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MAM RS3; VF11 11-band & Warp 9

Resonator; Vocoder & MIDI Analogue Filter By Paul White & Mike Senior
Published February 2001

MAM RS3; VF11 11-band & Warp 9

Paul White and Mike Senior walk down three roads to filtery wierdness for cost‑conscious musicians.

The German manufacturer Music And More (MAM) produces a large range of useful processing and problem‑solving rack units for musicians working within budgetary constraints. This range now includes a number of inventive filter‑based modules: the RS3 Resonator, the VF11 11‑band Vocoder, and the Warp 9 MIDI Analogue Filter. These all share similar cosmetics and, like most of MAM's gear, use external power supply adaptors.

Re‑Resinator

MAM RS3; VF11 11-band & Warp 9

The RS3 Resonator retains a very similar functionality to the FAT Resinator reviewed back in SOS March 1998, but for those of you without that article to hand here's a quick recap on its facilities. Inside this lightweight 1U processor are three sweepable analogue band‑pass filters, whose frequencies may be controlled both from the input signal's own envelope and from that of an external source, as well as from two internal LFOs. The RS3 is essentially a mono‑input device, though a pseudo‑stereo output can be created by routing two of the filters to a pan control and keeping the third at equal level in both outputs.

Each filter has a separate centre‑frequency control, though the resonance of each is fixed at a value optimised for a classic filter‑sweep sound — while there is a front‑panel control labelled Resonance, this actually appears to mix the filtered sound with the unprocessed signal.

The essence of this unit is the way in which the filters are controlled. A first set of control signals is derived from the input signal using three independent, frequency‑selective envelope followers, each of which is fed from one band of a three‑way crossover following the input stage. These three signals control the centre frequencies of the filters, to a degree set by the Depth control in the Env Modulation section of the front panel — a polarity‑invert switch turns 'zweee' into 'eeewz', if required. To keep things simple, the attack times of the envelope followers are fixed, though the decay times are globally variable.

Even if you only modulate the filters using the Env Modulation section, you can quite easily get complex, dynamic filtering effects that change depending on the dynamics and frequency content of the input. However, the filter frequencies may also be modulated by a pair of onboard LFOs, to a degree set by a Depth control in the LFO Modulation section of the front panel. The frequencies of these LFOs are deliberately unmatched and can be varied together using the single Rate control — from extremely slow rates to around 2Hz. A mode switch beside the LFO controls sets the manner in which these LFOs affect the three filter frequencies: in Mode 1, all three filters are controlled from LFO 1; in Mode 2, LFO 1 controls filters 1 and 3 while LFO 2 controls filter 2; and in Mode 3, LFO 1 controls filter 1, an phase‑inverted feed from LFO 1 controls filter 2, and LFO 2 controls filter 3. While this arrangement doesn't always make for predictable results, the effects can be wonderfully dynamic and complex, yet still usably musical.

An external source can also be fed into the RS3, where another envelope follower derives a control signal which again affects the filter frequencies in either negative or positive polarity depending on the setting of a Depth control, this time in the Man/Ext Mod section of the front panel. This control sweeps the frequencies of all three filters manually if nothing is connected to either the front‑panel or back‑panel external‑source input sockets.

Eleventh Heaven

MAM RS3; VF11 11-band & Warp 9

The VF11 Vocoder is an 11‑band vocoder combining ease of use with flexibility. A vocoder works by superimposing the frequency response of one signal arriving at an analysis input (typically a voice) onto another arriving at the synthesis input (such as a rich synth pad). Appropriately, the back panel of the VF11 features an Analyse section, which accepts line‑level signals on a quarter‑inch jack or mic‑level signals on an XLR, and a Synthese (sic) quarter‑inch jack input — though it's worth noting that no phantom power is available from the XLR mic input. The way in which the VF11 produces the characteristic vocoder effect is by feeding each signal to its own 11‑way crossover, and then adjusting the level of each band of the synthesis crossover in accordance with the level detected at the output of the equivalent band of the analysis crossover. This means that an output is only produced when a signal is present at both the analysis and synthesis inputs, and that the signal at the synthesis input should be harmonically complex to get the best results — the filters which create the vocoder effect can only subtract harmonics, not add them.

