Like the Minimoog, Oberheim‘s OB-X, OB-Xa and OB-8 are among those analog synthesizers that have the most software replicas. It’s no wonder since these three polyphonic synthesizers from the early eighties wrote music history with their warm and voluminous sound and still enjoying great popularity today.
Purist with Add-ons
For Obsession (checkout Obsession in the Thomann shop), Synapse Audio used the OB-Xa as their model, using Curtis chips for the oscillators and the filter. The layout with two oscillators, noise generator, resonant filter, two LFOs and two envelopes is well known from its hardware counterpart. In both oscillators, you can select sawtooth, square, a mix of both, and triangle waveforms. In Sync mode, you can create wonderfully cutting sounds. Fortunately, there is also a cross modulation option onboard, which (in hardware form) was reserved for the OB-X. It sounds very convincing, as does the pulse width modulation. The plug-in‘s filter allows you to switch between a 2- and 4-pole model, just like the OB-Xa. An excellent addition is the bandpass mode.
Double the Fun!
Like the OB-Xa, the emulation allows you to create layers and splits from two sounds. The plug-in can be played with either 8- or 16-note polyphony. By disabling all the voices except one, monophonic is also possible…and a legato option is already in the works. Despite its rather simplistic and straightforward synthesis architecture, the OB-Xa is a wonderfully multi-faceted instrument; and Obsession is in no way inferior to it: Powerful basses and gripping lead sounds are great – as are the characteristically lush brass and pad sounds. Even extremely musical sync, effect sounds, fat unison and split sounds are all an easy exercise. Awesome!
Emulation in Detail
The variations between the individual voices make the sound of the OB-Xa very lively and full of character. With Obsession, you can set a variety of synthesis parameters for each voice, like the filter frequency and the envelopes. Using this method, you can create lively sequences with up to 16 steps. You can even vary the modulation intensity per voice. These additional plug-in features impressively expand the sound potential without the synth distancing itself too much from the concept of its vintage counterpart. Above all, we would have liked an arpeggiator – especially for split sounds; but in step mode, arpeggio-like sequences can be achieved. You can also create microtonal note sequences that are just not possible with classic arpeggiators.
Like the Minimoog emulation “The Legend” (also by Synapse Audio), more advanced settings can be found on the „back“ of Obsession: Here you’ll find, among other things, saturation level, a limiter and a modulation matrix with six slots. Various MIDI controllers are available as modulation sources. In addition to all the synthesis parameters, the effect settings can also be controlled. Another special feature is the aforementioned Step Mode in LFO 1 and 2 where you can draw in up to 128-step sequences each - perfect for tempo-synchronous rhythmic modulation! The Organic control lets you adjust the intensity of the variations of each voice to recreate the behavior of vintage synths. There’s a dedicated effects section with delay, reverb (with shimmer option) and chorus and they greatly enhance the sound.