Synapse Audio Obsession Review


Today we are taking a closer look at Obsession, the long-awaited Oberheim OB-Xa synthesizer emulation in the form of a VST plugin developed by Synapse Audio.

I try not to get too worked up over emulations of vintage analog synthesizers since I feel that the vintage emulation thing has been done to death. However, I was so impressed by Synapse Audio’s “The Legend,” a virtual synthesizer inspired by the Moog Model D, that I knew they would do something really special here.

I don’t have any personal experience with Oberheim’s OB-Xa, released in December 1980. That said, friends of mine with intimate knowledge of the original hardware tell me that the Obsession softsynth is arguably the closest thing to the real experience, at least in terms of its overall character. Obsession doesn’t pretend to be a straight-up emulation of the original OB-Xa, but rather a modern interpretation of it focused on the multi-voice architecture and analog modeling of the temperature-dependent fluctuations of the Curtis CEM3340 VCO chips.

The first thing you’ll notice about Obsession when you fire it up is the unabashed warmth and phatness of it, produced by several independent parameters in the Voice Edit Section that allow you to create “slop” by offsetting the front panel controls on a per-voice basis. If you right-click anywhere on the interface and then select “Randomize Voice Adjustments” in the hidden drop-down menu, these controls or “trimmers” are adjusted arbitrarily to help you avoid fiddling with them for hours on end.

The “Organic” control on the back panel in the “Global” section will randomly modulate these controls in all voices, simulating the tuning instabilities and temperature-sensitive behavior that happens whenever analog components overheat. This is where all the magic happens, especially when you switch on the “VCA Sat” button that enables the amplifier’s saturation to add a little extra mojo to your sounds.

On the front panel, you have pretty much everything you’d expect from any standard-issue virtual analog synth: Two VCOs, each with saw, triangle, and pulse waveform shapes with independent PWM. Basic ADSR amp and filter envelopes. A 12 dB per-octave filter with optional bandpass and 4-pole models and a series of buttons for oscillator mixing, white noise, and 100% keytracking of the filter frequency, which you can fine-tune with a “Constant” within the generous 6-slot modulation matrix.

On the back panel, you have two separate Step Editors with as many as 128 steps available as step modes for each of the two LFOs, enabling you to create tempo-synced rhythms or even draw in your custom one-shot envelopes. Even though this improves upon the flexibility of the two LFOs, I think there should be some useful editing features such as smoothing or maybe the ability to draw a straight line.

Yet another modern twist: The Reverb has a “Shimmer” knob blending the reverberated signal with a copy of itself, transposed up an octave, and a “Regen” knob feeding that transposed signal back into itself for additional octaves. It doesn’t “bloom” like other more sophisticated shimmer effects such as Vallhalla Shimmer, but it’s a pleasant-sounding shimmer, although somewhat shrill on occasion. The Chorus and Delay effects are also quite useful, even though I’d prefer a dual delay for wider echoes.

Another useful feature is “Dual Mode,” which allows you to “stack” two separate patch settings into Parts A and B to play two voices at once and design layered sounds. “Split Mode” is similar, but instead of stacking the two voices, it will assign “Part A” and “Part B” to the keyboard’s lower and higher regions. You can also copy and paste one part to another and save a lot of time programming sounds with very similar settings in both parts without having to go back and forth between them over and over.

As was the case in The Legend, there are hundreds of excellent factory patches from my personal hero Kevin Schroeder, among other enormously talented sound designers: Alex Butcher, Richard Hoffmann, Sascha Meola, Mark Holt, W.R. Bones, Ingo Weidner, Marc Hoppe (Teksonik), Ghostwave and Daniel Thiel (eXode). I was especially impressed by Kevin Schroeder’s cinematic “Textures,” some of which are so modern that you no longer see Obsession as “just another vintage emulation” but something capable of contemporary sound design as well.

Obsession stands out in a rash of OB-Xa clones intent on becoming its software equivalent because it doesn’t try to be. Instead, it’s solely focused on becoming the quintessential modern polysynth, inspired by the OB-Xa’s spirit but not shackled to its legacy. There’s simply no other softsynth offering this much control over each voice or with this amount of attention to detail that has gone into modeling separate voltages and overheating components. It might not be the most versatile instrument due to its overall design, but it’s a lot more flexible than you might realize and absolutely worth a mere $99 price-tag.

More info: Synapse Audio Obsession ($99)

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Synapse Audio's Obsession synthesizer solely focuses on becoming the quintessential modern polysynth, inspired by the OB-Xa's spirit but not shackled to its legacy.

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About Author

Bryan Lake is a sound designer and a musician. He publishes sound design tutorials and sound libraries on his website Sound Author.


  1. marti garaughty


    I love the demos I’ve heard so far of this OB-Xa emulation… such a rich, analog tone to it !

    • You can use a “Const” source in the Mod Matrix to tune oscillators down. But yeah, it would be nice to be able to tune them down on the front panel. I guess that didn’t gel with the vintage design.

      • That’s not what I mean…I mean the actual 2 OSC + 1 sub OSC like on the OB6 for example…I know it’s supposed to be an OBxa emulation…but why not go further… like U-HE did with Tyrell N6 based on the Juno 60…

  2. I just got information that it was released as a Rack Extension for Reason as well.
    And it actually costs the same as the VST!? Now that Reason can load VSTs who is gonna buy a Rack Extension ?

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