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Waldorf Microwave II

Wavetable Synthesizer By Paul Nagle
Published July 1997

Waldorf have been cooking up something special for the son of their acclaimed synth dynamo, the Microwave. Paul Nagle gets quite a taste for it...

After the remarkable success of their Pulse monosynth, German company Waldorf have returned to their first love: wavetable‑based digital synthesizers. The Microwave II continues in the Microwave tradition, replacing the famed analogue filter with an all‑digital counterpart and improving and changing many other features. It's great to play a new instrument not devised out of a desire to jump on a bandwagon or to follow fashion but with the simple aim of perfecting an already classic design.

Physical Things First

Two rack spaces high and only 220mm deep, the Microwave II is sleek and distinctive.The front panel has five edit‑selection switches, a play/shift switch, a power switch, seven bright LEDs, and four continuous knobs which are used to perform all edit operations. It features the familiar large red Microwave knob which, depending on the current mode, is used to select sounds or to scroll through edit pages. The knob is positioned in the centre of an outward spread of ripples used to delineate the programming matrix (does that make sense?). One obvious improvement is in the form of the 2‑line x 40‑character LCD. This isn't as large as some, but does a great job of showing what you need to know. At the rear of the instrument are the obligatory MIDI In, Out and Thru, plus assignable twin stereo outputs and the external power connector.

In Use

Power up and you enter Sound mode, from which you can access 256 patches divided into banks A and B. Patch name, mode (Sound or Multi) and the main volume level are shown, and pressing the Play switch brings up the value of four patch‑programmable parameters to be tweaked during performance. You might choose Cutoff Frequency, Resonance, Filter Envelope Amount and Wavetable selection in one patch, and parameters relevant to the arpeggiator in another. In this mode, the knobs do not send MIDI control changes, presumably because most of the available controllers are already directly allocated to specific Microwave parameters. Don't worry, though, as MIDI controllers are sent during patch edits — almost 80 in total — chosen where direct control would be most useful. The remaining parameters are controlled via SysEx so you can easily record an entire editing session into your sequencer.


Once you've sniffed through the factory sounds (see 'Sounds' box), it's time to enter the wonderful world of sound creation. Pressing one of the edit buttons lights its corresponding LED and gives you access to a series of pages. These are helpfully labelled in the top right‑hand corner by a 'title' which times out after a user‑definable period. Each edit screen has up to four tweakable parameters and when you've altered any, a small 'e' appears after the patch name in the Play screen. You can store your changes, compare them with the untweaked version, or even recall the original without storing — but be careful with this last function: if you recall the patch by mistake, your edits are gone forever. Like the old Microwave, the Mark II has up to eight edit buffers to maintain tweaked versions of your patches.

Waldorf have done a good job with their four continuous knobs, avoiding the sudden leaps that usually happen when knob position doesn't match the parameter value. You scroll through the pages using the Big Red Knob, then use the control knobs directly under the LCD to increment or decrement the displayed value. I am pleased to report that these feel quite heavy but respond positively to a fast turn, taking you to the extremes of any scale; a slow turn is accurate enough for single increments. It's a great pleasure not to have to flick a small cursor around the screen to edit each value.

Ride The Wave

If you look back at the last review of the original Microwave (August 1995's Sound On Sound), you'll get an idea of how this unique synthesis engine works. Suffice it to say here that each oscillator draws its waves from one of 128 wavetables; that's 64 factory, 32 user (created by computer software) and 32 currently 'reserved'. The position in a wavetable can either be static or swept by a variety of modulators for some dramatic harmonic effects. At the end of each table are the traditional sawtooth, square and triangle waves — so you can get pretty near to most analogue sounds too. If you wish, wavetable modulation can be restricted to avoid accidental selection of these three waveforms, preventing an unwanted jump from otherwise related waves. A phase parameter for each wave allows you to home in on individual start samples; if you leave it set to 'free', a new random phase value is set for each note.

The two‑oscillator design of the Microwave II has many of the classic features beloved by synth programmers. Using oscillator sync, those rich harmonic sweeps and searing leads and basses become a reality. The ring modulator takes the output from both oscillators and produces a signal containing both the sum and the difference of the frequencies — useful for clangorous bells, gongs and so on. There's a noise generator for sea, wind and percussive effects too.

