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Waldorf Pulse

Waldorf Pulse

A monosynth that doesn't cost monopoly money? Paul Nagle thinks Waldorf's new Pulse offers the most fun you can have with your presets off...

There's something about a classic analogue filter sweep that still sends a shiver down my spine. Even in these days of realistic choirs and cold digital bells, there's a special, almost organic quality to those old electronic sounds. It was with genuine interest, therefore, that I welcomed Waldorf's latest offering — a 2U, rackmounted monosynth called the Pulse — into my humble abode.

The Pulse features three analogue oscillators, an analogue noise source, two low frequency oscillators, two ADSR envelopes, a powerful resonant low pass filter and a flexible modulation matrix. Performance tools include portamento, and an arpeggiator which can sync to MIDI. But the absolute killer feature is that every parameter change generates (and responds to) MIDI controller messages.

Layout

One of the first things that strikes you about the Pulse is its physical depth (sadly not immediately apparant from the picture accompanying this review); it's almost as deep as it is high, lending it the appearance, cuteness and charm — though sadly, not the taste — of a large rectangular Toblerone. Furthermore, the grey chassis and white/orange lettering recall the mighty Wave or Microwave, and indeed, anyone who has programmed the latter will be instantly at home with the Pulse's matrix method of parameter access: a mode button steps downwards (upwards too would have been nice) through six levels, current position being indicated by a green LED. Six knobs are then used to access the options on that level. These are reassuringly solid; more substantial than those on, for example, the Korg Prophecy. An additional six levels are accessed using the shift key (and the relevant LED flashes to remind you of the fact). Overall, navigation is both simple and effective.

Presumably to keep costs down, the Pulse has no LCD. Instead, a small 3‑character readout shows all status information. Initially, I felt this was a shortcoming, but soon decided it didn't make much difference to the use and programming of the synth. Indeed, the status was actually pretty clear when compared with most tiny 'letterbox' displays. My only lingering reservation is with the method of checking existing values by holding the mode button and twirling each knob. This is cumbersome, requiring two hands for the rightmost controls. Also, there is no overview of all current settings, such as would be possible with an LCD. A temporary edit buffer ensures that if you change patches mid‑way through creating that kickin' bass, you won't lose a thing: simply return to it and carry on. The edit buffer is lost if you start to edit a second patch before saving the first.

No LCD means patch numbers, not names. This is not so bad as it might sound — at least you are spared the bother of thinking them up in the first place! Don't look for an on/off switch, headphone socket or dedicated volume control — Waldorf have concentrated on the things they consider important, and dispensed with the stuff they don't. Completing our quick tour, the back panel holds the obligatory three MIDI sockets, 12V power input and stereo outputs. Although the review model was powered by a 'Euro‑type' mains adapter, I am assured production models will feature an anglicised plug.

For me, the only real downer was the fact that of the 99 patch locations, only the first 40 are user‑programmable. I queried this with Wolfram Franke of Waldorf, who said it was due to the processor used, and that the addition of more RAM would have required a dedicated memory management unit, significantly increasing the price.

Waldorf Pulse: No LCD means patch numbers, not names.

Road Test

Flipping through the factory sounds was a puzzling experience. Several conventional (and usable) analogue patches are intermingled with many wailing, ring‑modulated and discordant offerings, often quite low in volume and brimming full of portamento. I checked to see whether the review model's brains had somehow become scrambled, but apparently Waldorf's idea was to show that the Pulse is not simply another TB303 clone capable of only bass sounds. They certainly made their point! I think that filling the permanent memory locations with more conventional fodder (and the user locations with the weird stuff) might have been a better way of attracting the masses. Nevertheless, it's a brave move in these days when everyone's so used to relying on presets (would Korg have sold so many Prophecys had they followed the same philosophy, I wonder?).

Fortunately, programming is a breeze, and in no time at all I was able to create interesting, overloaded lead sounds reminiscent of the Microwave, as well as recreating many of my favourite, old‑fashioned synth timbres with remarkable accuracy. Just a few edits away were rich filter sweeps, beautiful solo patches, chirpy sequencer fodder, lush pulse width modulations, clangorous noises, warbly 'shooting star' sounds, rumbling thunder, thumping basses and dynamic sync leads.

