Reviews

In my humble opinion, most of today's instruments and signal processors are boring. They are boring not just in an understated way, but rather in a grand, epic, sweeping, Ben Hur sort. of way that screams, "Lack of imagination!" Many devices are devoid of sonic character and personality, with manufacturers choosing in stead to focus on churning out endless cookie-cutter copies of previously suc cessful ideas.Therefore, equipment design that imbues the gear with creativity, innovation, and the personality of the de signer is especially valuable. Because of the unpredictable economics of this approach, however, most of the un usual, quirky, and interesting instruments and processors tend to come from smaller companies.Sherman Productions is one such company. A tiny Belgian concern employing fewer than a half dozen people, Sherman has come up with a unique and powerful filter box that has nothing to do with trendiness, offering instead a vast (and, frankly, dangerous) array of sounds.





	ELECTRONIC MUSICIAN (U.S.A.) March 1999 SHERMAN FILTERBANK : Warning! This effects processor is not for the fainthearted. By Peter Freeman

	In my humble opinion, most of today's instruments and signal processors are boring. They are boring not just in an understated way, but rather in a grand, epic, sweeping, Ben Hur sort. of way that screams, "Lack of imagination!" Many devices are devoid of sonic character and personality, with manufacturers choosing in stead to focus on churning out endless cookie-cutter copies of previously suc cessful ideas.Therefore, equipment design that imbues the gear with creativity, innovation, and the personality of the de signer is especially valuable. Because of the unpredictable economics of this approach, however, most of the un usual, quirky, and interesting instruments and processors tend to come from smaller companies.Sherman Productions is one such company. A tiny Belgian concern employing fewer than a half dozen people, Sherman has come up with a unique and powerful filter box that has nothing to do with trendiness, offering instead a vast (and, frankly, dangerous) array of sounds.

	ON THE SURFACE

	The Filterbank is a 2U rack-mount, dual, multimode filter equipped with features such as an ADSR envelope gen erator, an LFO, MIDI control, and the ability to crossfade between lowpass, bandpass, and highpass filter modes. One immediately apparent and unusual aspect of the Filterbank is its enclo sure: a wedge with a sloping front panel.Rack ears are included in the form of mounting brackets with three sets of holes that allow the device to be mounted at three different angles. This makes the Filterbank easy to use in a conventional rack or dropped into a horizontal mount, with the controls facing directly upward.The Filterbank uses a typical wall wart AC adapter, so you'll have to make room on your power strips for yet an other one. This is unfortunate but un derstandable, given the cost of making versions with internal power supplies for different countries.



	FRONT VIEW

	The Filterbank has a fairly densely populated front panel (see Fig. 1). It's divid ed into three main sections-the bottom row contains the controls for each filter, and the top row has the glob al controls. The knobs are color coded: blue indicates a frequency knob, yellow knobs control the ADSR envelope generator, green indicates a volume con trol, orange denotes a resonance/power control, white is for balance knobs, and red indicates anti-controls (which I'll explain shortly).The Filterbank's controls for filters I and 2 are almost identical. Each filter has a frequency control (cutoff frequency for highpass and lowpass, center frequency for bandpass) and resonance control. Each filter also has a lowpass/bandpass/highpass balance knob, with which you can continuously vary the filter type.Now things get really interesting. Sherman recognized that the Filterbank's LP/BP/HP balance control alone would not permit a broad variety of filter types, so the company added an anti-phase-correction control for each filter. In its extreme counter clockwise position, this control adds the inverted output of the bandpass filter (-BP). In the extreme clockwise position, it adds the combined outputs of the lowpass and highpass filters (LP+HP). In-between positions give you a fraction of each output.This control has more uses than can be briefly described (see Fig. 2). You can use it to create a notch filter, an allpass filter, and an assortment of more com plex filters. A basic explanation of the math behind this control is included in the manual, but you need to work with it yourself to really understand.Filter 2 has only one control that filter 1 lacks: Harmonics. When synched to filter 1, filter 2's frequency is deter mined by that of filter 1. In this mode, the Harmonics rotary switch allows you to select from preset intervals between the two filters' frequencies. (For example, filter 2's cutoff frequency can be an octave below that of filter 1, a fifth below, and so on.) If you set the Harmonics knob to the Free setting, filter 2 will no longer be synched to filter I and will operate independently. (When the two filters are synched, filter 2's frequency control is inactive.)