The outputs from oscillators, ring mod and noise are all blended in a mixer stage. Also here is Aliasing, described in the manual thus: "a digital artifact that is audible as soon as a wave has harmonics higher than half the sampling frequency. Usually, aliasing is reduced to a minimum by some magical mathematics, but here you can override this and listen to aliasing distortion just like on [sic] the dawn of the first digital musical instruments like the PPG Wave or the old Microwave". Another new feature, Time Quantisation, allows you to undo some of the clean‑up computations done by the instrument, adding extra 'fizziness', especially at the lower end. It overrides the new super‑smooth wave interpolation algorithm, adding some traditional Waldorf harshness. Finally, Clipping selects the type of distortion that is applied when the sum on all mixer levels exceeds 128. Options to choose from are 'saturate', which effectively limits the signal to the maximum level and sounds rather like analogue distortion, and 'overflow', which has a harder, more digital effect. The Microwave II's richness is derived from the raw sound‑making engine and not from some mega effects unit. In fact, there are no effects as such, apart from a quite respectable 'Juno‑style' chorus/ensemble, which is a simple 'on' or 'off' affair.


You can set each patch to be polyphonic or monophonic and use Assign mode to bring forth gut‑wrenching power. Three modes are available: Normal, in which every note played uses one of the Microwave II's 10 voices; Dual, in which each note uses two voices; and Unisono, in which all voices are used, divided by the number of notes played. If you play just one note, you get a massive 10 stacked voices, complete with variable detune between them. Unisono with OTT detune turns just about any patch into a rampaging monster, and I had to resist the temptation to use this trick in everything I created. Other performance modes include glissando and portamento, with linear or exponential response available.


The 'classic' Microwave was a fascinating hybrid combining analogue filtering with a digital wave generator. Its owners, offered another machine, will always ask first: what's the filter like? Can Waldorf really make an all‑digital filter that sounds as good? To my ears, they've largely succeeded. I might have guessed that this was a digital filter by the very slight harshness that sneaks in as you hit maximum resonance — but then again, I might not. It's reassuringly smooth and responsive, but perhaps most impressive is the way it self‑oscillates even with no driving signal from the oscillators present.

In fact there are actually now two filters in series, the first being more versatile with (currently) six settings: 24dB Low Pass, 24dB Band Pass, 12dB Low Pass, 12dB Band Pass, 12dB High Pass and SinX>12L — this last being particularly ballsy and a main component of many of the MWII's most powerful bass patches. I asked the Waldorf team for a technical explanation, and they say that it's a signal shaper with a sine function; the input signal is included in a sine function and its output is used for the 12db filter, so it's simply a kind of saturation which produces nice side‑effects. Anyway, it's rapidly becoming my favourite filter of the lot. The second filter is much more simple: a 6dB slope and either Low or High Pass mode with no resonance setting. If you wish to disable it, simply set the cutoff to fully open.

Having these new filters to choose from permits more delicate sound sculpting than is typically associated with a Microwave — high‑ and band‑pass sweeps cut through beautifully. Now the entire synth is DSP‑based, there's no reason that future developments can't include morphing filters or other, as yet undiscovered, delights.


No synth would be complete without some form of cyclic modulation. The Microwave II has two LFOs with all the expected sine, sawtooth, square, and sample & hold waveforms that we hold dear, plus some additional parameters too. Symmetry adjusts the relationship between the rising and falling edge of the waveform; its values can be positive or negative, so you can continuously vary the modulation shape rather as you can on the Korg MS synths; because a little unpredictability is always useful, a Humanise function adds a random variation to LFO speed. I'd like to have seen these as destinations in the modulation matrix so that you could, for example, modify the LFO waveform or its randomness by velocity. The second LFO is identical except for an additional parameter, Phase, which enables its frequency to be locked to the frequency of LFO1. The Phase offset is an amount in degrees. Both LFOs can be sync'ed to MIDI clock and, like other Waldorf synths, the MWII lets you generate a new Sample & Hold value for each incoming note by specifying a rate of 0. If by any chance this isn't enough control for you, more complex modulation sources can be created using one of the envelopes.


