The OB-X and OB-Xa Analog Synths

Oberheim OB-X Synth

Oberheim OB-Xa Synth

8 Voices of legend

Imagine combining 8 mono synths to create a massive, authentic analog sound! This unique sound is born from the subtle variations and imperfections across each voice card. Certain electronic components, especially those in the classic OB-X circuits, introduce rich layers of harmonic distortion at various points—from the filters and VCA to the output stage. OB-Xtreme focuses specifically on recreating these imperfections, with a special emphasis on delivering that signature "Growl" at the output stage.

Now introducing OB-Xtreme V3, the latest evolution in the OB-Xtreme series. While OB-Xtreme 1 was a simpler, streamlined interpretation of the OB voice card architecture, V2 refined this approach, staying true to the specifications and feel of the original OB-X and OB-Xa designs.
V3 takes the synthesis experience further, delivering new features and significant improvements while maintaining preset compatibility with V2.0, and is offered as a complimentary upgrade for all existing V2 users.

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Main Features

Below is a summary of the OB-Xtreme 3.0 features. In essence, OB-Xtreme functions as an 8-voice polyphonic, 8-voice unison mono, or true mono synth. The Unison mode adds a rich, thick texture by enabling polyphonic unison, which offers a powerful 8x8 voice configuration with adjustable voice clones (configurable as 1, 3, or 7 clones per voice).

Core OB-X/OB-Xa features are faithfully included, with SAW, PULSE, and TRI oscillator shapes, as well as the unique SAW+PULSE combination, which can add an extra octave harmonic based on the pulse width setting.

Filter options include a 2-pole and a 4-pole mode: The 2-pole filter, based on the OB-X, provides the smooth, resonant SVF (State Variable Filter) response, while the 4-pole filter, modeled after the CEM3320, offers a Moog-like resonance at lower cutoff values. High-pass and band-pass outputs are available in 2-pole mode, along with an optional filter "bleed" for added authenticity.

The Xtreme Factor control manages emulated OTA-induced distortion, particularly the classic CA3080 chip distortion used throughout the OB-series circuits. Users can push these settings beyond the original specifications for more aggressive tones or stay within traditional limits for a classic OB sound. Both PRE and POST distortion circuits can be bypassed independently for flexibility, with PRE affecting lower notes and POST acting linearly across the range.

Additionally, OB-Xtreme offers under-the-hood controls for fine-tuning the voltage offsets of each voice card, which is essential for replicating authentic analog character. This approach uses Virtual Component Modeling (VCM) to mimic analog nuances effectively without excessive setup time. Seven macro sliders provide quick access to these settings:

OB-Xtreme 3 voice cards

  • OSC (SPREAD): Controls tuning offsets for oscillators 1 and 2.
  • FILT: Adjusts filter envelope offsets.
  • AMP: Sets amplitude envelope offsets.
  • VCF: Modifies VCF deviation.
  • PW: Controls pulse width offsets.
  • PORT: Sets portamento glide time lag.
  • XMOD: Adjusts cross modulation offsets.

You can apply small random deviations per note in real-time or scatter them across all eight voices. These voltage offsets are visually represented in the interface with positive or negative voltages (yellow/blue), making it easy to see adjustments. Tuning individual cards in semitone steps (up to +1 OCT) opens creative possibilities like a pseudo-chord mode when using Unison mode.

All manufacturer and product names mentioned on this page are trademarks of their respective owners, which are in no way associated or affiliated with ALYJAMESLAB. The trademarks of other manufacturers are used solely to identify the products of those manufacturers whose tones and sounds were studied during ALYJAMESLAB sound development. All names of instrument and inventors have been included for illustrative and educational purposes only and do not suggest any affiliation or endorsement of OB-Xtreme by any company or instrument inventor

OB-Xtreme Videos

spans from early version 1.0, 2.0 and upcoming version 3.0 (coming up)

