Make Noise need almost no introduction. Among the prime movers in the Eurorack explosion, former Moog employee Tony Rolando and his crew broke on to the scene with a distinctive street‑art‑meets‑hieroglyphics aesthetic and a certifiably maverick attitude towards circuit building.
On first glance you might think their new flagship standalone oscillator, the XPO, is simply a sequel to the much lauded DPO, and although it does incorporate elements from that design, the abbreviations indicate otherwise. While the DPO is a Dual Primary Oscillator, the XPO is a Stereo Prismatic Oscillator, departing from the DPO’s architecture in several key areas. Rolando, interestingly, did purportedly refer on occasion to the DPO as a Dual Prismatic Oscillator, indicating that the journey to the XPO has been a long one. The genesis point of the XPO, according to Rolando, can actually be traced more accurately to the voice panning of the Oberheim OB‑8. “So simple, so effective,” he wrote on the Make Noise website. “Then it occurred to me, why couldn’t PWM [pulse‑width modulation] be stereo? It would be very effective at creating a stereo image since the amplitude of both left and right would be almost identical, while still offering dramatic stereo timbral shifts. I thought to myself, surely somebody has done stereo PWM already. I needed to research this idea. So I wrote about it in the notepad I keep on the nightstand and I eventually fell back asleep.”
In his extensive research following that dreamlike revelation, Rolando came to realise there was in fact a dearth of stereo applications of PWM, and I suppose the rest is history. A monophonic all‑analogue oscillator based on a triangle wave core, the XPO offers three sets of stereo outputs, five mono outputs (that’s a whopping 11 separate outputs), two summed volt‑per‑octave inputs and many, many modulation possibilities. There are elements of Make Noise’s aforementioned DPO and QPAS filter here, not to mention plenty of the trans‑American synthesis school‑mixing characteristics that (literally) made the name of the semi‑modular 0‑Coast. The XPO is a beastly thing with legion tricks up its sleeve, that I daresay I would not exhaust with weeks of experimentation.
In a world where spatial audio is marketing itself as the sound of the inevitable march of progression, it’s easy to forget that there is still infinite uncharted territory and abundant creative potential when it comes to our old friends, L and R. Make Noise, it would appear, are invested deeply in this idea. There’s the now‑iconic, two‑channel Maths function generator, the aforementioned DPO dual VCO, the stereo Mimeophon ‘audio repeater’ and of course the QPAS stereo filter, with which the XPO is alleged to pair famously. Make no mistake: stereo is as lush a sonic territory to explore as it has ever been, and then some.
As mentioned, the XPO has an astonishing 11 possible outputs. These consist of a top row of singular sine, triangle, saw, spike and sub‑octave outputs, alongside stereo pairs of PWM square‑wave outputs, sine‑triangle variable ‘Vari‑Timbre’ outputs and sine‑based wavefolder outputs. Of these, we might chalk the triangle, saw and square‑wave outputs up as East Coast circuits and the spike, sub, Vari‑Timbre and wavefolder outputs as West Coast (perhaps even along with the FM‑friendly sine wave). More specifically, the spike wave nods to the Buchla Music Easel synth, while the Vari‑Timbre and wavefolder pay homage to the Buchla 158 and 258, and the 259, respectively. Remember all that about love letters? This is what I mean, and isn’t it fantastic?
In any case, immediately upon powering up my XPO I was able to populate an entire mixer with glorious, wide washes of oscillations, processing and filtering any combination of them through various other modules to create a truly humongous, multifaceted drone without so much as patching anything into the module at all. While the XPO’s mono outputs can take any comparable Eurorack oscillator to task, here they are rendered relatively utility, since the XPO’s focus is undoubtedly on its three sets of stereo outputs. Two Modulate knobs shape the output of the left and right sides independently of one another, eliciting a different response from each stereo set: they modulate the PWM square‑wave outputs’ pulse width (in case that wasn’t clear already), they graduate the Vari‑Timbre outputs from sine to saw, and on the wavefolder they, well, fold the wave. For the latter two sets there’s an additional control, Center, which ostensibly sets the core wave shape that ‘feeds’ each of these two circuits when their respective Modulate controls are turned up sufficiently.
It doesn’t stop there with the XPO’s modulation potential. Two FM inputs — one linear and one exponential — offer more sound sculpting and self‑patching potential. This also helps to explain why there are so many different outputs on the XPO: it’s a veritable powerhouse of harmonics in almost every way you can think of. The linear FM is normalled to the XPO’s sub‑octave oscillator, which is a nice touch. This means that even when unpatched, the linear FM attenuator can achieve anything from subtle growl and quasi‑distortion to tonally unhinged chaos. There is also a rather unique‑sounding oscillator sync input that doesn’t quite adhere to the laws of soft or hard sync; instead it creates more of a ‘rippling’ effect (to use the apt term put forth in the XPO’s manual) that once again endows the XPO’s sonic signature with fascinating, at times guttural timbres.
Two volt‑per‑octave inputs complete the XPO panel, but don’t be fooled into thinking this indicates duophony. These might look like they promise to control each side independently, something not helped by their placement on the panel, but in reality are identical if used individually and become summed when used together. This isn’t so much a criticism of functionality as it is just a bit of a red herring, since duophony would in many ways undermine the whole point of the XPO: which is to explode its waveforms into as many harmonic splinters as possible while retaining the integrity of that big, brash, gloriously bold singularity that is a monophonic analogue voltage‑controlled oscillator.
It may feel like spatial audio is the talk of the town in 2023, but stereo’s horizon is still expanding and the XPO ably demonstrates that. It’s wide and lush, replete with complexity and texture, and a worthy addition to the Make Noise family. Marvellous.