	Controls that affect both filters in clude input level, frequency modula tion (FM) amount, ADSR envelope generator/envelope follower settings, LFO speed (frequency) and depth, am plitude modulation (AM) amount, and attack and release for the AR envelope generator. A toggle switch selects either ADSR or envelope-follower modulation. This circuit can be controlled by an external signal via the ADSR input jack, and it has a control-voltage output. When the circuit operates as an ADSR, the sus tain level can be continuously varied from positive to negative. Looking at the front panel, you'll no tice that three of the ADSR knobs (con trolling attack, sustain, and release) are aligned horizontally, while the third (decay) is higher up. When operating as an envelope follower, the control voltage output varies according to the amplitude envelope of the input sig nal. In this case, the S knob controls sensitivity rather than sustain, and the decay control has no function, which is why the D knob is not aligned with the others. Two more controls operate on both filters. The Bypass/Effects (Byp<>Eff) knob sets the wet-to-dry mix, which is straightforward enough. On the other hand, the Parallel/Serial (Par<>Ser) control, which smoothly crossfades be tween parallel and se rial routing of the two filters, has the poten tial for some very in teresting applications. When the Parallel/ Serial knob is all the way to the left (set to fully parallel), the input signal is fed independently to both filters, and the output of the filters is mixed and routed through the main output VCA. o (You can also take sep arate outputs from the two f ilters, rather than mix them.) When the Parallel/Serial knob is turned completely clockwise, to the serial position, you can route the signal first through filter I and then through filter 2. (The slope of each fil ter is 12 dB/octave, so two in series give you a 24 dB/octave slope where the filters overlap.) In-between Parallel/Serial settings route some of the signal in parallel and some serially, providing an amazing number of possibilities, especially in combination with the Resonance con trols. This control is noteworthy due to the flexibility that it provides and because it's not commonly found on this type of device.

	GETTING IN AND OUT



	In addition to the aforementioned ADSR trigger input and CV output, the rear panel includes a trigger input for the AR envelope generator; a 1/4-inch mono audio input; and 1/4-inch main and filter 1 outputs (see Fig. 3). The main and filter I outputs' functions depend on which one of them is connected and how the Parallel/Serial routing control is set (see Fig. 4). The Filterbank provides MIDI In and Out connectors and three MIDI Thru jacks. Also on the rear panel is the FM input signals coming through it modulate the frequencies of both fil ters. Plugging an external signal (which can be either audio or a DC voltage from an analog synth) into the FM input disables the Filterbank's onboard frequency modulation. Similarly, the rear- AM input accepts either DC voltage or audio in and modulates the Filterbank's VCAs, defeating the on board AM modulation. The Link In/Out jacks are an inter esting and smart feature of the Filterbank; they allow endless numbers of Filterbanks to be linked to create a single monster filter or an array of synchronized filters. These jacks carry a control voltage that, when multiple units are connected in series, allows the first Filterbank in the chain to con trol all filter Is in the successive units. Because only one Filterbank was pro vided for this review, we were not able to test the Link In/Out feature.



