The new XPO or Stereo [Xtereo?] Prismatic Oscillator from Make Noise is an 18hp stereo oscillator that follows in the footsteps of other stereo modules like the QPAS, XPAN, and Mimeophon that have been released by Make Noise over the past couple of years.
While the XPO’s soul is certainly stereo it consists of only a single oscillator core that can be manipulated separately in the right and left channels for massive swirling spatial movement. Instead of different oscillators for each channel the XPO instead utilizes different waveshaping and blending techniques to create its stereo movement.
The XPO has a grand total of 11 audio outputs. Five mono outs for the classics–sine, triangle, and sawtooth, as well as a “spike” waveform, and a sub waveform which isn’t just a simple square wave but more like a staircase wave. In addition to these, there are three stereo output pairs; a pair of pulse waves, what Make Noise calls its Vari-timbre outs [a continuously modulatable blending of sine, saw, and triangle waves], and a pair of stereo wavefolder outputs.
Inputs and controls consist of knobs for both coarse and fine tuning, an exponential FM input with attenuverter, a linear FM input which also has CV control over the amount and index [conveniently, the sub is normalled to this input], a sync input, two v/oct inputs, and identical modulation inputs with attenuverters and manual control for both the left and right channels. The channel modulation controls will look familiar to QPAS owners as the set up is similar on the XPO with a left channel modulation input normalled to a right. Lastly there is a knob for control over the module’s “center” parameter as well as an associated control input jack.
The mono waveforms on the XPO offer a nice variety of great sounding, meaty, analog shapes. The more novel inclusion of the spike wave—which sounds like a thin pulse wave or a really high-passed signal—and the harmonically rich sub waveform add a welcome variety to the more bread-and-butter shapes. These mono outs with the linear FM controls and the normalled sub input is enough to keep you patching happily for a long time to come, not to mention having them available for other uses within a patch, but the real stars of the show on XPO are the three pairs of stereo outs.
The PWM outputs are independently variable-width pulse waves and provide a rich and phase-y swarming churn of buzzy goodness. The modulate-L and modulate-R control each channel’s wave separately and because of the clever normalization you can get great movement happening with just a single modulation input. The center does not affect the PWM outputs.
The Vari-timbre outputs are controlled by a combination of the modulate-L, modulate-R, and center controls. Center blends between sine and saw between each channel, while the modulate controls dial up a triangle wave into the mix. Vari-timbre’s various timbres are easy to get lost in, following the paths of different textures and variations introduced with each subtle parameter tweak.
The wavefolder outputs are also heavily affected by the center, modulate-L and modulate-R controls. Instead of straight ahead wave folding however, the modulate-L and modulate-R actually move the signal from silence when fully counterclockwise, increasing the sine-ish wave in amplitude and eventually folding as the modulate controls are moved clockwise. Center blends in a triangle wave and relatedly affects the point at which folding begins. It adds a thinly aggressive timbre and buzzy-ness to the sound.
The XPO has only a single oscillator core and the two v/oct inputs aren’t intended for duophonic output but they are super useful for creating interesting sequence transpositions and interactions and ring mod-like scaled audio rate modulation.
The amount of stereo signal goodness available in the XPO can lead to some fantastically complex and evolving timbres with surprisingly little effort, and the clever normalization of the sub octave into the linear FM circuit and the stereo modulation controls make for effortless spatial dynamics with minimal external input. Of course, the more you put in the more you tend to get out, and the XPO shines for sonic exploration and stereo manipulation.
With their latest release Make Noise proves once again that the whole is greater than the sum of its parts and the XPO beckons one to explore that mysterious interplay between intention and exploration that so many of us get into Eurorack in the first place for.
 
18 HP +12v 145mA -12v 135mA
Price: $399

makenoisemusic.com