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Waldorf Pulse 2

Analogue Synthesizer
Published February 2014
By Paul Nagle

Waldorf have followed up their '90s blockbuster with a sequel — the Pulse 2.

Casting my mind back to 1996, I can clearly remember the impact Waldorf's Pulse made, emerging as it did from the same stable as the mighty Wave and Microwave synths. Physically demure yet sonically bloated, the Pulse and later Pulse Plus were monophonic analogue synthesizers with three oscillators, a morbidly obese low-pass filter and MIDI control over every last detail.

With continuing advances in technology, who would have predicted there'd be more small analogues now than then? But with many companies rediscovering the sounds that inspired us once upon a time, Waldorf have charged the defibrillators to kickstart a Pulse for the 21st century. It took them longer than expected (the Pulse 2 was announced in early 2012) so does this newcomer possess sufficient 'wow' to make hearts flutter again? Let's put aside the weak medical analogies and take a look...

Leaving The Rack

Adopting its form factor not from the original 2U rack Pulse but from the more recent Blofeld, the Pulse 2 is a beautifully engineered desktop synth in cold, curved metal. The black and green design is confidently striking, the six encoders luxurious and weighty, with a natural-feeling software acceleration when required. In conjunction with a typical Waldorf programming matrix, they're sufficient to edit every parameter.

If you count the LEDs you'll see this matrix has nine rows and that there are therefore 54 individual voice elements to tweak. With familiarity, you should be able to make edits almost as fast as you could on a larger, knob-strewn panel because, at just 304 x 132 x 54 mm, the Pulse 2 is surprisingly uncramped. The display is bright and clear but — perversely — most of its pixels are dedicated to reporting the current patch number,with the patch's name and class shown underneath in much smaller text. With 500 patches in total, accessed by just a selection dial and two buttons, you'll be glad of the category-based search option.

The six buttons that take care of row selection double up as access points for global options, utilities, the modulation matrix and patch storage. Annoyingly, during the save process, there's no visibility of the destination you're about to overwrite. So if you've done a spot of tweaking and require a permanent home for your work, you must find a new location while being ultra-careful not to touch any encoders or send any stray MIDI CCs. If you do you'll lose all your edits. Having found a suitable slot, you return to the edited patch and perform the save operation. Let's hope Waldorf pick a friendlier way to achieve this in future!

It's nice to have the choice of driving the Pulse 2 either from its five-pin MIDI input or from its class-compliant USB MIDI interface, but perhaps as a sign of cost-cutting, there's no dedicated hardware Thru. In partial compensation, the MIDI output can be configured to act as a combined Out and Thru. This becomes relevant when you realise every parameter adjustment, plus the notes generated by the arpeggiator, can be transmitted.

In order to process the audio of your choice through Waldorf's multimode filter, there's a single input jack. Interestingly, the Pulse 2 matches the earlier models in having stereo outputs even though, as before, the voice architecture is resolutely mono. If you can spare two mixer channels, there's a fair bit of mileage in tossing a single voice around the stereo spectrum, especially at the speeds attainable by these LFOs.

If there's one area in which the newcomer lags behind the Pulse Plus it's voltage, present here in output form only. The CV and Gate outputs provide an easy mechanism for controlling an analogue synth and, although just a single CV feels a bit stingy, it can be repurposed for several types of voltage delivery.

All audio and CV connections are on regular quarter-inch jacks, which you'll appreciate if you've ever run round like a headless chicken five minutes before a gig searching for a mini-jack adapter. Finally, a small 12V external power supply is provided to transform the Pulse 2 from a rather elegant paperweight into a living, breathing analogue synthesizer (with digital bits).

The Oscillators

To get a taste of this pocket-sized Pulse, I took a quick stroll through the factory sounds; at least I intended it to be quick. Instead, with 400 of the 500 patch memories already filled, an afternoon slipped by as I sampled the various arpeggios, basses, leads, pads and sound effects. It's a wide-ranging collection crammed with sounds I've never heard from a Pulse before — and a valuable source of programming ideas to boot.

You may have noticed I slipped in 'Pad' just now as a category and it's true that with three oscillators — digitally controlled analogue oscillators — you can create triads to play from single notes. However, the Pulse 2 also borrows an idea from Waldorf's Rocket synth and offers up to eight note polyphony.

The Pulse 2's back panel features, from left to right, a headphone port, stereo outputs, an external input, CV and Gate outputs (all on quarter-inch jack sockets), MIDI In and Out, a USB port and an input for the external 12V power supply.

How is this possible? Well, according to Waldorf, there are eight analogue oscillators for square-wave related shenanigans, but only three analogue-controlled saw/tri waveshapers (with individual mixer VCAs). These components are juggled around to produce different operating modes, but with several enhancements over the Rocket's implementation. It must be stressed that, post-oscillator, the voice architecture is strictly monophonic; ie. there's a single filter and VCA with an envelope to shape each. Therefore, the accurate description is 'paraphonic' and there are two 'para' modes assignable to DCO 1, plus two stacked unison modes thrown in for good measure.

