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DAVE SMITH INSTRUMENTS POLY EVOLVER KEYBOARD

Feb 1, 2006 12:00 PM, BY JASON SCOTT ALEXANDER

You can take the synthesis pioneer out of the hardware, but you can't take the hardware out of the pioneer — or something like that. For three decades, Dave Smith has advanced the electronic music industry with many great achievements, including his fundamental role in creating the MIDI protocol. In the mid 1970s, Smith designed the legendary Sequential Circuits Prophet 5, the first polyphonic and programmable microprocessor-based instrument. He continued with the groundbreaking Sequential Prophet VS (circa '86), which used a technique called vector synthesis to mix waveforms, and then the Korg Wavestation (circa '90), which took that concept further by creating a massive wave library of sampled sounds with a unique wave-sequencing and crossfading method for layering a number of these sounds.

Following many years of designing software synths (including Seer Systems Reality), Smith returned to his hardware roots. In 2002, he released the Evolver, a monophonic tabletop synth. Responding to pleas for a road-worthy, polyphonic version, he designed the Poly Evolver, essentially four Evolvers saddled into a 1U rack design. Its sparse front panel and tiny LCD sacrificed immediate tactile control. The Poly Evolver Keyboard (PEK) is the same basic instrument as the Poly Evolver rack but with a keyboard, lots of knobs, switches and other controls pleasantly laid out, with no menus to surf. Dave Smith Instruments' third time is definitely a charm.

AESTHETIC ATTACK

One glimpse tells you the PEK is a downright classy instrument. From the warm, purplish color and unique grain patterns of the Jarrah wood end-caps, to the intuitive and logical layout, impeccable fitting and sturdy assembly, the keyboard has the look and feel of an instant classic. With 77 endlessly rotating knobs, 59 red backlit switches, strobing blue LEDs and freaky, clear acrylic thumb-wheels backlit in blue, the instrument screams “tweak me!”

The knob-per-function spread, by and large, follows the subtractive-synthesis signal path left to right across the 61-note keyboard, which features velocity and aftertouch (pressure). The blue backlit 2× 16-character LCD and large, three-digit LED serve only to identify parameter values, program names and preset numbers; push a button or turn a control, and the selected parameter and value appear in the LCD. Aside from some global system-level commands, you'll rarely, if ever, need to view the display or maneuver through menus to edit the instrument. With a logical front panel like this, you may not need the editing software originally designed for the tabletop and rack Evolvers, but it's available for Mac/PC from the company's Website, should you so choose.

The back panel is loaded with unbalanced stereo audio jacks. Aside from the requisite main mix/audio out pairing, there are four separate sets of output jacks — one pair for each of the four voices within Evolver. When a plug is inserted into one of the separate outputs, that signal is disconnected from the mix output. This is particularly cool for sending voices to their own channels on your mixer for EQ, panning and processing. Another cool trick is to route the output of one voice to the external audio inputs. Then, in Combo mode, you can use one or more voices to process a different voice. Or, take two different voice outputs (programmed in mono) and run one to the left input and one to the right input for even wilder results. An obviously more conventional use of the audio inputs is to use the Poly as an external audio signal processor.

There's also a stereo headphone jack, ¼-inch jacks to receive sustain and two switch pedals/voltage control sources, MIDI In/Out/Thru ports and a dedicated Poly Chain MIDI Out port for linking up multiple Evolvers. Should you already own a Poly rack, for instance, you would hook the Poly Chain MIDI Out of the PEK to the Poly rack's MIDI In, and the main audio out of the PEK to the rack's special audio mix input to rig up an 8-voice system. Or, add a more affordable mono Evolver and expand the PEK to five voices for playing thicker chords. You can mix and match Evolvers in any combination.

MONSTER 4×4

A common thread when talking about the Poly Evolver is that everything happens at the voice level — atypical of most synths, which funnel all voices through a common sound-shaping path after the oscillator stage.

The basic PEK architecture is that it's four-voice, with four oscillators per voice. Oscillators 1 and 2 are analog and hardwired 100 percent left and right, respectively. The base oscillator frequency can be set over a 10-octave range, from 8 to 8k Hz, stepping in semitones. Waveshapes for these oscillators are sawtooth, triangle, sawtooth-triangle mix and pulse wave with voltage-controlled analog pulse-width modulation. Oscillator 2 can be set to hard sync to Oscillator 1, and glide can be set independently for each.

