Waldorf Rocket Desktop Analog/Digital Synthesizer

The synth is divided into four sections and, whether you're a novice synthesist or an old campaigner, it's practically impossible to get lost, or make worthless sounds. There's only one way to produce no sound at all, and even that has its uses!

I sensed more than a whiff of TB303 about the Rocket design, from its square/sawtooth switch to its pared-down envelopes. The choice of waveform determines the functionality of the Wave and Tune knobs, each marked with intriguing hieroglyphics. If you begin with a square wave, the first half of the Wave knob's rotation sets the pulse width. At its absolute minimum, the width is so narrow it disappears. Without a level control or mixer, this is the recommended way to deactivate the oscillator, something you'd probably do when using the filter's audio input. Resisting the lure of external processing for a moment, let's keep turning that Wave knob. From 12 o'clock onwards, pulse-width modulation is introduced, the depth gradually increasing until, in the last part of its travel, the modulation speed is also hiked up. That's a heck of a lot of sonic variation squeezed into a single control, but it's typical of the Rocket that it feels 'right' very quickly.
Staying with the square wave, the Tune control brings its own innovations. The left part of its travel introduces a copy of the oscillator. At first, this is subtly detuned, but it's not long before all subtlety is dropped. Passing through the middle of the knob's travel and onwards, this newly added oscillator slips into various intervals, such as fifths, octaves and others. In this way, the Rocket covers much of the ground that two oscillators typically would, from the minimum of controls.

Flip the switch to sawtooth and you are treated to a different set of options. At anywhere before 12 o'clock, the Wave knob activates 'Saw Sync Mode' and, with it, further oscillator multiplication. Turning the knob clockwise has the effect of shortening a hidden envelope that's wired to produce sync sweeps. Over the course of its travel, the sweep is gradually reduced to a mere blip, while the Tune control sets the frequency of the slaved oscillator. The end result is a wonderful, zappy and ripping sync implementation that I, for one, didn't see coming.

The interface isn't perfect, though. For example, to select only a single sawtooth oscillator, the Wave knob has to be at its exact centre position. Finding this position isn't always instant, because it only occupies a small proportion of the knob's travel. Still, it's not a great inconvenience. Continue turning the knob clockwise from the centre and additional sawtooth waves are generated: up to eight of them.

The Tune knob operates differently for the sawtooth wave, substituting pulse-width modulation with different intervals and even chords. The number of notes included is set by the Wave knob, and some of the resulting chords are quite complex and interesting. I found that it was often a case of playing it by ear, because it was hard to judge by eye which chord would correspond to each knob position. Actually, with both of these controls it was sometimes more predictable to dial in values from a remote MIDI controller — heresy, I know!

Finally, there's a special sawtooth unison mode that's brought to life when both the Wave and the Tune knobs are at their rightmost positions. All eight sawtooth oscillators are now distributed evenly amongst the notes played. A single key can therefore produce the rich, slightly detuned sound of eight voices layered together. At the other end of the scale, you can play huge eight-note chords. Waldorf are keen to point out that this is paraphony and not true polyphony, because it's only the oscillator that can multiply itself in this fashion, not the filter or envelopes. It's a compromise, but one that worked for synths like the Korg Poly800 and MonoPoly. Being able to switch from an ostensibly monophonic synth to one capable of pads and stabs is a joy not to be lightly dismissed. The final oscillator control is glide and it's activated when you play legato.

The filter is a 12dB, multi-mode, state-variable design, its band-pass and high-pass modes ideal for classic trance leads or for slimming down the Rocket's pseudo-polyphony. With no discernible zipper noise and a lively resonance, this is a fab-sounding analogue filter. In low-pass mode, it delivers acid bass lines effortlessly from a single saw or square wave, a touch of envelope modulation and the snappy decay. Filter envelope amount is the only Rocket knob driven by incoming velocity, but as this is the optimum setting for accents anyway, it earns a thumbs-up from me. A rocker switch selects the filter type and a second switch offers filter tracking of zero, 50 and 100 percent. With a setting of 100 percent and resonance pushed into self-oscillation, the resulting sine wave tracks smoothly over at least four octaves; enough for it to count as a sound source in its own right.

Flip the Boost switch and the filter changes from Dr Jekyll to Mr Hyde. This on/off saturation effect is just the ticket for adding bruising harmonic distortion, and although its amount is fixed, its contribution varies with the level of resonance and whether chords are played. It can get quite strange and ugly in the latter case.

Sportingly, the Rocket's filter and overdrive are accessible to external signals, the only proviso being that you must trigger the envelopes with notes or the Launch key. There's no attenuator for the audio input, but line-level signals are handled well enough. Now's the time to select a square wave with a width of zero, assuming you don't want the oscillator splattered all over your audio processing. Shaping all that filtery goodness into basses and leads, there's an envelope shared by the filter and the output stage. It consists of two switches and a decay knob; attack is always instantaneous. You could view this either as an homage to the TB303 or as an unnecessary limitation, but when I queried if attack could be added later as a MIDI CC, I was told "that's just how it is”. The switches determine whether the release time follows the decay or is zero — happily not a clicking zero like Korg's Monotron range. When both sustain and release are 'on', the envelopes work in single-trigger mode.

At the Rocket's left-hand side are the knobs and switches of the combined LFO and arpeggiator. The LFO Target switch selects modulation of either the pitch or filter cutoff, or engages the arpeggiator. There's not a lot of explanation necessary about either mode. The LFO has three waveforms — triangle, sawtooth and square — and its range is from 0.05Hz to 50Hz. At its very minimum, the LFO effectively stops and generates a random value each time a note is triggered. This isn't quite as desirable as true sample and hold, but it's definitely useful. The LFO syncs automatically to incoming MIDI clock, and occasionally I wished there was a way to deactivate this and let the LFO run freely. At present, the only way to accomplish that is to interrupt clock transmission.

When the Target switch is set to ARP, the arpeggiator is engaged, or should be. The review model wasn't having any of it, despite my sending the appropriate MIDI CCs (in case the switch was busted). It turned out to be a bug preventing the arpeggiator from working unless the Rocket was set to MIDI channel 1. Waldorf are aware of the problem and say that a fix is in progress. The arpeggiator's range is four octaves, and as well as up, alternate and random directions, it has eight rhythmic patterns, some of which introduce glide.

Connect the Rocket to a computer via USB and not only does it hurl MIDI in both directions, it draws power too. In a computer-free setup, the same USB cable plugs into a universal adaptor and gets its juice that way. For lovers of traditional five-pin MIDI, the standard In and Out connections are present, but there's no Thru. In order to assign the MIDI channel, you poke a recessed button with a pen while sending MIDI data. The Rocket duly extracts the channel and stores it until you repeat the process. Almost every control has a documented MIDI Continuous Controller, and not only does the synth respond to these when received, they are also transmitted from the MIDI and USB ports as you turn knobs and flip switches. However, given the lack of a physical volume control, it's odd that the synth does not respond to any volume-related CC. Nor does it offer external control of the Boost or filter Type switches. This seemed to be an oversight because you can otherwise program the entire synth via CCs. In fact, the Type and Boost switches are hard-wired directly and there's no way to prise in any MIDI control, so it's down to the user to manually adjust these two switches.

Waldorf Rocket Desktop Analog/Digital Synthesizer Features:

• A powerful combination of digital oscillators and analogue multi-mode VCF
• Has a limited but welcome ability to play chords
• Can process external signals via its filter and overdrive
• Extensive MIDI control
• Some limitations: for example, no volume control, attack is fixed, several key parameters not MIDI controllable
• Knobs not the highest quality