When you select Para8 mode, up to eight incoming notes are given a pulse oscillator each, while DCOs 2 and 3 are disabled. If I can draw your attention for a moment to the top row of the programming matrix, you'll see the fifth encoder is 'Keytrack'. Ordinarily, this determines whether incoming notes track oscillator pitch, but in either of the Para modes, it becomes a simple fade envelope for the pulse oscillators. Para4 differs in that only four notes are assigned, but they're doubled up; the second layer's interval, detune and fade envelope are dialled in with the controls of oscillator 2. A similar stacking of pulse waveforms occurs in the unison modes, of which there are mono and poly versions. In mono unison all eight oscillators are stacked on a single note, while the poly version divides them freely amongst the notes played. If you enjoy a high-fat diet, this is seriously addictive, and though paraphony is unlikely to be the only reason to get a Pulse 2, it's no frippery.

The DCOs are equipped with typical analogue waveforms, but probably the most welcomeadvance from the original Pulse is a more subtle detune. While not so loose and swimmy as classical oscillator designs, these handle well and feature several innovations for extra spice. Of these, the first oscillator's 'APW' is yet another type of pulse waveform (I'm starting to guess how the synth got its name!). APW, or Alternate Pulse Wave, is a pulse with an added subharmonic pitched an octave down. Select APW and even when you vary the pulse width the subharmonic remains constant. This prevents the usual disappearing act that occurs when the width hits zero.

Oscillator 2 lacks APW but instead offers a rather novel cross-modulated PWM, its source either of the other oscillators. Thanks to the wide and stable tuning (+/- 48 semitones), the ensuing cross-modulation spawns a host of complex waveforms, often with an atonal, near-digital edge.

On first glance, oscillator 3, with its simplified palette of triangle, saw and square waves is the poor relation — so poor it can be kicked out entirely, in favour of an external signal. Or, if you pick 'FB', the oscillator is replaced by a feedback path from the drive output, which, according to my ears, generates a more ringing character in the filter than ordinary resonance. The third oscillator may also be rerouted for exotic duties such as being a modulation source for DCO 2's level, the filter cutoff or VCA drive. In the first of these we're firmly back in atonal, 'ring-modulatorish' territory, while FM is always worthwhile for creating extreme, sometimes formant-like filter tones. The effects on VCA drive are largely dependent on the selected drive curve, about which more anon.

Given its flexible routing and modulation, it's a shame there's no simple on/off switch for oscillator 3's keytracking, as per the other two. Instead, that position in the programming matrix is used for a switch that enables hard sync of oscillator 2. I wasn't madly enthused by the lumpy and grumbling sync and found it most effective when the synced oscillator's pitch sweeps were fairly restrained.

Filter Skelter

Through the late '90s, the Pulse's fast, snappy envelopes and solid 24dB filter made it an ideal choice for bass, but there were times when it was too blunt an instrument. The Pulse 2 has more sculpting power in this respect, courtesy of a multimode filter with a low-pass 24dB mode and 12dB low-, band- and high-pass modes. The characteristics of the filter alter according to the level of the oscillators and the VCA drive curve, while the resonance is always ready to break into self-oscillation with minimal provocation. The low-pass modes are both well up to scratch, with the 12dB version ideal for pads and brighter, more delicate material. Of all the filter's modes, I was least impressed by high-pass, which was functional but somewhat lacking in character.

I should also point out that adjusting filter cutoff was a nicely rounded experience, but some of the other controls were audibly steppy; for example, the filter's envelope amount and key tracking.

The Rest

Two ADSR envelopes are provided, hard-wired to the VCF and VCA, although, like most modulation in the Pulse 2, they can be freely allocated in the mod matrix. For convenience, velocity is a permanent connection that's instantly on hand to drive either (or both) ADSRs. Thanks to a choice of looping options, the envelopes can operate like basic LFOs and they're fitted with sufficient triggering options to cover mono and paraphonic duties (and keep picky reviewers blissfully content).

As on the classic Pulse, there are two LFOs and these have a wide frequency range, from almost stopped up to around 100Hz. The first is the most well endowed, having MIDI synchronisation and extra waveforms, while LFO2 is essentially a triangle wave with the added bonus of a variable onset time. Tucked away on the same row, glide deserves a mention for its rather quirky mode: 'FOFF'. Rather intimidating in its abbreviated form, this represents one of several means of introducing glide by playing legato. In the case of FOFF, the pitch doesn't glide in the direction of new notes but is engaged during the journey back to the held note. It's a simple twist on a familiar theme but after decades of regular gliding I found it a pleasant alternative.