The Pulse's repertoire is impressive, ranging from conventional analogue through to complex stuff that might have been knocked up on a modular system with yards of cable and a ladder. If you're stuck for a sound effect or two, selecting a program beyond 99 generates a random patch each time, and while these tend towards the wild and frightening, they can provide fun starting points. Oh yes, and you can make it sound like a TB303 if you really want to...

In Control

Once I discovered that the Pulse has allocated discrete MIDI controllers for every parameter, I sat with a silly grin on my face for a few moments, before connecting its MIDI Out to my sequencer and launching into an orgy of knob‑spinning. I can happily report that all edits played back perfectly, with every change I made being faithfully reproduced.

I then proceeded to create a complete Cubase mixer map in just over an hour — imagine doing that on your first day with a new instrument, after getting your head round the intricaces of its SysEx codes! This feature has wide‑ranging implications for creative MIDI sequencing, harking back to the simplicity of recording synths on tape. It makes the Pulse an incredibly expressive tool if driven by the right controls. If only all my MIDI gear was so accessible...

The three oscillators feature sawtooth, pulse and triangle waveforms, with oscillators one and two having variable pulse width, and oscillator two having sync and cross modulation. When sync is on, oscillator two is slaved to three, giving free rein to all those familiar grungey solos and basses. Cross modulation can be used to generate the unusual harmonics and clangorous tones associated with FM synths.

The oscillators, along with a rather harsh‑sounding pink noise source, are blended in a mixer section which is designed to be overdriven. Balancing levels requires a little practice, but a master output is available to even things up. I found that some noise was evident if oscillator levels were low, and the master output at maximum — see 'A Word From Waldorf' for an explanation of this.

The two envelope generators are the traditional ADSR variety — my favourite kind. They are simple to set up and understand, and can be combined in the modulation matrix with other sources for maximum flexibility. With an attack time of 1.9mS, the digital envelope is great for those punchy percussive patches, and must rate as one of the snappiest on an analogue synth. Compare this with the Marion Prosynth, which has an update speed of 16 to 22mS! Envelope one is intended to be used for the filter, whilst envelope two is aimed at the output contour. Each envelope has its own keyboard tracking rates and four triggering modes, allowing for the envelopes to shorten or lengthen depending on keyboard position, and to be retriggered according to playing style. The different triggering modes allow the envelopes to be restarted completely for each key depression, either at the current level or from zero.

It is probably fair to say that most analogue synths stand or fall by the quality of their filters, and Waldorf listened to everyone's "make it like a Minimoog" comments, added a little extra stability, and produced their classic, true analogue 24dB model. The Pulse is blessed with this, and I have to report it is a joy to use. It is rich and responsive, breaking into self‑oscillation at high resonance values, and creating a pitched tone which can track across the full MIDI range. Two low frequency oscillators are provided for those cyclic modulations — remember that if you wanted vibrato on the Minimoog, it cost you a regular oscillator.

On the Pulse, LFO 1 features sine, triangle, sawtooth, pulse, sample and hold (random), whilst LFO 2 features just triangle — but has an additional delay feature. Without using precious modulator routings, there is no way of gradually introducing the delay — you wait the allotted time, it starts, end of story. Similarly there is no way of sync'ing the LFO start cycle to note trigger — the LFOs are free‑running all the time, so you can't use them as predictable sources of additional modulation. If you want a pitch swoop at the start of each note, you'll need to use one of the envelopes.

On A Bender

Although monophonic, the Pulse has two outputs. This isn't quite so wacky as it sounds, as you can set up a modulator, say an LFO or envelope, to automatically pan the sound or choose from the whole gamut of benders, wheels, aftertouch and so on — definitely worth the two mixer channels if you can spare them. Portamento comes in two flavours: normal (it's on for every note) and fingered (on when you play legato). Let's hope this finally marks the end of that awful period in synth history when portamento and resonant filters were the exception rather than the rule!

Waldorf Pulse rear panel connections.Although monophonic, Pulse has a stereo output.

The Global section includes obvious stuff like MIDI channel, unit ID (device identification used in SysEx transmissions), master tuning and the definition of the additional MIDI controller. Pitch bend scales are set per patch, as are arpeggiator settings. Another welcome return, the arpeggiator, is not so complex as that of the Korg Prophecy, nevertheless it can sync internally or to MIDI clock, and can be stepped at different time intervals up to 32nd notes, with triplet options and an undocumented range of 16 pattern variations. An overall range of up to 10 octaves and all the expected up, down, alternating and random settings are present too.