If no synthesis input is connected, an internal sawtooth VCO is activated, the frequency of which is adjustable from a front‑panel VCO knob. This provision makes it easy to set up robot voices — most notably, of course, the Cylons in Battlestar Gallactica! A compressor following the analysis input is also provided, in order to prevent overdriving and to keep the vocoder effect as consistent as possible.

The front panel has two knobs to adjust the overall input gains of the analysis and synthesis signals respectively (with simple peak LEDs to warn of overloads), and also has separate gain controls for each of the 11 synthesis crossover bands — these function somewhat like a graphic equaliser, allowing the tonal balance of the vocoded signal to be adjusted. The Output Mix section comprises four knobs. The Analysis and Synthesis controls adjust the level of each of the input signals reaching the unit's output, while Vocoder adjusts the overall output level of the synthesis crossover. Filter applies an offset to the crossover control signals which allows each band to remain partially open even when no analysis signal is present, thus allowing fine tuning of the effect's sensitivity.

An important feature of any vocoder is the way it handles sounds which rely on bursts of high‑frequency noise, such as the 'F', 'T' and 'S' sounds in speech. Most musical signals which tend to be fed to the synthesis crossover will not to have sufficient high‑frequency energy to render fricative and sibilant sounds in the analysis signal intelligible. To get around this, the VF11 has a circuit that detects voiced vocal sounds, and which inputs white noise to the synthesis crossover whenever they are absent, making unvoiced sounds much more intelligible. The detection circuitry can be adjusted via two rear‑panel trim pots, but in most cases it will be best to leave these as set. If you wish, you can use an alternative sound source in place of the internal noise source, by feeding it to the rear‑panel Unvoiced In quarter‑inch jack socket. The level at which the noise source or substituted external signal feeds the synthesis crossover can be set using the front‑panel Unvoiced Level knob, and a detector LED shows when unvoiced components are being added.

Warp Factor 9, Mr Sulu!

The Warp 9 MIDI Analogue Filter is a rather sophisticated analogue filter with a number of triggering and modulation options, including the ability to trigger from the envelope of the incoming signal and from MIDI Note On messages. There's also a VCA section that may be modulated, followed by a distortion circuit which can be switched in or out. Both the input and output are on mono unbalanced quarter‑inch jacks and there's a full set of MIDI In, Out and Thru connectors.

The filter at the heart of the Warp 9 is a traditional 12dB/octave design with Cutoff and Resonance controls. It can have a low‑pass, high‑pass, band‑pass or notch response, selectable using a front‑panel Mode switch. There are six possible modulation sources for the filter cutoff frequency: the manual Cutoff control; an internal LFO with a choice of waveforms including sample and hold; an envelope follower which tracks the input signal; and three MIDI messages — Continuous Controller 104, Mod Wheel (Continuous Controller 1) and Note On.

The audio input's envelope follower (in conjunction with a Trigger Level knob) or MIDI Note On messages can be used to trigger a fully adjustable internal ADSR generator with variable start time delay and depth control (labelled Env Mod). In the case of Note On triggering, there's a choice of single or multi‑trigger modes. Clearly the two types of triggering can't be used at the same time, but the LFO may also modulate the filter in either mode. As an alternative to triggering the ADSR with your MIDI Note On messages, you can also get the filter to respond to the velocity and keyboard position of each note.

Although the WARP 9's filter is analogue, the control system is digital, programmed using the five knobs in the Modulation 1 section of the front panel together with a small switch that cycles them between three banks of functions. Corresponding LEDs let you know what bank you're in, though the physical position of the knobs may not correspond to the actual setting of the parameter being addressed, given that the controls are assignable.

A major advantage of the digital control system is that a number of front‑panel settings, such as Cutoff and Resonance, can both send out and receive MIDI data in real time, allowing you to record a filtering 'performance' on the fly and then edit it from within your sequencer. Another advantage to this system is that is affords considerable modulation flexibility, providing some entertaining possibilities if you feel like delving into the manual. One interesting option is the possibility to modulate the ADSR release time from the LFO, and there are a number of innovative ADSR triggering modes available. There are also a few concealed options for sync'ing the LFO's operation with tempo, if that's what you're after.