Along the bottom row of the programming matrix are output-related items such as panning (assuming you've connected both outputs), the level of white noise and the VCA response to velocity. Here also you can select a drive curve from a choice of either tube or fuzz. Tube employs asymmetrical distortion to produce a satisfying and versatile overdrive — made even more interesting when its level is modulated in some way. Fuzz is blatant, noisy distortion and I found it to be of less instant value, but even a small amount was enough to make the Pulse 2's presence felt in most of my mixes. There's one last undocumented entry in the drive curve list: FX. Waldorf tell me this relates to a tiny effects board about which, because it's still in development, they're not giving out any details at this stage.

During my testing I noticed patch changes were delivered at an impressive speed and I discovered I could run a single sequence that switched between a bass patch, a high hat and a chord stab, all without the Pulse 2 missing a beat.

The Pulse 2's front panel: light on knobs, heavy on modulation destinations.

Into The Matrix

Just as a Waldorf salad needs mayonnaise, so a Waldorf synthesizer needs a modulation matrix. It's accessed by pressing the lowest of the row buttons in conjunction with 'Mod', after which near-modular connectivity is at your disposal. From a selection of 24 sources and a similar number of destinations, geeks, wizards and sonic explorers have up to eight virtual patch cords to play with. If this weren't enough, several built-in mathematical functions should appeal to anyone with an interest in compound, interacting modulation.

Within minutes, I began constructing an electric koto patch, mainly because I was curious to try setting the speed of a looping envelope with a controller such as the mod wheel. Having started down the plucked string route, with just a few more matrix slots I was able to introduce a dash of filter FM and additional high harmonics by modulating oscillator levels with velocity. It's the sign of a misspent youth that I still get a buzz from fresh modulationconnections, whether this involves having an envelope speed up an LFO or more involved examples such as adding real-time performance smoothing to a sample-and-hold waveform. Smoothing is one of those mathematical functions I mentioned earlier that, along with addition, multiplication and the plucking of one value from several, helps distance the Pulse 2 from its contemporaries.

In the end, the mod matrix doesn't have to be about indulgent, nerdy programming. Even a single matrix slot can be invaluable; say for converting a MIDI-sync'ed LFO into a voltage suitable for use with a modular or semi-modular synth.

Conclusion

The Pulse 2 doesn't offer the tweakability of its current rivals, but what it lacks in knobby acreage it compensates for in programming nuance. Despite the matrix-based access method, the Pulse 2 is no slouch to operate, but it could be even faster if the display gave up its obsession with the patch number and showed every value of the selected row instead. In a similar vein, I don't care that there aren't graphical envelopes or images of waveforms, but I would really like to see the name of the patch I'm about to overwrite during a save operation. At least there are no complaints when it comes to the patch storage capacity, which is five times that of the original Pulse!

Further bonuses include a better-than-average arpeggiator and those CV and Gate outputs, but the Pulse 2's core strength is its eagerness to be pushed far beyond regular monosynth boundaries. Paraphony, unison and those cross-modulated pulse waves trump the original model from every angle, and the filter is more versatile too, especially when roughed up by a splash of tube overdrive. Ultimately, if you appreciate analogue with added bite, the Pulse 2 is an aggressive, lively imp of a synth that can buzz, growl and screech like nothing else in its class.  

Alternatives

Dave Smith's Mopho is a cheaper, less complex alternative that conceals extensive modulation capabilities and a fun sequencer behind its stripped-down interface. Or, for a similar price, you could opt for something larger, knobbier and with a novelty keyboard. Both Korg's MS20 Mini and Novation's Bass Station 2 (to name but two possibilities) offer their own special flavours of cutting edginess. So while it's not easy to pick a clear winner on all counts, one thing's for certain: there's never been a better time to buy a sizzling, brand new analogue synthesizer.

The Arpeggiator

The arpeggiator page is one of only a handful in which the patch number doesn't dominate and one press of the Arp button treats you to a full screen devoted to chord slicing. At the most basic level you pick the direction, speed, range, swing and so on, but if you enable the pattern editor the real fun can begin. Glide and length variations can be introduced for specific steps but, going deeper still, events may be added to modify the behaviour of each step, in patterns of up to 16 steps. Modifications include transposition and the shifting of velocity, plus the conditional playing of steps on odd or even cycles. Usefully, you can audition the patterns of other patches directly from this page, all of which makes for an arpeggiator well worth getting to know.

CV/Gate

The CV and Gate outputs support both Oct/Volt and Hz/Volt standards and it took only a little CV tuning and adjustment to achieve a very reasonable spread of seven octaves from my Roland SH101. Ordinarily, the CV output mirrors the MIDI notes used by the Pulse 2, but (and unlike the Pulse Plus) there's no scope to assign this function to a separate MIDI channel. Nevertheless, there's bags of potential to explore, not least for the control of external oscillators, which you might then introduce to the Pulse 2's signal path for further sonic variety.

Alternate configurations switch the CV output to either a unipolar or bipolar voltage, ripe for exploitation in the mod matrix.

Published February 2014