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Waldorf Microwave XT

Wavetable Synth By Paul Nagle
Published October 1998

Waldorf Microwave XT

The latest addition to Waldorf's Microwave family certainly advertises its presence. Paul Nagle finds out if the future's bright as well as orange.

Boasting possibly the most extravagant colour scheme yet seen on a synthesizer, the Waldorf Microwave XT is no shrinking violet. Brashly elbowing the more demure Microwave II from its 'top Microwave' spot, the XT is the newest, biggest and most orange member of the family ever. Why orange? I can't say, but it certainly stands out in a rack — it positively demands attention! If you are a lover of small black boxes full of piano samples, stop reading now, because you won't like the XT. The mad scientists in Waldorf castle have created a monster — the head of a Microwave II grafted onto the body of a knobby analogue‑style synthesizer.

Wave Hello

The Waldorf Microwave XT is a 10‑note polyphonic digital synth sturdily housed in a large rack/desktop case (if racked it occupies five spaces). As it shares a common operating system with the Microwave II, please read the review from July 1997's Sound On Sound for a reminder of the joys of its wavetable synthesis, digital filters and extensive MIDI control. Since that review, Waldorf have been busy (as is their wont), upgrading and improving the operating system. These enhancements have been provided over the last year free of charge, in the form of simple MIDI files. The improvements include Oscillator FM, a new wavetable — True PWM, an extra 6dB output boost (for the XT only), a patch randomiser (which creates great 'starting points' and strange sound effects), four new filter types and DSP effects. I really should mention the filters which are: Waveshaper (a 12dB low‑pass filter combined with a wave‑shaping filter, the wave selected from the current wavetable), a Parallel Low Pass/Band Pass filter, an FM filter (whose frequency can be modulated by the output of Oscillator 2) and the Sample and Hold filter (which lowers the sampling rate of the signal before routing it through a low‑pass 12dB filter). The DSP effects include Chorus, Flangers 1 and 2, AutoWah (Low Pass and Band Pass), Overdrive, Amplitude Modulation, Delay, Pan Delay and Chorus Delay. These are quite impressive as freebies, but Waldorf must have felt the urge to show off with some new hardware as well, and thus the XT was born.

So what else makes the XT the hottest Microwave yet? Well, its D/A convertors are 20‑bit (as opposed to the Microwave II's 18 bits) but, for now, let's concentrate on what really sets the XT apart from its smaller sibling. We're talking knobs, and not just a few.

A Programmer's Dream

Everyone's rediscovering knobs these days, and Waldorf obviously believe that a more 'hands on' interface will bring their wavetable synthesis to the masses. In fact, the Microwave II was already very easy to program with its simple matrix, alpha dial and 2x40‑character display. Under this display, four continuous knobs were used to make all edits, and could also be freely assigned as 'Play Access' controls in each patch. These features are carried through unchanged to the XT. The addition of 40 more knobs, plus three additional switches and a dedicated volume control is nothing short of luxury, providing direct access to all the Microwave's major features. Only one of the knobs, Main Volume, is of the traditional 'absolute' variety. The rest are continuous, a design which makes tweaking filter, envelopes and so on a real pleasure. There are no more sudden leaps because the knob's real position doesn't match the stored one — the stored value simply increments or decrements smoothly. This is superb for live work, and easily the best solution I've seen since synths first got patch memories. Those knobs which control discrete parameters (oscillator octaves and semitones, filter types, wavetable selection and LFO waveforms) have subtle notches for more accurate editing. As you turn a knob, the new value is temporarily displayed in the top right‑hand part of the screen; if I could suggest any improvement, I'd like to see the original stored value appear next to it too.

The knobs are divided into sections: Oscillators, Waves, Mixer, Filter, Amplifier, LFOs, Modulation and Envelopes. With a few exceptions, anyone familiar with traditional subtractive synthesis should be able to find their way round instinctively (check out the panel in the photo). Some parameters, such as Wavetable Select and Startwave, are unique to Waldorf, so the provision of dedicated knobs is surely good news for those setting out to explore wavetable synthesis. The envelope section consists of eight knobs and a selector switch — these are the only multi‑function knobs, controlling the filter and amplifier envelopes and also the eight‑stage wave envelope and the free envelope. The rest are all pretty self‑explanatory with the exception of the two Modulation knobs, whic h control the amount of modulation used by the first two entries in the modulation matrix (if you remember from the Microwave II review, this stores up to 16 assignable routings). By careful programming, you can select the first modulation entry to connect LFO1 to overall pitch and the second to connect LFO2 to main cutoff frequency, and in this way recreate many traditional synthesizer routings without delving through the pages of parameters which aren't accessible via dedicated knobs.