The VCA section of the WARP 9 can be triggered via MIDI or from the input's envelope generator, though the way this occurs can be selected from a number of options. For example, the VCA can be programmed to act like a gate which opens whenever the signal is above the threshold set using the Trigger Level knob, or it can be programmed to stay permanently open regardless of the input signal level. In addition to any triggering, the VCA may also be modulated using the internal LFO and MIDI Continuous Controller 113.

Up to 32 user programs may be stored, and can be recalled under the control of MIDI Program Change messages. As there is no traditional display, the program numbers are shown as a binary sequence on five of the status LEDs — a similar binary counting system is used to select the MIDI channel.

Zwee‑some Threesome

The RS3 doesn't lend itself to creating precise effects, but rather tends to go off and do its own thing based on the character of the input signal. It's easy to set up — even though I couldn't understand the text of the review unit's brief German manual, the included block diagram explained the operation pretty well. What's more you can make big differences to the sound by varying the overall brightness and filter release times, as well as by controlling the degree of LFO modulation. Even though there's no MIDI and the filters are band‑pass with few adjustable parameters, somehow the results always manage to sound both interesting and musical. The pseudo‑stereo effect is also a big plus, transforming a boring mono signal to a swirling stereo soundscape at the push of a bypass button. What more could you want?

As for the VF11, you have to be sure to set the input levels reasonably accurately, by getting the peak LEDs flashing briefly on peaks, if you're going to achieve a good result. Once this is done, you can create the textbook 'talking instrument' vocoder effect, using a voice and a rich synth pad, simply by setting the Unvoiced Level knob and all the individual band level knobs to the centre of their range. It can help to make the effect even clearer if you advance the Filter control until you can just hear an output without speaking into the mic, and then back it off just a fraction until the output is silent — this effectively achieves the optimum sensitivity setting for conventional vocoding. Being able to mix the unprocessed input with the vocoded output adds to the overall flexibility of the device but, for classic vocoding, only the vocoder level control should be turned up.

The VF11 performs its job effectively and is also not difficult to set up. There's lots of scope for creating new effects by using sounds other than speech at the Analysis input, but there's no way to cross‑patch the different frequency bands as there is in some high‑end models. Mangling drum loops and synth pads together can be both fun and productive, though it's difficult to think of many truly original ways of using the classic vocoder effect. Bottom line is that if you need an affordable vocoder, and you want to use hardware rather than a software plug‑in, the VF11 does the business.

The Warp 9 is a much more sophisticated device than the RS3 and VF11, and has many features that are not obvious when you first start to play with it, so some experimentation is essential if you're to do more than create basic filter sweeps. Given the somewhat cryptic control setup, this will probably mean having a good look through the manual. Tonally, the filter is rich and interesting sounding, and I found it great for adding synth‑style filtering to instruments without filters of their own, such as the original Emu Proteus range or the Kawai K1. However, the weakness of any filter like this is that its response to polyphonic inputs can never be the same as that of a real polysynth, as those instruments have separately triggerable filters for each voice. Used creatively, however, the Warp 9 provides a cost‑effective way to add interest to synth sounds, samples and loops, and the comprehensive LFO options ought to provide lots of creative possibilities for exponents of electro‑pop or dance music.

Given the extremely competitive pricing which Music And More have adopted, there is little in the way of direct competition for the RS3, VF11 and Warp 9, the closest rivals being the Electrix range, in particular the £199 Filter Queen and EQ Killer. These are stereo units and are much more sturdily built, but they can't really match the MAM units in terms of sheer features, particularly the Warp 9. As such, all three MAM units deserve to sell well to anyone who wants to throw filtering restraint to the winds, whilst remaining within a tight budget.

Pros

  • Musical sound with a lot of stereo movement.
  • Cheap!
  • Easy to get useful results.

Cons

  • Outcome not always predictable.
  • Filter parameters are a little restrictive.

Summary

A fun filter box with a difference. Good for textural pads and swirls as well as techno loops.

Published February 2001