Oberheim OB-X Synth

8 Voices of legend

What happens when you take 8 separate monophonic synths and use them together? Huge analog sound! This is caused by the slight imperfections between each voice card fine tuning.

This was a classic analog synthesizer available in many voice configurations, featuring a SEM Filter with its own ADSR, a VCA with ADSR, a flexible LFO and others goodies, this synth has been used by Herbie Hancock, Prince, Chick Corea, Cirrus, Depeche Mode, Queen, Supertramp, Kenny Kirkland, Jean-Michel Jarre, Van Halen, Tangerine Dream, Rush, Simple Minds, Chicago, Styx, Ultravox and dozens more!

OB-XTREME started out as a simple VST striving for that classic OB Brass sound, stripped down to the minimum, then I thought about how I could bring more "warm" into a digital VA synth and what features I could add to the original design.

So, based on an original OB-X architecture, I have crafted some controllable diode clipping stage before and after the filter, which really brings body and harmonics for a beefy result, especially in conjunction with the VCF...It can be soft and warm or scream in a good way. From there I extended the concept.

Contrary to all my others VSTis, OB-Xtreme is not an exact recreation of an OB-X, it is rather a "closely inspired by" approach, stripped down to the minimum for an easy sound design of OB Brass, Pads, Leads, FX and Percussions. However, some extended features like an optional FAT mode and Multiple DAW outputs per voice can push you into experimental mood...different FX treatments per voice...

The OB-XTREME VST, based on the OB-X Analog character and design, offers:

The classic detuning between voices , SEM based VCF configured as a 2 poles State variable filter, Snappy VCAs, 8 Voices with unison or polyphonic control, a FAT mode (polyphonic unison), 2 sawtooth oscillators per voice with SYNC function, a special pitch LFO with many shapes including noise, 2 stages of virtual analog saturation before and after the filter with an optional CLEAN mode which disables the last stage for a cleaner sounding filter, panoramic control for each voice and separate outputs before the filter stage for mixing experimentations, Portamento (mono) and auto-glide (polyphonic), velocity modulation and of course full MIDI learn.
You will obtain that legendary powerful analog warm! Funk it up with some Brass Stabs, cutting leads, lush pads and screaming bass.

OB-XTREME provides optional separate outputs per voice for your DAW before the filter stage! So you can experiment things like different treatments for each note of a chord, use different filter per voice, reverb settings etc...It will make great results.

Get OBXtreme!

OBXtreme VST

OBXtreme VST Videos & Sounds Demos Playlists.

The Fat and screaming sound!

OBXtreme OB-X Lite VST Features and Details


This is the main feature here, Analog warm...One of those real world analog techniques is for example a Diode Clipping that will generate mostly third harmonic with a smaller amount of fifth, and lesser amounts of each additional higher odd-order harmonic. If a sound containing rich harmonic content like a digital saw oscillator is feeding a filter with a slightly saturated content it really gives the bass a nastier pleasant sound.
Basically the XTREME knob will turn a saw tooth into an almost square wave at middle setting and goes crazy at full.
A second stage is also present AFTER the filter stage so the filter resonance can really overload at higher settings. The second stage can be disabled for more headroom and cleaner sounding filter if needed.


Each voices slight detuning is controlled by the SPREAD knob, this really gives the characteristic OB sound, with phase masking around the stereo field, when used in conjunction with the FAT mode it can almost sound like a "supersaw" at max detuning...The iconic SYNC oscillators sound can be activated and by only modulating the OSC 2 pitch with the LFO you are in cutting lead solo territory! Although OB-XTREME do not feature a noise source nor the pulse OSC (which might be added later) some square sounding harmonics can be achieved with the XTREME saturation. You can trigger the 8 voices in polyphony or in mono (8 voices unison), the FAT mode is basically a huge polyphonic unison which gives the digital VSTi an even warmer analog feel.

SEM Filter

A classic resonant 12Db/Oct State Variable filter is used with its own ADSR, the LOW end is absolutely not filtered which means that it is up to you to decide if you want the huge bottom or not, which is not often the case in VSTis. The sound of an overdriven filter is really different than a clean sounding one; OB-XTREME gives you the choice.

LFO Vibrato and FX modulation

The LFO is rather simple in its routing; modulate OSC2 or OSC2 + OSC1 pitch. However it features a SYNC option and many shapes including NOISE which opens up to some interesting sounds, some presets like analog claps or gunshots are possible.


The OB-XTREME has separate outputs for every voice before the filter stage.

You can choose from ALL to 1 Stereo Channel or Separate Channels for each voice.


Even if the design is simple and stripped down, velocity can also be assigned to the VCF cutoff frequency.


The GUI features all the OB-XTREME controls, most of the parameters can be MIDI learned and controlled by an external MIDI Hardware or automation which gives you far more control and expression.


(Additional technical info are in the manual.)

Fully discrete design based, an OB-X card featured a variant of the SEM Filter chip which is different than the CEM chips used on the OB-Xa, the CEM VCA chips are the same.

Each voice can be fine-tuned in addition to the auto tune function of the synthesizer.

The others synths at that time often used a 4-pole (24dB/Oct) filter instead which has a steeper roll-off and then a different sound.

OB-X Voice Card

Analogue warmth seems to be the Holy Grail in these digital days. But why does it hold such appeal, what does it do the sound?

As I was working on a new OBERHEIM OB-X emulation tailored to my musical needs, I thought about bringing into the party some analog code I have made earlier for the VSDSX VST (Simmons Drum Synth accurate emulation) and start tweaking on it...this really brings some extended harmonics and compression to the sound.

Later I decided to push the volume hard into saturation territory before and after the SEM filter stages...This was very nasty sounding and it becomes the main extended feature of OB-Xtreme VST...You can push it hard :)

If you stay gentle on the volume, this is a part of what is so called "warmth" sounding.

Analog world is not perfect, vintage electronics components aren't either.

Humans ears like more what is not perfect, this is a fact.

The tape is also a good example of pleasant saturation and high frequencies compression.

Ton of parameters are in effect in an analog system which induce a lot of non-linear modulations to the sound.

One of those effects is for example a Diode Clipping that will generate mostly third harmonic with a smaller amount of fifth and lesser amounts of each additional higher odd-order harmonic. If a sound containing rich harmonic content like a digital saw oscillator is feeding a filter with a slightly saturated content it really gives the bass a nastier pleasant sound.

Look at what a diode clipping does to a sine wave depending on the volume...

Diode Clipping

Read the OBXtreme Manual


For now there is a quick overview that should get you started!


OBXtreme User Manual

Change Log

Update History

You can check your current version with a right click on the GUI.
Updates for OBXtreme VST are worth an additional donation of your choice though they can be considered free until version 2.0, so drop me a mail request and keep in mind that they are compiled on a per user basis and it takes time.

  • - Small bug fix.

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Get OBXtreme for Windows

OBXtreme will be ported to Native x64 and OSX in the future.