The preliminary manual supplied with the review model was basic but adequate. Indeed, the Pulse is the sort of synth that you want to program right away, ignoring the manual completely (another clever ploy involving those strange presets!). I felt rather foolish having excitedly scribbled down all the controller codes I generated, only to discover them printed neatly in Appendix B!

The killer feature is that every parameter change generates (and responds to) MIDI controller messages.

Conclusion

Okay, we're talking about a module with no effects, no LCD and capable of producing just one note at once. Many people will reject it out of hand. For myself, I'd rather have a synth that can produce one good note rather than eight (or more) boring ones. It compares well with most old analogue synths you're likely to find, and it talks MIDI very fluently indeed. If you're after a well‑specified, eminently controllable synth that'll give you all those analogue sounds of yore without the need for an expensive retrofit, do check out the Pulse — but make sure you don't just listen to those 'unconventional' presets. As for this one — oops, I seem to have accidentally welded it into my rack!

Many thanks to Wolfram Franke of Waldorf who provided valuable insights and technical background to this review.

Beating The System

Recording SysEx messages can generate a lot of MIDI data and cause timing problems in dense MIDI streams. Control changes are far more economical, and with the Pulse it is a simple matter to fully program the synth directly from a sequencer, merely by sending the appropriate codes — even down to the arpeggiator settings. My only complaint was that I thought you ought to be able to send all current controller values, but it seems that this too has been thought of — Waldorf tell me you simply carry out a Program dump request with the header string $4b to do just this.

Words From Waldorf Designer Wolfram Franke

I contacted Waldorf designer Wolfram Franke with a couple of technical queries during the course of this review, and he offered some interesting insights into how certain aspects of the Pulse were designed, which are reproduced here.

"Our first consideration was how many oscillators a synth should have. One oscillator is boring; you can't create, detune or transpose effects. Two oscillators are better, because you have lots of possible ways to detune or transpose them, or to use different waveforms. But you have one problem. If the phase of one oscillator is shifted by 180 degrees to the other, you will lose sound. This happens every now and then, when you simply detune oscillators by a slight amount. But if you add a third oscillator, it fills these small silences, and the sound gets much richer and fatter. Also, a third oscillator is useful if you plan to offer oscillator synchronisation, cross modulation and so on; you'll still have one oscillator left for doing interesting things. So, the Pulse had to have three oscillators! However, the three waveforms are made differently, and only have one thing in common — they aren't processed by a D/A converter. The oscillators are not digital, but analogue. The pulse waveform is controlled digitally; the clock stipulates when the pulse waveform has to be at its maximum or minimum point. If you use pulse width modulation or cross modulation, this is also generated by the clock itself. The clock has only a 0 and 1 position, so the Pulse's cross modulation is mathematically identical with ring modulation. The sawtooth waveform is voltage‑controlled; the voltage is generated from the D/A‑converted clock signal, with additional parts creating the ramp. The triangular waveform is the most complex one; it's a combination between the sawtooth waveform and additional parts that process the down‑ramp.

"We then thought about what the oscillators should be capable of. Our first thought was pulse width modulation, and that's easy to implement, so we did it. Oscillator synchronisation, on the other hand, is not that simple to develop, but nicer than pulse width modulation, so, we put that in too.

"If you ask musicians about the ideal filter for a synthesizer, you almost always get one answer: the Minimoog filter. Its warmth and timbre are the best you can have. But the filter of the Minimoog is not perfect. After a couple of minutes it starts to detune, due to the heat it produces. Also, it's not possible to put it on 'keyboard follow' perfectly. So we only used the idea of the cascade circuitry, and used better parts around it. The result is a filter that, if it is tuned once, stays at its pitch and gives you a keyboard follow range of around 10 octaves without detuning.

"Furthermore, the filter changes its timbre when you slightly increase the input volume. The oscillators start to affect the cutoff frequency and the resonance response. This gives a wide range of characteristics simply by lowering or increasing the oscillator volumes in the mixer. Very low volumes produce a Roland‑like character, while higher volumes result in a more Minimoog‑like tone. The filter is voltage‑controlled, as you can see from the front panel. But we made sure the voltage is 100% stable in any situation.