The Microwave II has four envelopes. Three of these are logically connected to specific destinations, but all of them can be overridden. The filter and amplifier envelopes are of the familiar (and most intuitive) ADSR variety; the Wave envelope has eight different times and levels with programmable key‑on and key‑off loops. Finally, the Free envelope has three times and levels plus release time and level.

Using the modulation matrix (see box), any envelope can be assigned to any destination. You can do unusual tricks such as modulating the Wave envelope times (or levels, or both) with the Free envelope while simultaneously using another control source to modulate aspects of the Free envelope itself.


Arpeggiators are very much back in demand again, and the Microwave's is a great deal of fun. Similar to that of the Pulse, it has 16 factory patterns in addition to the usual up, down, alternate, and random sort modes. Notes may be triggered as played, reversed, in note order or in reverse note order, over a range of up to 10 octaves. In an early draft of this review I wrote "some form of programmable pattern would have been nice" but after I upgraded the operating system, which I did not once but twice during the review period (see 'Upgrading' box), this facility magically appeared! So now you can create a user pattern of up to 16 steps and, better still, you can do it in each patch — marvellous. Arpeggio velocity is taken from either the root note or the last note played, this latter being great for emphasising acid blips if you hold a chord and just repeat a single note from it at different strengths.

Multiple (Micro) Orgasms

Multi Mode is where you stack, layer, velocity‑ or key‑split up to eight patches on the same, or multiple, channels. You can route individual sounds to the alternate stereo outputs or use panning to create up to four separate polyphonic outputs. It's handy to be able to override a patch's panning at this stage and thus save the trouble of a search through the modulation matrix to see why your solo is hurtling from left to right.

You get 128 Multis, which is a generous number with a variety of uses — not least to create an absolutely mind‑blowing arpeggiator. Yes folks, in Multi mode you can have up to eight arpeggiating patches, each with its own clock divisions, patterns, sort orders, directions and ranges. This can become an incredible maelstrom of frantic throbbing rhythms and of course you can sync to MIDI clock too — could be the most fun you can have and still discuss it in mixed company...


Lovers of the 'old' Microwave will appreciate the improved user interface, increased polyphony, cleaner sounds, and other new features. Other people, baffled by the original, will probably be equally baffled by the Microwave II, although it's possible that an earful of those huge unison/sync solo patches and that arpeggiator may prove tempting enough to make them take another look.

I'd like to have seen still more enhancements, such as 16‑bit wavetables or — better still — the ability to convert user samples to wavetables via an onboard floppy drive. Maybe we'll see these things in the Microwave III? The characteristic grunginess is very cool, but I feel that the raw sound is still quite similar to that of the first machine; and a synth in this price bracket should, I think, have at least some basic effects included, if only to save you taking a reverb unit to gigs. But the Microwave I is obviously cherished by many users and whether existing owners will trade in their machines to get the new one or keep both, only time will tell. Personally, if I could make a case for 'just one more synth', this would be it. It's different enough to sit comfortably between analogue and sample playback machines, powerful enough to stand out in a mix, and distinctive enough to be a true classic. I was delighted by little touches such as the ease of operating system upgrades and, although I don't think I've done much more than scratch the surface in this review, the potential I've attempted to outline will be mouthwatering for some and daunting for others. If you're not into programming sounds, this synth probably isn't for you — but if you want to cast off the shackles of analogue wannabes and explore a gritty, vibrant digital synth, you simply must test‑drive the Microwave II.

New Features At A Glance

  • 10‑note polyphony
  • Oscillator sync
  • Ring modulation
  • New filter types (the filter is now digital, not analogue)
  • No card slot.
  • Operating System can be upgraded by SysEx commands
  • Arpeggiator
  • 256 patches, 128 multis
  • Improved envelope speeds
  • External PSU
  • Improved display and access
  • Performance knobs
  • MIDI controllers for the majority of parameters
  • Ensemble/chorus
  • Twin stereo outputs

Sounds from the original Microwave can be converted (although some patches will sound different because of architectural changes).


