Earlier this year (Remix, February 2006), the Dave Smith Instruments Poly Evolver Keyboard (PEK) was cited as possibly being the best analog-synth design

Earlier this year (Remix, February 2006), the Dave Smith Instruments Poly Evolver Keyboard (PEK) was cited as possibly being the best analog-synth design ever. With the release of the monophonic Evolver Keyboard version, Dave Smith Instruments' (DSI) latest ad declares the Evolvers to be “21st Century Prophets,” modern versions of the classic Sequential Circuits Prophet-5 and Pro-One, which were also Dave's creations. What the ad doesn't mention, though, is the remarkable digital influence of the Prophet VS and advanced 4-track step sequencer that together make the Evolver Keyboard much more than a mere analog bass or lead synth.

Although the familiar electric-purple and blue Evolver Keyboard (EK) is only 26-by-12-by-3 inches — and extremely portable at about 13 pounds — it feels anything but diminutive to touch and play. Comfortably spaced controls — 58 endless-turn knobs and 35 switches — span the three-octave, Velocity- and pressure-sensitive, fast-action keyboard. This true knob-per-function spread intuitively follows the subtractive synthesis signal path from left to right, with the 16-by-2-character blue backlit LCD serving only to identify parameter values and program names.

The EK saves space by doubling the duty of two rows of filter- and amp-section knobs to also control the step sequencers. Around back, unbalanced stereo outputs join headphones out, two ¼-inch Pedal/CV jacks, MIDI In/Out/Thru and a special Poly Chain MIDI Out port for linking multiple Evolvers. To expand on the EK's single voice, you can connect this output to the MIDI In of any other Evolver model (original desktop monophonic, 4-note rack, 4-note PEK or another mono EK) for a potentially endless cascade of polyphony. Stereo audio inputs allow you to route external signals for envelope following and processing using the EK's entire set of voice parameters.


The EK's synth structure starts with two true-analog oscillators and dual independent digital oscillators sporting the same 128-wave library as found in the Prophet VS. Analog Oscillators 1 and 2 are hardwired 100-percent left and right, respectively, and offer saw, triangle, saw-triangle mix and pulse wave with voltage-controlled PWM. Oscillator 2 can hard sync to Oscillator 1, and glide can be set independently for each analog oscillator. Frequency modulation can be applied between digital Oscillators 3 and 4, including simultaneous bidirectional and Ring (amplitude) modulation.

Although tightly integrated, the analog and digital sides of Evolver's voice do travel slightly different paths. Analog oscillators 1 and 2 go through the same real analog voltage-controlled Curtis 2/4-pole resonant lowpass ADSR filters as in the Prophet 5, with a separate filter on each channel for a true stereo path. Digital oscillators 3 and 4, a white-noise generator and external input signals travel down a common digital bus that gets D/A converted and summed with the analog oscillators; that allows the digital signal components to enjoy the same lowpass-filter treatment as the analog. 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 that interact with the analog section. The DSP provides exact tuning for the analog oscillators, but you can use the oscillator “Slop” function if drift is your thing.

The sequencer can generate four separate sequences, each as many as 16 steps. These can be routed to any voice parameter or standard modulation destination, and each step is itself a modulation source. Aside from typical destination types (oscillator pitch, filter cutoff, etc.), I like programming EK tracks to step through digital oscillator wave shapes for pseudo-wavesequencing — an effect showcased throughout the EK's four factory banks (128 presets each, for a total of 512 memory locations). The sequencer can trigger in a variety of ways: via its own internal clock, keyboard, MIDI step or with an external audio signal used to gate or advance the sequencer.

Modulation is definitely EK's strong suit. Four LFOs carry ranges of 30 seconds (slowest) to 261 Hz (fastest) — middle C — during free operation. When synced to the step sequencer or MIDI, the range can be anywhere from 16 cycles per step to one LFO cycle taking 32 steps. There are also four discrete Modulator slots providing ways to send any predefined mod source (such as a sequence or LFO) to even more destinations, with different amounts; there are some truly off-the-wall mod sources, such as noise and digital oscillators, allowing for craziness such as audio-rate modulation.


The immediate control and spontaneity in sound design make the EK mind-blowing to play. Pairing the analog and classically sourced digital oscillators with those gorgeous filters alone creates a density and authority you won't begin to find in modeled synths. To really cut through a tough mix, try the Tuned Feedback — essentially two identical delay lines, one for each channel. There's also Grunge, which adds nasty doses of screeching at higher levels of feedback; three independent stereo tap delays; distortion; and Output Hack, which rudely decimates any sound.

The Evolver Keyboard goes well beyond the old analog stuff in power and flexibility, combining obese old-school warmth with unbelievable signal routing and adventurous processing/gain architecture. Once again, it gets the highest praise.



Pros: Same jaw-dropping aggressive sound as its polyphonic big brother. Dual true-analog plus dual Prophet VS — style digital wavetable oscillators. True stereo path with the same Curtis filters as original Prophet-5. Retro 4-part 16-step sequencer. Knob-per-function means no menu surfing. Highly portable. Ridiculously fun to play.

Cons: Wall-wart power supply and cable is rather short. No digital I/O.