Modcan FMVDO Demo

The Modcan FMVDO is a one-stop FM machine. It offers all you need for stable 2-Operator FM: a carrier, phase-locked modulator, an index VCA and more, all in 12HP. Could this be the gig-able solution I've been looking for?


Buy the album for €1 or more to access the full files (14 tracks, 19 mins), including comparisons with the WMD PDO.

The FMVDO first caught my attention four years ago, so I was very keen to try out the new Euro version. It offers better fidelity than the Hertz Donut and PDO and its features seem more focussed than the Cyclebox. As you can hear from the recordings, it sounds wonderful. I was expecting the glassy and wooden tones, but was surprised at some of the abrasive noises it's also capable of. So, problem solved? Well, not exactly …

Although it's more hi-fi, the FMVDO is also prone to mild aliasing. More importantly, the comparison with the PDO shows that its maximum modulation depth is not as deep. At higher indices, the PDO's digital wave-shaper distorts, but this can be tamed whilst still yielding brighter tones. Because the FMVDO's FM takes place internally, you can't increase the modulation above a certain point.

The all-in-one nature of the FMVDO raised a few other questions. I'm very particular about my envelope and VCA pairings. If you don't like the internal index-VCA's response, you're stuck. The inclusion of amplitude modulation is a nice feature, but I found this could be a little dirty, depending on the frequency. When active, the internal quantizer ensures that tuning ratios are maintained. It's fantastic to see this included, but I did get the impression that it wasn't always stable.

The ability to select waveforms via CV is something I wish the PDO had. On the FMVDO, this can result in radical changes in timbre. The waveforms are well-chosen. Some only reveal their true nature in LFO mode. The secondary output is fixed at 90 degrees. It can be used for stereo effects or quadrature modulation duties. Unlike the PDO, which is based on phase modulation, auto-modulation with this output won't result in wave-shaping. But as you can hear, it does create some wonderfully unpredictable results.

The Modcan FMVDO is well built, feature-packed and an excellent source of FM sounds. Sonically, it's 'superior' to the PDO, but I found myself preferring the more robust nature of the WMD. Part of this might be the difference between FM & Phase Modulation. PM is more forgiving of ratio inaccuracies than FM. That's possibly one reason why the FMVDO keeps everything 'in the box'. Make sure you try it out to see whether that suits the way you patch.

Thanks to Schneidersbuero for the loan of the module.

WMD PDO Demo

Audio examples and review of the WMD Phase Displacement Oscillator. A sequel to this post.

The WMD PDO is a timbral oscillator with a twist. Three of its outputs can be discretely shifted in phase relative to the first. It can be used as a quadrature LFO, but the real fun starts when modulated at audio rates. This yields results similar to linear FM, but as the PDO’s creator William Mathewson says in one of his promo videos, phase modulation “gives you more”. Here it is in action:


The sounds in the multi-tracked demo track were generated by modulating the PDO either by itself, for wave-shaping, or an external VCO for PM effects. Buy the EP to access the full set of unprocessed demos (10 recordings, 30 mins duration).

As you can hear, the PDO is capable of a wide variety tones: deep acid basses, bright bells, wooden klonks, scraping steel strings, rasping super-saw/ PWM sounds, even digital noise. As with the Zeroscillator, panning two phase shifted outputs hard left and right can result in stunning stereo effects.

I found I could push the PM index harder and get brighter sounds than with either the analogue ZO or digital Hertz Donut. Like thru-zero linear FM, when the PDO is modulated with a bi-polar signal, its sign, or direction, changes. However, modulating the phase rather than the frequency results in less pitching artifacts.

That's not to say the PDO is artifact-free. At slower modulation rates I thought I could see/ hear the PDO 're-calculating' the phase offset, resulting in a mild siren effect. I asked William about this and he explained that this was the nature of phase modulation; what I was hearing was similar to the Doppler effect where moving the phase forward increases the frequency. At higher audio rates this was not apparent, but it might have an effect when using the PDO as an LFO. The digital wave-shaper means aliasing is apparent and the sound can break up at extreme frequencies or when FM-ed hard. However, I took this to be part of the PDO's character and, as you can hear in the demo track, it means you have another set of timbres to play with. I thought the saws and pulses were not as beefy as an analogue VCO and that it was a shame that one can't affect pulse width and phase simultaneously for 'shonky beats'. However this can be addressed by routing a shifted output to the reset input via a clock divider.

These are minor points given the wealth of sounds and possibilities packed into the PDO's 10HP. In fact, that would be my biggest criticism: it's pretty cramped! I'm sure I'm not the only one who'd gladly devote more rack space to a larger PDO, possibly with an onboard sine modulator and index VCA. As it is, the list of modules the PDO could replace in my system is shocking - it's perfect for a live set-up or desert island suitcase.

There is one last thing to consider: at almost €400 the PDO is in the same price category as the SynthTech E350 and Cylonix Cyclebox, which both offer increased fidelity. Whether they offer the same depth of phase modulation and character is something I look forward to testing in a future post.

Thanks to William for taking the time to answer my questions and for a great module!