assigning which external input will effect the stage chosen.
Only the 12"oclock knobs have these letters marked.... doesn't mean that you can't do the same for the other stages. For the rest of the stages just pretend the letters are there.
A global control (“fix”) disables external inputs, storing current values as if they were knob settings.
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