Waldorf Miniworks

Now that Waldorf have released their 4‑pole filter as a stand‑alone unit, giving your digital synth an analogue spin is as easy as popping it in the Microwave. The result, as Paul Ward discovers, isn't always fast food.

No matter how good digital filters have become over recent years, the good old‑fashioned analogue filter still has that certain 'something', which keeps it tantalisingly out of reach of the digital domain. While many argue about the relative merits of the ARPs, Moogs and Oberheims of the past, one thing that most agree upon is that the character of the filter in such machines plays a large part in defining the character of the synth as a whole. Several manufacturers are now producing add‑on analogue filters which can bring the warmth and character of the analogue filter to our often anodyne digital synths. Waldorf are the latest.

The Waldorf Miniworks 4‑Pole is, as its name suggests, a resonant four‑pole low‑pass analogue filter, identical to that which graces the Waldorf Microwave. The four‑pole design results in a 24dB per octave cut‑off slope, which is arguably the most popular filter type for traditional analogue synthesizers. ADSR (Attack, Decay, Sustain, Release) envelope parameters are supplied for both filter cut‑off and amplitude. Reasonably complex modulation routings can be applied to affect cut‑off, resonance, volume and left‑right pan position, either from the in‑built modulation sources, MIDI controllers, the trigger envelope or the input signal envelope.

This all makes for a very flexible device that is as comfortable handling single‑ended noise reduction duties as it is adding resonant analogue filter warmth to a digital synth or sampler. Indeed, so keen are Waldorf to promote the 4‑Pole over a wide range of applications that they include several factory patches, and suggest configurations to generate auto‑wah effects, de‑noising, auto‑panning, compression, pseudo‑ring modulation and even pitch‑swept drum synth sounds (although when the world will ever be ready for those again, I don't know).

Ins & Outs

Input to the 4‑Pole is strictly mono, although a pair of outputs provide the ability to pan the incoming signal across the stereo soundfield, either at a fixed position or under the control of a modulator, such as the in‑built LFO, or MIDI velocity values. Alongside the audio input is the trigger input. This allows the use of an old‑style voltage trigger to fire the 4‑Pole's envelope generators. Our brief tour of the rear panel ends with a quick glance at the ubiquitous MIDI In/Out/Thru sockets, and a glimpse of the AC 9V power connector. Waldorf have taken it upon themselves to label the top panel above the rear connectors, so that you don't have to peer round the back of the unit, which is to be commended. Would that other manufacturers were so considerate!

The 4‑Pole has a grand total of 40 preset memories. The first 20 of these are available for overwriting by the user, whilst program numbers 21‑40 feature fixed factory patches. Programs can be selected by MIDI program change messages, or by a pair of up/down buttons to the right of the display. I can't help feeling that 20 user memories is a bit stingy by today's standards.

Programming of the 4‑Pole takes place over six 'Edit Levels'. To access each level, you are required to press the 'Mode' button, until the LED to the left of the required level is lit. Once the level has been selected, the four control knobs will affect the parameter in the column above it. Waldorf have opted to make the leftmost of the four controls a bright red, presumably to signal its use as the control which takes care of cut‑off frequency — arguably the most oft‑tweaked control on a filter. On some edit levels, the control knobs double up for two (related) duties, when used in conjunction with the Shift key. On Edit Level four, for instance, the second knob controls resonance modulation amount or, alternatively, selects the resonance modulation source when the Shift key is held down.

The knobs can be set to operate in 'Jump' mode (the current edit value immediately jumps to the absolute position of the control when it is first moved) or 'Relative' (moving the control to the left subtracts from the currently set value, whilst moving it to the right adds to the value). The fact that Waldorf have provided the option to work in either mode is excellent.

Wandering Hand Syndrome

Unfortunately, I found the programming interface made for a very trying experience. I just never seemed to be on the correct edit level for the task I was trying to perform. The relationship between cut‑off frequency and envelope modulation amount is pretty fundamental to many synth bass sounds (which must surely be a prime use for this type of device), yet I had to constantly flip around the six edit levels to make changes to them. The fact that the two parameters make use of the same control knob didn't help matters either — it's all so frustrating! I found myself hankering for a few dedicated controls just to reach out and tweak. The three‑character LED also struggles hard to provide the information necessary to keep on top of the 4‑Pole's programming system. I found the experience vaguely reminiscent of early digital drum machines. Some of the cryptic abbreviations had me reaching for the manual, until familiarity set in.

On the plus side, all control changes may be transmitted via MIDI for 'on the fly' editing with instant playback — just what the doctor ordered! Any single program, or all of the 4‑Pole's current data, may be dumped as MIDI system exclusive messages.

The 4‑Pole's envelopes can be triggered in four ways. In addition to the manual trigger button, MIDI note messages and the trigger input, the audio input signal can also be used as a trigger source. The envelope of the incoming signal can be used as a modulation source too, which is handy for creating auto‑wah or envelope follower effects. Other modulation sources include the internal LFO (with sine, triangle, saw, pulse and sample & hold waveforms), the VCF/VCA envelopes, MIDI keytracking and MIDI foot control (see 'Modulation Sources').

The Learning Curve

After my initial concerns over the programming aspects of the 4‑Pole, I was heartily cheered by the sounds emanating from it. This filter has a certain 'gloss' that I warmed to instantly. If I was to nit‑pick, it would only be to suggest that resonance feedback seems to 'jump in' over a small range of the control's travel: I'm used to a more gentle curve from my old analogue synths. This aside, I was engrossed for quite some time, adding resonant analogue punch to my favourite bass samples, and sweeping breathy choirs with a gentle LFO burble. For all its programming idiosyncrasies, the 4‑Pole certainly has it where it matters.

The 4‑Pole has one other piece of magic up its sleeve. Not only can the audio signal be used as a trigger and modulation source, but these two features are made available as MIDI output messages too. The audio trigger appears in the MIDI output as a note‑on message (the actual note value can be defined), but more importantly, the envelope of the audio signal can be transmitted as MIDI breath controller information. This is superb for translating the performance of an acoustic instrument into usable MIDI control data. I was able, for instance, to vary the volume of pad synth parts to an acoustic guitar according to the dynamics of the performance, and also to sweep the frequency of a notch filter from a spoken vocal track! The possibilities are, as they say, 'limited only by your imagination'.

Waldorf could improve the manual in many respects. Much information is sketchy, and in some cases — notably the Gain and Trigger level controls — totally absent! Mention is made of the factory presets with suggested configurations, but there's no explanation as to what each preset is meant to be, or the control settings that have been used to produce the effect. The five‑page glossary is a pleasurable exception to this criticism, however, with good, concise descriptions. The system exclusive information is also very welcome.

Summary

I wanted to like the 4‑Pole — I really did. The concept is spot‑on, and the sounds on offer are undoubtedly good — especially given the wide range of modulation options on offer. But I found the implementation very frustrating. I lost count of the number of times I was twiddling the filter cut‑off control, only to realise that I was in the wrong edit level! However, the discovery of the audio envelope‑to‑MIDI breath control feature went a long way towards mitigating such shortcomings.

If you are currently looking for an analogue filter to add to your armoury, then you owe it to yourself to give the 4‑Pole a chance. Whilst the user interface can be something of a pain, the quality of the filter is excellent, the modulation options are generous, and the MIDI specification is well beyond most others on the market. As to whether the plusses outweigh the minuses, that's something that only you can decide.