Waldorf’s Microwave XT is a 5U rack mountable Wavetable synthesiser. When you see this synth, there are two things that immediately hit you. The first is the (revolting) bright orange paint job. The second are the 44 uncalibrated rotary encoders. This synth provides enough front panel controls to make even the most hardened synthesist happy for some time! The knobs are of the endless rotary encoder type. This means that they just continually spin round, even when you have reached the highest / lowest value for that knob.

The XT is designed to go in the rack. However, for those musicians who like to use their synth on a table, Waldorf have recessed the input / outputs, and sloped the front panel. This is an excellent design and one which means the rear connections are always easily accessible. Connections provided are MIDI in / out and thru, main outputs (stereo provided on two unbalanced jacks), sub outputs (identical to main outs) and an external input, provided on a single stereo jack. Please see later for more details of the external input.

The display is a two line LED display. This provides more than adequate space to display anything necessary. Names of functions are shrunk by a small amount, but are almost always still understandable from their cut down name (unlike on the Novation SuperBass Station, which condenses names to two digits!). The menu which you are viewing is selected from a panel of five buttons to the right of the main display. As you touch a rotary encoder, the screen displays its current value. This appears in the top right of the screen but the current menu remains fully displayed. This is a wonderful system, which works incredibly well. Once you get the hang of it, it becomes an incredibly flexible system. Underneath the display are four freely assignable knobs (control W - Z), which relate to the parameter displayed directly above it on the menu.

The sound generating part of the XT is a 64 part Wavetable. For those not familiar with Wavetables, this method of synthesis involves single cycles of waveforms, each assigned to a different slot in a ‘Wavetable’. Each of these sounds can be different, and by applying sweeps to the Wavetable, long evolving sounds can be created. The XT also has the ability for you to use less than 64 stages for the Wavetable (I assume that the minimum is a single wave at the start and a single wave at the end), in which case the machine will interpolate the waves in between. The last 3 (i.e. 62, 63, 64) slots of the Wavetable hold the ‘classic analogue’ waves, namely triangle, pulse and sawtooth. Each Wavetable oscillator (of which there are two) can have a different start wave, independent tuning and can have different amounts of the wave-envelope applied to it. OSC1 has a continuously variable FM (from OSC2) with a dedicated knob, and OSC2 can be sync'd to OSC1. Wavetable’s are selected from a large red multi-click knob in the middle of the oscillator section. Waldorf have provided 96 tables for use, but there are additional spaces for you to create your own Wavetables. However to do this, you will require an external editor, such as Emagic’s Soundiver. Wave table creation is a complex issue, but rest assured it is worth the work.

The next section is the mixer. Simple enough, this allows you to set the volume of OSC1 / 2, a ring mod source, and a noise source. From the mixer page, you can also adjust the volume of the external input, which can then be processed via the filters and envelopes.

The next section is the filter section. This is one of the most comprehensive filter sections that I have come across on any synthesiser. Here, you can set the cutoff, resonance (which self-oscillates at high values), envelope amount, velocity to envelope amount, keyboard tracking and more. You can choose from the following filter types :

Each of these has a distinctive sound and character. Most are fairly straight forward and work as expected. However, some are more complex, and require elaboration. These are :

Sin(x)>LP
12db/8ve Wave Shaper

The Sin(x)>LP filter has a sine wave shaper placed before a standard resonant LP filter. The Waveshaper filter is similar to the Sin(x)>LP, except that the Waveshape is no longer a sine wave, and is freely selectable from any of the available waves of the Wavetable currently being used.
Following the main filter is a second, less controllable filter which can be either Low pass or High pass at a fixed 12/8ve cutoff slope. This has resonance, but cannot self-oscillate.

Waldof have been generous with the envelopes that they have provided. There is an ADSR for the amplifier, an ADSR for the filter cutoff (which can be applied to other modulation destinations), and a multi stage envelope for controlling the sweep of the Wavetable. There is also a freely assignable ‘free envelope’.