External Audio Input

Turning to the rear of the synth (or the top, if racked) we see another important newcomer. Located in a convenient recess, past the dreaded external power connector, past the four assignable audio outputs, and next to the MIDI In, Out and Thru sockets is an audio input jack, by means of which you can process external signals using the XT's filters and effects. As on Waldorf's Pulse Plus, you must trigger the synth's filter and amplifier envelopes before you can hear anything. I'd like to see a 'static' mode similar to that of the Access Virus, so you could control the incoming audio's filter cutoff and resonance without providing a trigger. At present, only mono signals may be processed but since this input is actually a stereo connection (apparently two mono jacks would not fit on the main board), future operating system upgrades may give full stereo operation. I hope so, because the results I got feeding drum machines, samples and the like through Waldorf's selection of filters were very promising, although I felt the input sensitivity settings were a little coarse. If you want to dirty up a drum loop, the Microwave XT's Waveshaping or Sample and Hold filters are great starting points, and that's even before you even get to the onboard effects.


I have always found the Microwave to have a rich and complex raw sound, but felt that a modern synth should have some form of onboard effects too. I was, therefore, delighted when some rudimentary effects appeared in an earlier Microwave II/XT system upgrade. As well as Overdrive, Flanger and so on, the XT delivers Delay, Pan Delay and Modulation Delay from additional DSP memory. Though simple, these effects are handy, and Waldorf intend to extend their capabilities, for example by adding MIDI Sync to the delays. Unusually, delay times are shown in note lengths at a given tempo in bpm rather than in milliseconds. Original Microwave II owners (such as myself) miss out on the delay effects, but the good news for anyone purchasing a Microwave II as of today is that it is supplied with the necessary extra DSP RAM onboard as standard. Finally, if used multitimbrally, three patches keep their effects settings; the remainder may use only chorus. For an instrument with 10 notes of polyphony, this seems a workable compromise.


I've long been a devotee of the grungy Microwave sound, so please forgive any excessive gushing on my part. Its range encompasses squelchy analogue and hard digital with lots of weirdness in between, but it's never conventional or boring. The XT incarnation, with its external input and knobs, is the most tweakable and inspiring Microwave format so far, and making the knobs continuous is a brilliant idea for smooth changes during performance. And because they transmit MIDI controllers, I've discovered a variety of uses for the XT as a control surface while it's been here in the studio. In fact I've started to have little panic attacks already as I face up to the awful thought of returning the review model — some days this job is tougher than you imagine! If a Microwave has seemed tempting before but perhaps a little daunting, try turning a few knobs on this one.

Some Software

Microwave owners will be pleased to hear that a Windows 95 software editor/librarian is already available on the Internet. This shareware program handles all the Microwave's parameters and has a rather cool mix/morph/mutate feature to generate new patches based on two existing ones. If you want to create your own wavetables, the freeware programs Wavetowave and .wave+ offer the means either by additive synthesis (very cool) or interpolation between two waves.

Check out the programs at: (for the Editor)

(for Wavetable Creation)

Microwave XT Features

  • Two wavetable oscillators plus noise generator and ring modulator.
  • Oscillator Sync and FM.
  • 10‑note polyphonic, 8‑part multitimbral.
  • 256 User Patches, 128 Multi setups.
  • Arpeggiator forms part of patch meaning up to 8 simultaneous arpeggiators can run in multi mode.
  • Arpeggiator and LFOs can sync to MIDI clock.
  • Two filters with a total of 12 filter types.
  • DSP effects — the first three parts in a multi performance can use their full effects settings, the remainder are limited to chorus.
  • External signal input to filters/effects.
  • 65 wavetables plus 32 user wavetables.
  • 44 knobs, 9 switches, 2 x 40 character display, shift key, alpha dial.
  • All major parameters have a dedicated MIDI controller numbers.
  • Knobs send MIDI controllers.
  • Quite large (5 rack units).
  • And it's orange!


  • Lots of knobs — and they're all continuous so there are no sudden 'jumps' when you turn one.
  • Powerful wavetable synthesis with extensive modulation capabilities.
  • Excellent MIDI Spec — most parameters have dedicated MIDI controller numbers.
  • Now includes basic DSP effects which are maintained for up to three parts in Multi Mode.


  • External power supply.


In the previous Microwave review, I managed to think of two cons, but as one of those was "no effects", I'm grateful that Waldorf have kept the external power supply so at least I have something to gripe about! The XT offers all the swirly, dirty, sweepy sounds a Microwave can give with the addition of knobs and an external input.