	SOUND PRACTICES

	Sonically, the Filterbank is an aggres sive, unwieldy monster. Depending on what you put through it and, most im portant, how you mix its signal in your music, the Filterbank can produce a staggering range of tones. They can sound dirty and harsh, lovely, or unlis tenable. You can create anything-from overblown extreme highs and lows with tons of distortion to smoother, more musical sounds with just the right amount of bite. The ADSR and LFO allow all manner of expressive (and often terrifying) effects, from huge sweeps to more percussive sounds. Once I realized that I was dealing with the sonic equivalent of weapons grade plutonium, I began to get a handle on how best to use the Filterbank In general, I found it most immediately appealing on drums and other rhythmic and percussive material. But its usefulness is by no means limited to this area: it can yield often amazing results on bass es, guitars, and miscellaneous samples. The main thing is to keep a tight control on its return level if you're using the Filterbank with a studio mixing console, because it can easily be overpowering. I found that limiting its returns worked well for dealing with this tendency. One noteworthy quirk in the review unit's sound was the presence of what seemed to be aliasing or clock noise in the output when the filters' cutoff frequencies were tuned way down. This sound reminded me a bit of the old PPG Wave synth; although some people might find the sound obtrusive, I think of it as a feature, not a problem. According to Sherman, the circuit design of the Filterbank has been altered slightly in the latest models, and one by-product of this change is the reuction of this artifact. I, for one, will miss it, but I'm sure some people will appreciate its removal. (Note that Sherman cannot update older units.) The Filterbank's input-level control is extremely sensitive, which is significant because the input-level setting has a lot to do with the character of the sound produced. There is a very fine line between "edgy" and "absurdly distorted" when setting this knob, and now and then it takes some tweaking to get things right. Also, there's a rather obvious but undeniably neces sary internal noise gate in the Filterbank; setting the input too low can cause this gate to react differently, which can lead to either interesting rhythmic effects or total frustration.

	MIDI CONTROL

	The Filterbank's MIDI implementation, although not exhaustive, provides control for many of the unit's pa rameters, including cutoff and reso nance for both filters; FM depth; VCA bias; attack, decay, and release controls for the ADSR envelope generator; and attack and release controls for the AR envelope generator. These parameters are handled by dedi cated MIDI Control Change messages. Creating onscreen faders for them in a sequencing program let me make inter esting automated parameter changes quickly and effortlessly. They all worked with impressive smoothness, even given MIDI's limited resolution. I wish the unit sent MIDI messages from all the front-panel knobs; this would make sequencing much easier and more comprehensive. However, incoming MIDI controllers are added to (and, for the timings, multiplied by) the values of the Filterbank's knob positions. This means that you can fiddle with a front- panel knob at the same time that a MIDI controller is varying the parameter. According to Sherman, sending out the knob position through MIDI would cause "stepping" and delay, and it would conflict with the unit's MIDI control. The best workaround would probably be to control the Filterbank parameters with a Peavey PC 1600, JLCooper Fadermaster, Keyfax Phat.Boy, or similar device and simultaneously record your moves in the sequencer.

	HOME-GROWN DOCUMENTATION

	Sherman's manual for the Filterbank is decidedly of the "home-grown" variety. Not since the Voyetra 8 synth have I seen documentation with such quaint freehand line drawings. Although haphazard in its look, layout, and organization, the manual does a fair job of explaining the unit's functions. (Particularly effective is Sherman's visual explanation of the differences between lowpass and highpass filtering.) In some cases, it explains a feature in terms of "set this, now try that," rather than explaining exactly what's going on, but you can figure things out well enough if you think about them for a while. Fortunately, the manual provides ample warnings about the Filterbank's potentially lethal aspects.



	TRUE GRIT

	Generally, I was impressed with the Filterbank. This thing is all character and hardedged personality. I loved the ability to do various tricks by cross-patching the rear external inputs and outputs. For instance, I could produce sub harmonic FM by connecting the main out to the FM input; many similar tricks are documented in the manual. In this respect, using the Filterbank is like working with a modular synth. I still wish the unit could send MIDI messages from all the front-panel knobs, although I recognize the difficulties in volved here. Also, a real power supply would be nice, particularly for reliabili ty in a live setting. These gripes aside, the Filterbank is a truly unique box that sounds like no other filter on earth. A quick note about the device's distribution situation is in order. Sher man is in the process of changing U.S. distributors. This should be resolved by the time you read this, but it is still up in the air as we go to press. If in doubt, you can check the Sherman Web site, or e-mail the company, or contact the Canadian distributor (see "Contact Sheet," p. 179). If you're doing adult contemporary, "cool" jazz, or (especially) religious music, do not buy this device. In fact, don't even look at it. Don't point at it. just walk quickly in the other direction and don't look back. However, if you need some extremely aggressive, colorful processing, get one now. Go on, just do it.



	Peter Freeman is a freelance bassist, synthe sist, and composer living in New York City. He has worked with such artists as John Cale, Jon Hassell, Chris Spedding, Nile Rodgers, Shawn Colvin, L. Shankar, Sus san Deihim, Richard Horowitz, and Seal.