259e-md
![Buchla Module](C:buchla_doc/static/img/200e/259e.jpg "Buchla 259e”)
The Buchla 259e
Twisted Waveform Generator
The 259e is an oscillator module that is comprised of two modules; a "principal" oscillator and a modulation oscillator. The design, based on the 200 series oscillator concept, is one where the principal oscillator is modulated by the modulation oscillator, giving a much wider and more interesting range of generated waves than could be achieved with a typical single electronic oscillator with traditional waveshapes.
The Principal Oscillator
The Principal Oscillator is a sine wave oscillator that generates a frequency range of 27Hz to 7040Hz. There are two jacks that provide external modulation of the oscillator frequency: one audio jack for audio frequency modulation with a dedicated knob, and one banana jack for control voltage frequency modulation with a dedicated attenuverter.
Above the main frequency knob is a small trim for fine oscillator tuning.
The Timbre section
Above the frequency section of the Principal Oscillator is the Timbre section, where the wavetable aspect of the Principal Oscillator can be controlled.
There are five combinations of two wavetables and three "memory bank" choices to choose from in the Timbre section.
When pressed, the grey "TIMBRE" button selects one of five wavetables or memory banks. When the button is held, it will switch between the "green" setting and the "red setting." Which setting you're currently on is indicated by one of the two LEDs directly above the TIMBRE button.
So, for example, when green LED is lit, you could select wavetable "3." Then you could press and hold the grey button to switch from green to red, where the red LED is lit. Then you could select wavetable "5." In that way, you have selected two wavetables that are available for the Principal Oscillator, and driven by the Principal Oscillator's sine wave.
Morph
The "morph" knob allows you to select either the green wavetable or the red wavetable you've selected, or select a position in between right and left to mix them both. With the knob arrow straight up, you have equal amounts of both. Your balance of red vs. green is indicated by LEDs beneath the knob.
There is a control voltage input banana associated with the Morph function, and an attenuverter that allows you to apply the voltage in both positive and negative ways, allowing you to control which wavetable occurs at what point in your set of two. Keep in mind that the greatest variance of control is possible when the Morph knob is turned completely to the left, despite this seeming to indicate only one color will be affected.
Warp
The "warp" knob allows you to vary the amplitude of the sine wave that is driving the wavetables, resulting in a timbral change.
There is a control voltage input banana associated with the Warp function, and an attenuverter that allows you to apply th voltage in both positive and negative ways, allowing you to control the intensity of the control of the effect. Keep in mind that the greatest control of the effect occurs when the "warp" knob is turned entirely to the left.
Memory Bank and Memory Skew
Selections "a," "b," and "c," which are marked "memory bank," at the top of the wavetable options, are not actually wavetables. They are portions of the operating program read as wavetables. They are unpredictable. There are areas of silence, areas of wild noise, and more. And, what's more, they exist in volatile memory, which is to say that they are likely to be different at different points of use.
When one of the memory banks is selected, the audio FM knob in the oscillator frequency sections (of both the Principal and Modulation oscillators) becomes a means to "move through" the operating program used as wave table. LEDs will light up next to the "fm in" knob between the words "mem" and "skew" (memory skew) indicating which wavetable channel (red or green) is using a memory bank option.
The Modulation Oscillator
The Modulation Oscillator is intended as a means to modulate the Principal Oscillator, but can be used as a typical oscillator on its own.
Tuning is achieved with the large knob, with indications of frequency surrounding it for both its audio frequency ("high") and low-frequency (low) settings. There is also a "fine tune" trim available.
There are two jacks that provide external modulation of the oscillator frequency: one audio jack for audio frequency modulation with a dedicated knob, and one banana jack for control voltage frequency modulation with a dedicated attenuverter.
The green "RANGE" knob allows you to choose which frequency range you want the oscillator to operate within. There are three options:
"low": This option sets the oscillator to output frequencies between .25Hz and 64Hz, and is intended for "low frequency oscillator" application.
"high": This option is the audio-range oscillator option, and has a frequency range of 27.5Hz to 7040Hz.
"pitch track": In this setting, the frequency of the Modulation Oscillator follows the frequency changes of the Principal Oscillator. To achieve tracking without an offset, set the Modulation Oscillator to 440Hz.
The "SHAPE" button allows you to choose the oscillator waveform output. You may select between a sawtooth, a square, and a triangle wave.
MOD TYPE / MODULATION INDEX
The Modulation Oscillator is designed to provide modulation for the Principal Oscilator. The Mod Type section allows you to select three types of modulation, and combinations of those selections.
Selecting Morph as a modulation destination for the Modulation Oscillator allows the Modulation Oscillator to modulate the Morph function on the Principal Oscillator. The waveform output of the Modulation Oscillator will cause movement back and forth between the green wavetable selection and the red wavetable selection made on the Principal Oscillator. Having the Morph knob turned fully left will result in the largest range of modulation.
Selecting Warp as the modulation destination for the Modulation Oscillator will result in the Modulation Oscillator's modulation of the amplitude of the sine wave output by the Principal Oscillator. Having the Warp knob turned fully left will result in the largest range of modulation.
Selecting "ptch" (Pitch) as the modulation destination for the Modulation Oscillator will result in the Modulation Oscillator modulating the pitch of the Principal Oscillator.
The Modulation Index section controls the amount of the modulation sent to the Principal Oscillator from the Modulation Oscillator. The numbered knob controls the amount in general. The attenuvertor allows you to modulate the amount with an external voltage source.
MIDI / prin / SYNC
A grey button in the upper left side of the 259e allows you to select two types of oscillator sync, as well as MIDI note-on sync. "Soft" uses a phase-locked loop to achieve synchronization. "Hard" sync truncates the waveform to achieve synchronization. MIDI syncs to MIDI note-on messages.
Internal Bus Messages
As with several other Buchla modules, DIP switches on the back of the module allow you to select one of the internal busses upon which the 259e can receive MIDI messages. The module must be remote-enabled in order to achieve this.
The 259e decodes the pitch (MIDI note number) contained in note-on messages originating from a 225e, 226h, or 218e arriving on its selected channel of the internal bus. It also responds to pitch bend messages.
Setting the Internal Bus I.D. Number
The Internal Bus I.D. number for the module is set with two DIP switches on the back of the module. Settings can be for A,B,C, or D. Change the DIP switch settings, shut down and reboot the module, and hold remote enable button for two seconds to display your changes on the 225e Preset Manager screen.
It is most useful if each oscillator in a system has its own Internal Bus I.D. number.
Potentiometer Calibration
While the process is typically unneeded, there is a calibration procedure for the 259e's input potentiometers. It eliminates the slight dependency of frequency versus knob setting for both the f.m. modulation knobs and the c.v. multiplier knobs. If you think your multiplier knobs may not be tracking correctly, you can employ this factory calibration procedure and it may fix the problem.
- Turn all knobs counter clock-wise (CCW) – except principal OSC set to 220.
- Hold 'midi sync' button whilst you power on boat.
- Hold for 5 seconds and then release.
- There should be a constant tone generating from the 259e. After a few seconds there will be a brief drop in the sound from the tone; this means calibration has been successful.
Revision Note
259e Revision 4 and below were called the "259e Complex Waveform Generator." In place of the current a, b, and c "memory banks," there were wavetables 6, 7, and 8. Revision 5 and above introduced the "memory bank" wavetables.
Remote Enable Storing knob settings is also made possible when the module is remote enabled. As in all 200e series modules, the settings of pots and switches can be locally stored and subsequently recalled by the preset manager such as models 225e or 206e.
To connect or disconnect the module from the central library function, push the remote enable button. A red LED signifies a connection.