Tiptop Audio Buchla 258t
Classic Buchla dual VCO with voltage-controlled waveshaping and FM
18 HP Eurorack module
The Buchla 258t is a Eurorack adaptation of the classic Buchla 200 series dual oscillator, featuring two fully independent voltage-controlled oscillators spanning 5 Hz to 20 kHz without range switching. Each oscillator offers voltage-controlled waveshaping, a processing input attenuverter for pitch scaling and inversion, and FM inputs, delivering everything from pure sine waves to saws and squares with the warmth and stability characteristic of Buchla's original analog designs. The module excels at clangorous, bell-like tones rich in non-harmonic partials as well as smooth, low-distortion sine waves, making it equally suited to melodic and timbral sound design.
Features
- Two fully independent voltage-controlled oscillators
- Frequency range: 5 Hz to 20 kHz with no range switching
- OSC1 waveshape: voltage-controlled sine to sawtooth
- OSC2 waveshape: voltage-controlled sine to square
- Processing input attenuverter for pitch scaling, compression, expansion, and inversion on each oscillator
- 1V/oct CV input on each oscillator
- Frequency modulation (FM) input on each oscillator
- Waveshape control CV input on each oscillator
- Low sine wave harmonic content
- Negligible settling error
- High short and long-term stability with rapidly changing ambient temperatures
- Back-panel trimmers: 1V/oct tracking, SHAPE (sine purity), VC WAVE SHAPE (waveshaper CV response) per oscillator
Controls & Jacks (33)
- OSC2_FREQ_Knob — Coarse frequency control spanning 5 Hz to 20 kHz
- OSC1_FREQ_Knob — Coarse frequency control spanning 5 Hz to 20 kHz
- OSC1_1VOct_Input — Fine frequency tuning control for oscillator 2
- OSC2_FM_Knob — Attenuator for FM input depth on oscillator 2, controls vibrato depth or FM intensity
- OSC1_Output — Coarse frequency control spanning 5 Hz to 20 kHz
- OSC1_FM_Input — Sets desired range of incoming control voltage for expansion, compression and inversion
- OSC1_Fine_Knob 1 — Manual control for waveshape variation from sine to square
- OSC1_Fine_Knob 2 — Fine frequency tuning control for oscillator 1
- OSC2_Waveshape_Control_Input — input cv
- OSC2_Waveshape_Control_Input — Voltage control for waveshape of oscillator 2
- OSC1_Waveshape_Control_Input 2 — Voltage control for waveshape of oscillator 1
- FINE
- OSC2_FM_Input — Frequency modulation input for oscillator 2
- OSC2_Output — Audio output of oscillator 2
- OSC2_1VOct_Input 2 — 1V/octave control voltage input for oscillator 2
- OSC1_FM_Knob — Attenuator for FM input depth on oscillator 1, controls vibrato depth or FM intensity
- OSC1_Waveshape_Knob — Manual control for waveshape variation from sine to sawtooth
- OSC1_Output audio
- Processing Input
- Processing Input
- OSC1_Coarse_Knob — Coarse frequency control spanning 5 Hz to 20 kHz
- OSC2_Processing_Control_Knob — Sets desired range of incoming control voltage for expansion, compression and inversion
- M
- MODEL
- OSC1_Processing_Knob — Sets desired range of incoming control voltage for expansion, compression and inversion
- OSC2_Fine_Knob — Fine frequency tuning control for oscillator 2
- OSC2_Processing_Knob — Sets desired range of incoming control voltage for expansion, compression and inversion
- OSC2_Waveshape_Knob — Manual control for waveshape variation from sine to square
- OSC1_Waveshape_Control_Input 1 — Audio output of oscillator 1
- OSC1_Processing_Input 1 — Audio output of oscillator 2
- OSC1_Processing_Input 2 — Processing control attenuverter input for oscillator 1
- OSC2_1VOct_Input 1 — 1V/octave control voltage input for oscillator 1
- OSC2_Processing_Input — Processing control attenuverter input for oscillator 2
How-To Guides
- Tuning a Pure Sine Wave
- Clangorous Bell Tones via FM
- Smooth Vibrato with FM
- Voltage-Controlled Timbre Sweep
- Inverted Pitch CV for Mirror Intervals
- Detuned Dual Oscillator Pad
- Sub-Audio LFO Modulation Source
- Percussive Timbre Click with Envelope on Waveshape
- Two-Operator FM Bass
Explore the interactive Buchla 258t panel on BleepDex — tap any control to learn what it does.