"On the output and amplifier front, a Waldorf synthesizer has to have a fully‑controllable stereo output, even if it's monophonic — so we built a stereo output into the Pulse. You've mentioned in your review that you can hear noise when a note is pressed with oscillators low or not running. This is caused by the cascade filter and the mixer preamp. The cascade filter runs at a very low volume level, so it has to be amplified afterwards. This results in noise which could only be reduced by a noise gate, which we didn't want in the Pulse itself, because it would produce small clicks. We decided to go with the small noise, and its interesting possibilities.

"Digital machines and digitally‑controlled analogue synthesizers always suffer from one problem: they are slow at processing modulation, either digital or analogue. On the Pulse, we developed control voltage generators that are really fast. The modulation update is 523 times per second, which means that each modulation gets updated every 1.9mS. This gives you envelopes with analogue feel and digital control."

"What goes for the envelopes is also true for the LFOs. They are generated with the maximum update rate of 523Hz. To have one maximum and one minimum peak for each LFO cycle, you simply divide the update rate by two, and get the maximum LFO speed of 261Hz. If you look at this number, you find that it is a C3 on your keyboard. You can also modulate the LFO speed by keytrack, which enables you to play it melodically, remembering that 261Hz is still the maximum LFO frequency.

"Waldorf MIDI synthesizers have to have a full MIDI implementation, including parameter change send and receive. To give the user the easiest access to these parameters, we found that controllers are the best solution. Also, we implemented some features that should be found on other synths, but weren't implemented. For example, a MIDI tuning request. If the Pulse receives this message, it tunes the filter. Also, if you tune it manually (by pressing Shift and Mode, stepping with program up to 'tun' and again pressing Shift and Mode), it sends a MIDI tuning request on the MIDI Out. Real‑time control of the arpeggiator is also quite nice, so we implemented that as well."

"As for the future; well, upcoming developments for the Pulse will probably include a CV/Gate output, either as a hardware upgrade, or as a Pulse MkII."

Modulation Matrix

As well as hard‑wiring some of the more obvious modulation connections to filter, amplifier and pitch, the Pulse has four extra independent modulation sources (they're printed on the front panel, see right), which can be any of the following:

MODULATOR SOURCE

  • Off
  • LFO1
  • LFO1 & Mod Wheel
  • LFO1 & Aftertouch
  • LFO2
  • LFO2 & Env 1
  • Env 1
  • Env 2
  • Velocity
  • Keytrack (note number)
  • Pitch follow (note number but with portamento)
  • Pitchbend
  • Mod Wheel
  • Aftertouch
  • Breath Control
  • Control X (globally defined additional controller)

MODULATION DESTINATIONS

  • Pitch (overall)
  • Osc1 Pitch
  • Osc2 Pitch
  • Osc3 Pitch
  • Pulse width 1
  • Pulse width 2
  • Osc 1 level
  • Osc 2 level
  • Osc 3 level
  • Noise level
  • Cutoff
  • Resonance
  • Volume
  • Panning
  • LFO 1 Speed
  • Mod 1 Amount

As you can see this is a flexible, if not infinite, list. Up to four modulation routings can be set up per patch — perhaps you would want to modulate resonance with the mod wheel, pulse width by envelope 1, Oscillator 3 level by keyboard position and panning by note velocity. No problem. If we remember that all parameters (including the modulations described) can be changed directly by their respective MIDI controllers, then there really are few practical restrictions.

Pros

  • Great range of analogue sounds.
  • Every program parameter accessible directly by MIDI Control Changes — that's every parameter!
  • You don't need to bother searching out ageing second‑hand relics with no guarantee they'll last longer than a week. With a Pulse, you have the best of both worlds!

Cons

  • Wall wart power supply.
  • Only 40 user memories.
  • Three‑character display gives no 'instant view' of current settings.

Summary

Don't let the strange factory sounds put you off — this is an excellent monosynth module which can deliver first‑class analogue sounds. The capability to send and receive MIDI control changes for every parameter rather than SysEx makes it incredibly versatile, and full of possibilities.

Information

£599 including VAT.

www.waldorfmusic.com

Published February 1996