Product Demos by Aly james

OB-Xtreme Features and Details

  • Cross-platform 64-bit capability (PC VST3 and Mac VST3, AU (Audio Unit)).
  • 64-bit build using the latest OS and IDEs (PC: Visual Studio, Mac: Xcode).
  • Updated high-resolution, DPI-aware GUI (graphic interface).
  • Refined and rewritten sound engine for enhanced performance.
  • 8 or 4-voice with polyphonic or mono unison with per-voice pan control and global stereo widening, supporting single-voice mono and polyphonic unison (8x8).
  • Comprehensive OB-X/OB-Xa functionality, including oscillator shapes, X-MOD, F-ENV, SYNC, with expanded modulation routing options.
  • Enhanced oscillators and filter modes: 2-Pole/4-Pole LowPass and 2-Pole HighPass & BandPass, based on OB 2-Pole SVF and CEM 3320 24Db.
  • Accurate SAW + PULSE oscillator mixing, generating a +1 octave harmonic depending on pulse width settings.
  • Up to x16 oversampling for cleaner, higher-quality audio.
  • PRE and POST OTA (CA3080 chip for VCA, Filter, and Output Stage) with adjustable distortion (Xtreme Factor) and bypass options.
  • Seven macro controls manage voltage offsets and deviations across all 8 voice cards, with options for random propagation and real-time per-note deviation.
  • Legacy filter modulation and EG/VCA modes enable compatibility with V1 sounds; default envelope/VCA uses the CEM3310/CA3080 combo (linear VCA and exponential envelopes), while legacy mode offers ultra-snappy response.
  • Dedicated Vibrato LFO, original LFO + additional LFO 2, with phase reverse for LFO 1 & 2 (cards 1, 3, 5, 7), and optional keytracking inversion.
  • Gate re-triggering for LFOs, featuring SINE, RAMP, PULSE, SAW, TRI, S&H, and Noise waveforms. LFO 2 can BPM sync or act as a one-shot ramp envelope (up or down).
  • Single or multi-LFO modes: one global LFO or one per voice card.
  • Optional VCF bleed effect.
  • Sustain pedal options: standard or OB Mode (sustain like piano) with controllable envelope release offset.
  • Keyboard Scaling (KBS) enables master level blending between presets from two OB-Xtreme instances or patching to LFO's modulations.
  • Built-in preset browser with categorized organization for easy navigation.
  • Switchable OB-X (light mode) and OB-Xa (dark mode) skins for visual variety.
  • New PC VST3 and Mac VST3 AU with native support for Silicon (Universal Silicon/Intel compatibility).
  • Completely remade high-resolution, DPI-aware GUI with vector knobs, improved graphics and functionality.
  • Refined sound engine with selectable polyphony (4 or 8 voices) and configurable mono and poly unison modes (2, 4, or 8 clones).
  • New global stereo panning presets, including Wide, Spread, Ping Pong, with selectable panning power law.
  • Expanded modulation options: velocity can now modulate filter or amp envelope decay, and XMOD can patch to filter modulation.
  • Added 2-Pole HighPass output with filter bleed; 4-Pole volume compensation now automatically applied.
  • Up to x16 refined oversampling for optimized CPU performance.
  • Enhanced POST and PRE OTA (CA3080 chip for VCA, Filter, and Output Stage) variable distortion (Xtreme Factor) with maximum gain doubled.
  • Envelope scope now visualizes filter or amplitude envelopes when parameters are adjusted.
  • New Keyboard Scaling (KBS) feature allows configurable keyboard voltage tracking, assignable to master volume or LFO modulation depths.
  • Improved user experience with altGr + click reset on knobs, skin setting recall, and more.

ABOUT THE XTREME FACTOR AND CARDS VOLTAGE OFFSETS: "The Beauty and The Dirt"

In the world of analog synthesizers, imperfections aren’t merely tolerated—they’re celebrated. They breathe life into sounds, creating textures that digital systems struggle to emulate. OB-Xtreme embraces this philosophy fully, bringing vintage-inspired warmth and complexity into the digital realm with its Xtreme Factor and customizable voltage offsets for each voice card. These two features together represent the heart of OB-Xtreme’s sonic character, where “the beauty and the dirt” of analog synthesis intersect to produce something truly unique. Nothing is like 8x8 voices drifting with portamento.

The Xtreme Factor: A Gateway to Analog Grit

The Xtreme Factor in OB-Xtreme is a highly expressive control that emulates OTA (Operational Transconductance Amplifier)-induced distortion, a key ingredient in the legendary sound of classic synths like the Oberheim OB-X. In real analog circuits, OTAs such as the CA3080 are found at various points in the signal path, including the filter, VCA, and output stages. As these components process audio signals, they inherently introduce harmonic saturation and distortion, shaping the sound in ways that feel organic and musical. By modeling this distortion digitally, the Xtreme Factor control lets users dial in anything from subtle saturation to extreme distortion, granting a vast range of tonal possibilities.

This control is not just about adding loudness or fuzz—it’s about emulating the depth and complexity of analog warmth. When the Xtreme Factor is engaged, it can add a hint of growl or push the sound into a rich, aggressive territory. The beauty of the Xtreme Factor lies in its ability to give each voice a different level of character; set it to a minimum for clean, traditional tones, or push it beyond original specs for something truly “XTREME.” By enabling both PRE and POST distortion circuits to be used independently, OB-Xtreme offers even more versatility. PRE distortion affects the lower register more heavily, while POST distortion applies evenly across the entire range, giving users granular control over the kind of saturation they want.