Oscillators 3 and 4 are digital (based on the Prophet VS), again hardwired left and right with the same frequency ranges. Waveshapes 1 through 95 are drawn directly from the ROM shapes within the Prophet VS, including a “blank” wave for achieving rests while sequencing. Waveshapes 96 through 128 are user-programmable via MIDI with the available software. Frequency modulation between Oscillators 3 and 4, including simultaneous bidirectional, can be applied, as can ring modulation.

The oscillators can be implemented in any combination (one analog and two digital, two analog and no digital, etc.). From here, signals travel slightly different paths. On the analog side of things, signals from oscillators 1 and 2 go through real analog voltage-controlled Curtis 2/4-pole resonant lowpass ADSR filters. There are two separate filters — one for the left channel and one for the right — for a true stereo signal path. From there, it's on to true analog voltage-controlled amplifiers (VCAs) with ADSR envelopes — again, one for each oscillator/channel.

Schematically, the analog goodness just described is actually embedded within an encompassing framework of digital interfacing and DSP. Alongside the analog oscillators are digital buses that carry not only the digital oscillators, but also a digital white-noise generator, A/D-converted signals from the external audio inputs and some other digital routings. These digital buses get preprocessed by the DSP, converted to analog and are then summed left and right with the analog oscillators on the analog buses. This allows you to treat digital oscillators with the analog lowpass filter and the VCA. From here, the whole shebang is A/D-converted back into digital, where all the craziness starts with highpass filters, distortion, delay lines and lots of feedback paths. Finally, everything goes back to analog for its journey out of the PEK.

If all that conversion scares you, don't let it. The two sets of stereo converters are running at a 48kHz sampling rate with 24 bits of precision for minimum impact on the analog sound. I could detect no detrimental effects, and in fact, the PEK is the fattest-sounding analog in my studio. The massive DSP assures that the PEK's analog tuning will be ultra-stable and not drift as with vintage machines. (If instability is your thing, however, then check out the cool oscillator Slop function.) Also, all internal controllers and DSP chips can be reprogrammed via MIDI, meaning easy feature additions down the road.

Á LA MODE

The Poly Evolver has two main modes: Program and Combo. Program mode sets all four voices to the same sound — one of the 512 presets (four banks of 128). Combo mode (384 Combos as three banks of 128) gives you complete flexibility over configuring the synth's four voices; you can stack or split the keyboard, layer sounds, assign different programs to different MIDI channels, set it to play multiple sequences synchronously and so on. There are up to four Parts in each Combo, though all four do not have to be used. For example, a split Combo, with one voice for bass on the low end of the keyboard and three polyphonic voices on the upper end, would only require two parts.

The Poly Evolver can also act as a complex stereo signal processor. In Combo mode, you can have one or more voices using the external signal input, so the external signal can be routed to all four voices with each voice doing different processing, such as filtering, envelope following, distortion, feedback, delay, driving a sequence, etc. What's freakin' cool is you can “play” a different effect per voice on the keyboard. Because the inputs can also be mixed in with oscillators, it provides a wicked way to process vocals, loops or other synths through the PEK for a monster MIDI stack that has the Poly Evolver sound.

It's worth emphasizing that each voice is physically its own synth; there are four discrete voice circuit boards inside. Essentially, as you play notes and consume voices, the demands are cascaded across the boards in a circular motion — evidenced by the “voice use” indicator on the front panel. When you press a fifth note, voice stealing is hardwired to the oldest note (for consistency, according to the manual). This all means that you can stack and create enormous lead sounds with up to 16 oscillators, or you can program up to four different sounds (all monophonic) and assemble them into a monster-sounding Combo.

SEQUENTIAL CIRCUITS

The Poly Evolver features a 4-track, analog-style step sequencer with 16 steps. Individual sequences can be routed to any standard modulation destination, and each step is a modulation source. Typical destinations would be parameters such as oscillator pitch, volume, pan and note duration. I also had a lot of fun programming tracks to step through the wave shapes of the digital oscillators; vary the pulse width of the analog oscillators; alter the amount of distortion, delay or tuned feedback with every step; and sprinkle poignant amounts of FM and ring mod to accent steps. The results are extremely dynamic and hair-raisingly cool.

