Buchla 248t MARF Multiple Arbitrary Function Module Instructions

During the development of the MARF, we gathered information about each function from every available source. Communicating this information to users of the 248t presented a challenge: how do you clearly explain such a complex device? We determined that the most effective approach would be to provide three complementary sources of information, allowing users to cross-reference them when needed:

1. Function and Feature Reference – In the following pages you will find a detailed list of all functions and features, presented as a concise translation of the original 1977 user manual.
2. Video Manual – A comprehensive, chapter-based video guide covering all functions, programming techniques and examples. Watch the Video Manual
3. Original 1977 User Manual – Written by Buchla & Associates. Although extremely comprehensive, this manual reflects certain historical differences—for example, voltage scaling (original Buchla systems use 2.4V/Octave, while Eurorack systems use 1V/Oct). Despite these differences, it remains an excellent reference and complements the two resources listed above. Download Original 1977 User Manual

FUNCTION

Preparing Your 259t Oscillators to Host the 248tDuring MARF development, the 259t ART firmware was updated to utilize ART’s high-speed signal capability, enabling accurate pitch slides and glide effects generated by the MARF. Before integrating the MARF into your system, we recommend updating the firmware of your 259t. The update file is available for download, and installation instructions can be found in the 259t user manual.

Upon power-up, the indication LEDs on the 259t display the firmware status using the Modulator Range LEDs while the Waveshape LEDs are off:

• All Range LEDs off – update needed
• High LED on – update done

If the ART functionality on your 259t has not been used previously, initial tuning may be required. Refer to the 259t user manual for detailed instructions. The Initial Tuning and Auto Tuning switch is accessible at the lower-right section of the MARF.

Note: For optimal combined operation of the 248t and 259t seven octave range, we recommend using the 248t in half (5 octave) or limited range modes, to avoid generating notes outside the range covered by the 259t.

External Inputs CalibrationThis is usually done at the factory and is rarely needed again. If you notice an offset (e.g., 0V in doesn’t give 0V out), perform the following procedure:

• Unplug everything from inputs A–D.
• Set both function switches to STOP.
• Press the External switch 4 times (the LED will flash for approximately 2 seconds).

Calibration is complete and the offset should now be minimal or gone.

MARF Multiple Arbitrary Function Module 248t

The MARF is divided into three main sections:

• The two Function Generators (FGs) operate independently of each other and can access the 16 stages in multiple different ways.
• The Programming Section works in conjunction with the Output Voltage & Time Sliders to modify each stage’s voltage level, duration, and transition behavior.

Breakdown of the Output Voltage & Time SlidersOutput Voltage Level: The top row of sliders sets the main output voltage level in conjunction with the Output Voltage programming section per stage. Alternatively, they select which of the external input voltages (A, B, C, D) are passed through the output voltage modifier programming and out through the voltage output jacks.

Stages: The 16 LEDs along the middle represent the 16 stages, and light up when they are advanced and displayed by the FGs, or when using the Stage Number edit switch.

Interval Time: The lower row of sliders sets the interval time of each stage in conjunction with the Time Range programming section. The default time range is set from 2 seconds at the bottom of the slider to 30 seconds at the top of the slider, as indicated on the panel. The sliders also output a voltage based on their settings at the Time output on the FGs.

MARF Multiple Arbitrary Function Module 248tPresets and Quantization Scales 

The row of buttons under the 32 Voltage and Time sliders allow for storing and recalling 12 Presets, and also function to select the scale and key for any stages with Quantize enabled. Additionally, there is a button for sending an Auto-Tune message to ART-equipped oscillators.

• Loading a Preset: Press the Load button and then one of the buttons labeled 1 to 12. The settings in that memory location are immediately recalled for all 16 stages. The physical sliders are temporarily overridden until moved past the stored value.
• Saving a Preset: Press the Save button and then one of the buttons labeled 1 to 12. All stage settings, including current slider positions, are saved to non-volatile memory.
• Changing Key: Press the Key button and then one of the 12 keys (C to B).
• Changing Scale: Press the Scale button and select Major (10), Minor (11), or Chromatic (12).
• Auto Tuning: Pressing the Autotune switch once will send the tuning message to both ART outputs. Holding the switch for a few seconds sends the Initial Tune message.

MARF Multiple Arbitrary Function Module 248tOutput Pulses: Each stage can have two independent pulse outputs programmed to it. Each switch is a three-position momentary switch. Pressing the switch upward adds the pulse to the stage and lights the LED. Pressing the switch downward removes the pulse from the stage and turns the LED off.

Clear: This is a momentary switch in the down position. Pressing up clears the programming on all 16 stages: Output Pulses 1 and 2 are cleared; Output Voltage is set to Continuous, Full Range, and Internal Source; all Operating Mode settings are cleared; Time Range is set to 2 to 3 seconds; all slider values default to their current physical positions.