Voltage Offsets: The Subtle Art of Voice Card Variation

A fundamental part of analog synthesis is the natural variation in pitch, filter response, and envelope timing that occurs between voice cards. In the original OB synths, each voice card was like an individual personality, with slight imperfections that gave each note a unique character. OB-Xtreme’s voltage offset controls allow users to replicate this organic quality by introducing variability across the eight voice cards. By adjusting offsets, users can create intentional inconsistencies in tuning, filter envelope offsets, pulse width modulation, and more, crafting a soundscape that feels “alive” rather than sterile.

Voltage offsets represent the beauty of analog error—a microcosmic reminder of why analog sounds are beloved for their richness and unpredictability. When voltage offsets are applied, the result is subtle but incredibly impactful: a chorus-like effect, delicate detuning, or a slight shift in modulation that adds dimension to the overall sound. For example, by adjusting the oscillator spread (tuning offsets for OSC 1 and OSC 2), OB-Xtreme can mimic the slight drift found in real analog oscillators, which helps create a sound that feels both rich and vintage.

Try increasing the Spread parameter with 8 unison clones and you are reaching super chorus territory.

The Beauty of Imperfection

When combined, the Xtreme Factor and voltage offsets offer users the best of both worlds: control and character. Together, they bring the beauty and the dirt to life, creating sounds that are both polished and raw, modern yet vintage. This combination of warmth and unpredictability is the essence of OB-Xtreme’s appeal, allowing users to push digital synthesis into an expressive, almost organic realm. Each note can carry its own story, oscillating between clear, pristine tones and gritty, distorted textures.

In practical terms, these features make OB-Xtreme an invaluable tool for producers who crave analog authenticity. The Xtreme Factor provides a way to blend dirt into the sound at will, while voltage offsets give each voice a touch of individuality. Together, they create a deeply satisfying synthesis experience, where perfection is found not in uniformity, but in diversity—the way each voice dances, imperfectly yet beautifully, in harmony with the others.

In OB-Xtreme, the beauty and the dirt are more than just sound—they’re a philosophy. By embracing and celebrating these imperfections, OB-Xtreme opens a door to a more expressive, character-driven approach to synthesis.

  • : Windows 10 and higher
    PC: 64bit VST3 compatible host.
    Not supported but has been proved to work on Windows 7
  • : Mac OS 10.14 and higher (64bit)
    Mac: 64bit VST3 or Audio-Unit compatible host.
    Universal 2 binary: works natively on both Silicon and Intel based Mac.
    Not supported but has been proved to work down to Mac OS 10.10


  • Protools: Avid Protools only supports its proprieratary format AAX at the moment but you can still easily load an AU or VST plugin with the help of a VST/AU host plugin, some popular solutions are DDMF Metaplugin or BlueCat's Patchworks, others might be available that I am not aware of yet.

OB-Xtreme 3 Manual

Get amazing details about OB-Xtreme!

OB-Xtreme V3 Manual - coming up!

OB-Xtreme 3 User Manual


Change Log

You can check your current version with a right-click on the GUI.
Updates for OB-Xtreme 2.0 owners are free until version 4.0.

pending - v3.0.1
  • Fix - MIDI Learned/assigned controls are now correctly saved with custom presets.
  • Changed - increase OSC tuning ranges to -39 +39 semitones in order to have 0 st visually centered.
  • makes more sense for most users and also make 0st at MIDI value 64.

11/18/24 - v3.0.0
  • Introducing - Mac VST3 and Native Silicon (M1/M2, etc.). Builds are "Universal 2," meaning both VST3 and AU work natively on Intel x86-64 and ARM64 Apple Silicon Macs.
  • Introducing - Fully remade high-resolution GUI with vectorized knobs and buttons for improved clarity.
  • Added - Enhanced sound engine with selectable polyphony (4 or 8 voices) and configurable mono/poly unison modes (2, 4, or 8 clones).
    Useful for reducing CPU usage.
  • Added - 2-Pole VCF HighPass output and optional VCF Bleed.
  • Added - New parameters: velocity to VCF and amplitude envelope decay times.
  • Added - New parameter: Global Velocity Response.
  • Added - Panning internal presets for quick stereo placement (Wide, Spread, Ping Pong, etc.).
  • Added - XMOD oscillator output can now be patched to VCF frequency.
  • Added - Real-time filter and amplitude envelope visualization.
    Particularly useful when switching EG VCA modes to observe envelope and VCA changes.
  • Changed - OTA maximum possible gain increased by 100%.
  • Changed - OSC1 & 2 tunings range increased (- 36 to + 39 semitones).
  • Changed - 4-Pole volume compensation now applied automatically.
  • Added - Keyboard Scaling (KBS) for configurable keyboard voltage tracking, assignable to master volume or LFO modulation depths.
    Ideal for balancing volume across octaves or crossfading with two plugin instances for preset blending (e.g., bass on the left, stabs on the right). Can also be applied to LFO modulation depths.
  • Improvements - Knobs can be reset with AltGr + click, skin settings are saved and recalled, knobs and sliders respond to mousewheel.
  • Fix - PWM now receives full LFO range (voltage polarity fix).
  • Fix - OSC phase no longer resets on waveform change.
    Eliminating initial loud sound until normal drift resumes -phase initialization fix.
  • Fix - Resolved rare crash with legacy MIDI Program Change.
  • Fix - Optimized CPU usage.
  • Fix - Improved VST3 MIDI support.

