ARP Explorer (1981)

The ARP Explorer is the company's final synthesizer design. It came out in 1981, after ARP had already ceased operations. Dennis Colin, who had worked on the ARP Solus, conceived it as a more affordable and portable alternative to the ARP 2600 and Odyssey. It was also partly meant as an educational instrument. It is a string synthesizer, but with a full polyphonic voice per note: sixteen voices, each with its own VCO (sawtooth/square), a 24 dB/octave resonant low-pass filter with ADSR, and its own VCA. The keyboard has 49 semi-weighted keys (C to C) and includes aftertouch, which adds a lot of expression. The implementation is unique, though, and not compatible with most modern MIDI controllers.

The front panel is laid out in sections: Strings (with vibrato speed choices), Ensemble, Organ, Bass, and Synth. There are separate volume controls for master, bass, and ensemble. The filter section has cutoff, resonance, and a full ADSR envelope. The LFO produces sine, saw, and stepped noise waveforms, with rate and delay controls. There are two pitch slides for the VCO. Input/output includes CV/Gate out (buffered), a headphone jack, a ¼" audio output, a sustain footswitch input, and CV/Gate in. There is no patch memory. The instrument measures 30" × 3" × 10" and weighs 18 lbs. That is large and extremely heavy for its size, and the design looks odd.

The model name causes some confusion. Some sources conflate the two names, but the consensus among owners points to the Explorer I as the budget variant.

ARP's advertising in the mid-1970s, for the Odyssey, Pro Soloist, and Axxe, called the company "the world's leading manufacturer of electronic music synthesizers" (Modern-Recording, April 1976, p.43). By the time the Explorer reached the market, the company was already gone. What little reception exists comes from owner accounts decades later, and opinions are mixed. The string section is often called the weak point - acceptable but not remarkable. The synth section is described as very raw and big-sounding, and the bass as thunderous. Aftertouch is widely praised for adding real expressive range. The common verdict is that it's not a great synth, but a very cool and unique one that can deliver unusual sounds.

Surviving examples are rare. A 2023 Reverb listing in excellent condition asked $1,850. Known issues include a power supply that tends to fail (no longer manufactured), leaking capacitors, noisy sliders and switches, and an aftertouch membrane that is no longer available. Those who maintain these units recommend replacing the power supply and capacitors before they fail.

Known Specifications

• Polyphony: 16 voices (one VCO/amp/VCF envelope per voice)
• Oscillators: 1 VCO per voice (sawtooth / square)
• Filter: 24 dB/octave resonant low-pass with ADSR
• Envelopes: AR (ensemble), ADSR (filter and VCA)
• LFO: Sine, saw, stepped noise; rate and delay controls
• Keyboard: 49 keys (C–C), semi-weighted, with aftertouch
• Memory: None (no patch storage)
• Controls: Volume (master, bass, ensemble); filter cutoff, resonance, ADSR; LFO rate, delay, waveform select; VCO pitch slides; section switches (strings/ensemble/organ/bass/synth)
• Input/Output: CV/Gate out, headphones (¼"), audio out (¼"), footswitch (sustain), CV/Gate in
• Dimensions (W×H×D): 30" × 3" × 10"
• Weight: 18 lbs
• Production years: 1981 (introduced after ARP ceased operations)
• Designer: Dennis Colin

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