LFO’s are also well specified, with two independent LFO’s, each with the same controls. From the LFO page, you can adjust the following :
Rate (in frequency initially, but if the LFO is sync'd to MIDI clock, this is displayed as musical values e.g. 1/8);
Shape (Sine / Triangle / Square / Sawtooth / Random / S+H);
Delay time;
Sync source - on (all LFO’s behave as one);
Sync source - off (all LFO’s free wheel);
Sync source - clock (all LFO’s sync to MIDI clock);
Symmetry and humanize.
LFO2 offers identical controls, but adds a phase option. This enables LFO2 to be controlled by LFO1’s cycle.

Hidden inside the menus there are some extra functions. The first of which is the effects section. This provides :

All of which operate much as expected. On thing that is slightly odd is the way the delay effects work. The Xt seems to be unable to allow you to just set a midi clock division of rate in hertz. You get this odd situation where it is a ratio of the incoming midi clock, but its resolution is so small as to be a joke.The next section is the Arpeggiator. This provides 15 presets and one user defined pattern (which has all the usual options for entering rhythms). It can be sync'd to MIDI clock and operates exactly as expected.

The final section is the modifier / modulation matrix. This is probably the most powerful part of the XT. Here you can apply an arithmetic operation to your control sources and then route them to various destinations.

The first part is the modifiers section. Here you can take two control sources (such as LFO1 and controlX) and apply an arithmetic operation to them, to modify each by the other. There are four of these modifiers.
Available modifiers for each slot are :

Comprehensive is the only word!! Arithmetic options can be applied to your modulation sources.
You could for example add together lfo1 and lfo2 then route this to the cutoff. Or you could determine which had the maximum value and then apply that to the resonance.
Available arithmetic operations are :

The Modulation Matrix is up next. Here you can route control voltages to destinations. Relevant control sources are the same as those detailed in the modifier section, but destinations are :

Waldorf have provided a generous amount of storage on the XT, divided across two banks, A and B. Each bank has 128 storage locations. To reproduce your sounds you have two choices. To use the instrument as a single sound source, simply dial up your sound in the SOUND mode. To use the XT as part of a multitimbral setup, you can use MULTI mode. There you can set up to eight sounds to play at once (although there are limitations in polyphony and effects usage in this mode), assign midi channels, set the output (main or sub outputs) etc. Up to 128 multis can be stored, but these do not save the programs associated with them. All programs and multis can be sensibly named due to the fact that names can be up to 16 characters long! Fantastic!

However, all this control would be for nothing if the synth still sounded terrible. This is the great news about the XT - It sounds like A MILLION DOLLARS. The sound generation system is one of the nicest that I have encountered, and the creation of complex pads or short staccato notes is enjoyably simple. The Waveshaper filters sound wonderfully crunchy, and the other filters are suitably squelchy. The envelopes are snappy at short times and smooth over long periods. Modulation is simple and extensive, with many parameters being syncable to MIDI clock (which makes for fantastic throbbing bass lines). The fact that all of the front panel knobs send and receive midi controllers, and many of the internal parameters can receive midi controllers is also outstanding.

But there are bad things within this synth.
The first is the filter section. At times (especially with fast sweeps with high resonance) the filter can sound overtly digital. You can hear the quantisation steps clearly. At lower resonance this is not so much of a problem, but it is still occasionally noticeable.

The second is the effects section. Firstly, the effects provided are fairly nondescript, and can easily be dispensed with. Secondly, there is an alarming tendency for the XT to appear to crash, if you change the settings in the effects pages whilst playing. Very bad! All sound from the XT mutes during these periods, until you change the effect type. Also the effects become limited when used within the multi pages and only the first three slots can use effects.

The last problem is the external input. Although in the manual it states that this is a stereo input, I have only ever managed to get it to work in mono. It can receive a stereo signal and output a stereo signal, but at some point the channels appear to be merged to a mono signal and then the same signal is output on both sides. I have a theory that this is because the output from the mixer (and therefore the input to the filter) is mono, and therefore the external input has its two channels merged. The external input is useful, if somewhat limited.

Overall though, the XT is one of my favourite synths. The sounds that come from it are simply stunning. It can imitate any other synth that you can imagine (not sure why you would want to imitate another synth, but I know some people like this kind of thing), and it is so controllable that it is a joy to work with.