11/19/22 - v2.0.2
  • fix- GUI OSC Tuning knobs: no more dead spots and perfect sync
  • fix- GUI Cards OSC Deviation indicators: now update voltages even if not playing
  • OSC Tuning in semitone now displays over OSC's tune knobs when clicked or turned
  • Little CPU reduction

09/29/22 - v2.0.1 release
  • Add v2 factory presets, activate LFO2
  • LFO2 Modes (LFO, BPM Synced, One-Shot Envelope)
  • LFO2 modulation and routing activated (SPREAD, WIDTH, MIX2, MIX3 etc..)
  • Add semi-tones tuning per voice card
  • Vibrato delay time corrected
  • Added preset nav < -> arrows on the main panel
  • Add Portamento voltage offsets and Glissando mode
  • Add XMOD voltage offsets
  • DC filter (20 - 50Hz) control is now available for the end user adjustment (can tame low-end)
  • Re-worked CARDS panel controls
  • Most parameters are now automatable and save state
  • fix- Pitch-Wheel voltage going down briefly when selecting OSC2 ONLY until next trigger
  • fix- EG attack stages now receive voltage offsets correctly
  • fix- wrong LFO voltage on PWM 2
  • fix- GUI filter modes buttons logic now reflect setting (band-pass is only available for the 2Pole SVF)
  • fix- Corrected V1 Presets using wrong legacy settings
  • fix- Corrected LFO S&H rate (was half-time)
  • Code tidy minor CPU reduction
  • HD mode setting is no more reset by preset loading/changing
  • Place holder for a future 4 steps modulation sequencer or whatever it will become

07/16/22 - v2.0.0 pre-release (only missing v2 factory presets and LFO2 not active)
  • Cross Platform 64bit capability (Windows VST3 and Mac AU(Audiounit).
  • 64bit build using latest OS and IDE(PC VisualStudio and Mac Xcode).
  • Updated GUI(graphic Interface) also now using high-res graphics and DPI awareness.
  • Rewritten and Refined sound engine.
  • 8 voices poly or mono unison with per voice PAN control and global stereo widening control, can also turn into real (one voice) mono or act as polyphonic unison (8x8).
  • Most of OB-X/OB-Xa functions added (OSC shapes, X-MOD, F-ENV, SYNC etc) on top of new modulation routing.
  • Enhanced oscillators spectrum and filter modes (2Pole/4Pole LowPass and 2Pole BandPass) based on OB 2pole SVF and CEM 3320 24Db, 4Pole can have an optional volume compensation.
  • Accurate SAW + PULSE OSC mixing (can produce +1 octave harmonic depending on the pulse width).
  • Up to x32 oversampling.
  • POST and PRE OTA (CA3080 chip used for VCA, Filter and Output Stage) variable distortion (Xtreme factor) with bypass.
  • x8 Voice cards voltage offsets and deviation can now be controlled easily by five macro controls, optional random propagation and realtime deviation (per note).
  • Legacy modes for Filter modulation and EG/VCA shapes to match V1 sounds and behavior if needed, the default envelope/VCA behavior is the CEM3310/CA3080 combo (Linear VCA and exponential envelopes) while the legacy mode can be used for more snappy sounds (using an ultra exp VCA response).
  • Vibrato LFO, original LFO + additional LFO 2, Phase reverse option mode for LFO (card 1,3,5,7) got phase reversed modulations, can also invert Keytracking.
  • LFOs have gate re-triggering option, SINE, RAMP, PULSE, SAW, TRI, S&H and Noise shapes, LFO2 can be BPM synced.
  • LFO can be set to single: one LFO on the main board for all voice cards or to multi: one LFO per card
  • Optional OB-X 6bit resolution on the Filter Cutoff knob scanning.
  • Sustain pedal can act normally or use the OB Mode (sustain like piano) controllable Envelope Release offset.
  • (Mac) Introducing new Mac Signed and Notarized Installers.
  • Basic internal preset browser with main categories.
  • OB-X (light mode) or OB-Xa (dark mode) changeable skins.
10/05/14 - v1.1
  • Small bug fix
10/01/14 - v1.0
  • Initial release.

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Get OB-Xtreme 3 for PC & MAC

OB-Xtreme 3.0 comes with both PC & Mac Installers