Stage Number: This 3-position momentary switch is used to scroll through and locate specific stages in order to edit their programming without inhibiting live FG operation.

• Flipping the switch left or right while displaying one of the FG’s functions will jump the active selection to stage 1.
• Holding the switch left or right scrolls through all stages in approximately 2–3 seconds. Pressing any programming modifier during active scrolling applies that setting globally to all 16 stages.

Voltage Programming Modifiers

Quantize/Continuous: A three-position momentary switch that defaults to the unquantized continuous voltage setting. Pressing up quantizes the voltage to a 1V/Oct scale. Pressing down removes quantization.

Sloped/Stepped: A three-position momentary switch that defaults to stepped mode. Pressing up adds slew time (based on the stage’s interval time) to the stage. Pressing down removes the slope.

Range (Full / Half / Limited): A momentary switch that defaults to full range (0–10V). Half Range restricts the output to 0–5V (approximating historical 5-octave ranges and allowing more precise pitch tuning). The five limited range switches restrict the slider output to a 2-volt span with octave offsets.

Source (External/Internal): This three-position momentary switch defaults to internal mode. In external mode, CV sources patched into inputs A, B, C, or D are routed through the voltage modifiers, and the stage’s voltage slider selects which external input is active.

Operating Mode Modifiers

Stop: Pressing up on this three-position momentary switch adds a stop modifier to the stage. When an FG reaches this stage, it will complete its interval time but will not advance further until a start pulse is received.

Sustain: Pressing up adds the sustain modifier. When a high gate is present at the start input, the FG will hold on this stage for as long as the pulse remains high.

Enable: Pressing up adds an enable modifier. The FG pauses on the stage until a voltage above 5V is applied to the start input.

Cycle (First / Last): These modifiers define loop zones. The FGs begin playback at the stage marked First and loop back to it immediately after completing the stage marked Last.

Time Programming & External Inputs

Time Range Switches: Four momentary switches select the baseline interval time range, from fast transient speeds (.002 seconds) up to long cycles (2 minutes).

Source (External/Internal): A three-position momentary switch. Internal mode uses the sliders and time range switches. External mode routes CV sources patched into A, B, C, or D to control the interval time of the stage.

Four External CV Input Jacks (A, B, C, D): Allow external control voltages to determine stage timing or represent processed signals through the voltage modifiers. If a stage is configured for external time and no CV is present, the interval time defaults to the fastest value of the active range.

Outputs, Indicators & MultipliersART Output (Black Jack): Outputs a high-speed digital signal for pitch control based on the active stage sliders and modifiers. Connect this to the 259t ART input and configure the oscillator to ART mode. Use the selector switch above the outputs to route the gate source from Pulse 1, Pulse 2, or ALL stages.

Voltage Output (Blue Jack): Outputs standard CV based on the active stage configuration. This output tracks at 1V/Oct when quantization is enabled.

Time Output (Blue Jack): Generates a CV proportional to the current stage’s interval time. This can function as a secondary modulation source independent of the active stage timing when set to External Time mode.

Programmed Pulse Outputs (Red Jacks): Two independent jacks that fire gates exclusively on stages programmed with active Pulse 1 or Pulse 2 assignments.

Output LEDs (Red): Visual indicators displaying active gate activity on the respective pulse busses.

Reference Output (Purple Jack): Provides a downward ramp voltage spanning the exact duration of the active stage; ideal for driving a 292t LPG directly without requiring an intermediate envelope generator.

All Pulses Output (Red Jack): Fires a trigger pulse at every step transition. Useful as a master clock out.

Time MultiplierA global time multiplier knob and CV attenuverter allow stage times to be scaled dynamically from half-time (0.5x) to four times (4x) longer.

Function Generator Controls & Address Modes

Mode Controls

Advance: Manually advances the Function Generator to the next active step.

Start / Stop: Intercepts and controls the execution of the internal sequencer clock manually or via patch cable input pulses.

Status LEDs

• Green (Run): Internal clock is running and advancing stages.
• Yellow (Hold): Advance sequence is paused, waiting for a valid Start input condition (active on Sustain or Enable modifiers).
• Red (Stop): Clock sequence is stopped via control input commands, a programmed Stop modifier, or when Stage Address is set to Continuous.

Stage AddressReset (Two-position momentary): Immediately returns the Function Generator to the step assigned as First. If no loop first marker exists, it resets to Stage 1.
Display (Two-position momentary): Previews the current stage configuration internally on the LED indicators without interrupting sequence playback.
Display LED: Confirms which active Function Generator is currently routed to the programming display panel.
Cont / Strobe (Three-position): Continuous sweeps manually through stages via the Address control dial and stops the internal clock. Strobe immediately snaps to the step corresponding to the active Stage Address input value.
Internal/External: Determines whether step location is routed to the manual panel knob or controlled via CV signal input.