The sequencer can be triggered from a variety of sources, including its own internal clock, by the keyboard, external MIDI step or with an external audio signal used to gate or advance the sequencer. Sequences can be routed to MIDI output destinations, including note number, velocity, mod wheel, pressure, breath and foot controller. Note values range from half-note to 64th-note triplets. There are tap tempo and variable sequence length, and you can even send the sequencer to modulate its own clock. Four identical LFOs can be unsynched or synched to the sequencer or MIDI tempo.

ANALOG HEAVEN

I was fortunate enough to play the PEK alongside the current crème de la crème of virtual analog (VA) synth: the Access Virus TI. (Look for the review next month.) Comparing the two is to compare apples to oranges, but having both helps to convey the strengths of a true analog sound over that of the best VA out there. It takes very little effort to make the PEK sound present and poignant in a mix. Dial up a single oscillator — analog or digital — noodle a bit with the lowpass filter, and you'll have something very attractive. Pairing true analog and with digital oscillators alone generates extremely fat results that VAs cannot match. What's really cool about the PEK's digital oscillators is that they become nice and trashy as the frequency increases, just like the original Prophet VS. Scanning their tables, you go from dark and creamy to sparkly and grating. It's all too easy to re-create vintage PPG wave moments.

Angst-filled musicians should love the PEK's tuned feedback and distortion effects. Tuned feedback employs two identical tuned delay lines — one for each channel of a voice. The pitch and amount of feedback can be controlled by any modulation source, including the sequencer. I was able to create the coolest plucked-string sounds by assigning the unit's third envelope to control noise. The real-time harmonic interaction between the base frequency of the main feedback loop and other factors, such as the filter frequency and number of poles, make any oscillator source slip into a nasty attitude. A Grunge parameter adds even nastier doses of screeching at higher levels of feedback looping. In a unique twist, distortion can be placed to only effect the external audio inputs or the internal sounds, as well. An Output Hack knob rudely destroys any sound.

You can accomplish a lot with PEK by experimenting, or by holding back, you can re-create classic, clean Prophet 5 warmth and early vector-synth atmospheres. Analog basses are enormous and superdeep; analog drums are ferocious; leads are solid and piercing; and strings are ridiculously lush, smooth and unlike anything a VA could ever pull off. Unleashing the instrument's wicked side, you can easily create some of the vilest ear-ripping sounds on Earth. As Smith himself says, with so many possible sources of gain along the synthesis path, it's easy to overload and corrupt a sound. Watch your overall output volume and the channel volume on your mixer to save your speakers.

You cannot achieve the same sounds on any other synth. With the delays, LFOs and step-sequencer at the voice level, insane and unique rhythmic possibilities abound. The wave sequence presets are extraordinary, and you can influence waveshape changes with further modulation (programmed or in real time) to the sequence destinations.

I did detect slight staircasing in the digital highpass filter, and I would have preferred sliders to knobs for some functions, including the ADSR envelopes. I consistently found myself longing for an extra two voices for playing two-handed chords. This is where the Poly Chain feature comes in handy, albeit at a pricey per-voice route. As PEK waveshapes have to be exactly 128 samples long, some sort of fixed-sample-size window that you could dial in and audition captured audio with a knob would be cool. It's a mystery to me why there's no digital output provisions.

FULLY EVOLVED

The PEK is a dream keyboard for both the player and sound designer. It combines the best of analog and digital, letting you do things you can't achieve anywhere else. While it can stay faithful to classic sounds we know and love, it definitely has a sound all its own. I can't stress enough the feeling of emancipation you get when sitting down to the PEK. All the traditional constraints found in not only virtual synths but also many hardware synths are lifted. Highly tweakable, complex and forever-evolving soundscapes are PEK's specialty, and the combo presets show this off wonderfully.

With far too many disposable products out there, a future classic like the PEK has been missing for a long while. The PEK may not do everything under the sun, but it's concise, approachable and accessible, and has enough function to allow deep exploration for a long, long time.