Open up most modern synths and you'll meet a computer stuffed full of complex software. If you've ever had to send one back for an upgrade or a fix, you'll know how frustrating that can be. Waldorf's solution (seen previously on devices such as Roland's VS880) is to provide operating system updates in the form of MIDI files. You play the file to the synth, it responds with 'Receiving System Update...' then 'Updating System...' and, hey presto, you're upgraded! Now that's what I call impressive — let's hope everyone else follows suit.

Updates are available at www.waldorf‑ along with notes on what has been added or fixed; if you don't have internet access, the file is available from your dealer.

Modulation Mayhem

Waldorf synthesizers are well known for their impressive modulation matrices, but with the Microwave II Waldorf have really gone to town. Sixteen modulation routings can be set up, four of which require you to have at least 'O' level maths to understand them. I've reproduced the matrix here to whet your appetite for the kinds of Micro Meals you can serve up:


LFO1, LFO2, Filter Envelope, Amp Envelope, Wave Envelope, Free Envelope, Keytrack (MIDI Note number), Keyfollow (as Keytrack but plus pitch‑bend and glide), Velocity, Release Velocity, Pressure, Poly Pressure, Pitch Bend, Mod Wheel, Sustain, Foot Controller (CC 4), Breath Control (CC2), Control W, X, Y and Z (4 assignable controllers), Control Delay, Modify 1, 2, 3 and 4 (more about these later), MIDI Clock, Minimum, Maximum (these last two being constant values).


Pitch, Osc1 Pitch, Osc 2 Pitch, Wave 1 start position, Wave 2 start position, Wave 1 mix level, Wave 2 mix level, Ring Mod level, Noise level, Filter 1 Cutoff Freq, Filter 1 Resonance, Filter 2 Cutoff, Master volume, Pan, Filter Envelope Attack, FE Decay, FE Sustain, FE Release, Amplifier envelope Attack, AE Decay, AE Sustain AE Release, Wave Envelope times, Wave Envelope levels, Free Envelope times, Free Envelope levels, LFO1 rate, LFO1 level, LFO2 rate, LFO2 level, Amount of modulation assignments 1‑4.

A note on modifiers: up to four modifier units can be set. These consist of two modulation sources and a mathematical relationship between them. The functions available are: Addition, Subtraction, Multiplication, Division, XOr, Or, And, Sample & Hold, Ramp, Switch, Absolute value, Minimum Value, Maximum Value, Triggered Ramp, Low‑pass filter, Differential Function. If this all seems a little heavy, that's because it is!

It's a little beyond the scope of this review to examine each of these in all their glory, but all kinds of interactions between modulation sources can be used creatively, from the simple addition of control signals to the building of a modulation signal governed by the mathematical criteria listed.


During the obligatory tour, some of the patches that particularly impressed me were: A01 Unisono, a monster lead patch using oscillator sync and unison mode; A25 Deep Spaces, a strange ambient backdrop; A28 Ocean, another magical pad; A48 Mello Choir, an eerie choral interpretation; and A78 Why TB?, which you'd swear was one of those new‑fangled computers pretending to be an analogue synth — great use of the mod wheel mapped to filter cutoff. A88 Sub Woof shows off a speaker‑shaking bass end (a result of cleaner circuitry and new filters, apparently); A18 Big Balls is, as it implies, powerful; and B15 18dB Acid is a squelchy synth. There's also the usual collection of weirdies, but many serve as starting points for patches of your own, and I suppose it would hardly be a Waldorf synth without some unfathomable noises...

The preliminary manual is a slender tome of 60 or so pages with tantalisingly scant detail on the meat of the programming. A full manual is promised as an incentive for owners filling out their warranty cards.


  • Unique sound.
  • Superb programming power.
  • Painless upgrades and expandability.
  • Great MIDI implementation.
  • Continues familiar Microwave tradition.


  • No effects.
  • External power supply.


From the first monster unison solo to the last swirly string pad, the Microwave II pulses with dark power. Rich resonant sweeps, PPG‑like wails, delicate solo voices and strange, shifting digital soundscapes are all here. Potential buyers of a Microwave II won't be looking for a GM logo or realistic piano samples; instead they will be explorers in synthesis determined to uncover sounds that can't be produced by other means.