ARP Odyssey Mk II (1975–1978)

That snarling, buzzing, duophonic beast with the gold lettering and a filter that once made Moog lawyers twitch.

Overview

Plug in a Mk II ARP Odyssey, flip the power switch, and a low growl comes out of the power supply. It isn't the warm, round purr of a Minimoog. It's sharper and more aggressive. The black-and-gold front panel is brushed aluminum with crisp silk-screening, and it looks like it was built for a studio in 1976. The Mk II shares DNA with the earlier white-faced Mk I, but this is where ARP got serious about reliability, serviceability, and a Moog-like filter tone - without actually being Moog.

Produced from 1975 to 1978, the Mk II (models 2810-2815) was ARP's answer to evolving market demands and their own internal refinements. It kept the same 37-note duophonic keyboard and dual-VCO architecture, but nearly everything under the hood got an upgrade. The oscillators got better tracking, the power supply was beefed up, and the keyboard circuitry was redesigned to support CV/Gate control as standard, no factory mod required. That makes the Mk II the first Odyssey you can sync to a drum machine or modular rig from the era without jumping through hoops.

The real story is the filter. Early Mk IIs (like the 2810) still carried the original 2-pole 4023 filter - light, bright, a little thin by modern standards. By mid-1976, ARP swapped it out for the 4035, a 4-pole ladder filter that bore an uncomfortable resemblance to Moog's legendary design. Rumors swirled about lawsuits, but the truth is ARP paid a quiet licensing fee and moved on. The 4035 gave the Mk II a thicker, more resonant low end and a self-oscillating character that could go from a smooth sine wave to a screaming harmonic edge. It was built to cut through live mixes and analog tape hiss alike.

Later in the production run, ARP replaced the 4035 with their own 4075 filter, which became standard across the Mk II and III. It was more stable, but it had a known bandwidth limitation - it rolled off hard above 12-14 kHz, especially at high resonance. That makes the rare early Mk IIs with the 4035 the holy grail for collectors, and they command premium prices. If you find one, check the filter board carefully. Some were retrofitted.

Then there's the duophony. Call it "paraphonic" if you want, but the Odyssey's keyboard scanning system assigned one oscillator to the highest note and one to the lowest, and that was revolutionary in 1975. You could play fifths, octaves, even simple chords with real analog weight, not just stacked monophony. It isn't polyphony, but it's expressive, and Herbie Hancock and Jean-Michel Jarre used it as a compositional tool.

Specifications

Manufacturer	ARP Instruments, Inc.
Production Years	1975–1978
Original Price	$1,695
Polyphony	Duophonic (1 or 2 notes)
Oscillators	2 VCOs with sawtooth, square, pulse, PWM, oscillator sync, ring mod
Filter Type	4-pole VCF (4035 or 4075), 2-pole high-pass filter
Envelope Generators	ADSR and AR (switchable per function)
LFO	Sine, square, sample & hold
Noise Source	White and pink noise
Keyboard	37 keys, duophonic scanning
Pitch Control	Rotary knob (early), PPC buttons (late)
CV/Gate	CV In/Out, Gate In/Out, Trigger In/Out
Outputs	High (RCA), Low (1/4"), External Audio In
Inputs	Portamento footswitch, pedal (VCO2 pitch, filter cutoff)
MIDI	None
Weight	24 lbs (10.9 kg)
Dimensions	34.5" x 13" x 5.5" (87.6 x 33 x 14 cm)
Power	115V AC, 60 Hz (internal power supply)

Key Features

The 4035 Filter: Moog’s Shadow

The 4035 filter is why some people lose sleep over Mk II Odysseys. It's a 24dB/octave ladder design that behaves almost identically to Moog's 904A - warm, punchy, and capable of self-oscillation that's musical rather than brittle. Cranked, it growls, which suits basslines that need to fight through a mix. ARP adapted the design rather than copying it. The resonance is slightly more aggressive, and when driven hard it adds a subtle grit that Moog's smoother design lacks. The catch is that these early 4035-equipped units are rare. Most Mk IIs rolled off the line with the later 4075 filter, which is stable but lacks the high-frequency extension and harmonic richness of the 4035. If you're hunting for a Mk II, serial number and filter board inspection are mandatory. A 2810 or early 2813 with the 4035 is a different instrument, and worth the premium.

Duophony Done Right

The Odyssey wasn't the first synth with duophony, but it was the first to make it practical. The keyboard scanning system assigns VCO1 to the highest note played and VCO2 to the lowest. There's no voice allocation menu and no firmware, just analog logic that responds in real time. You can play a fifth, bend the top note, and the bottom stays locked. It's expressive and immediate. It isn't foolproof, though. Play three notes and the synth picks the top and bottom, dropping the middle. You can treat that as a feature, an analog arpeggiator with attitude, but it's not polyphony. And if you're used to modern synths, the lack of velocity or aftertouch will feel limiting.

Proportional Pitch Control: Ahead of Its Time

Late Mk IIs began shipping with ARP's Proportional Pitch Controller (PPC), three pressure-sensitive buttons for pitch bend up, bend down, and vibrato. It was a bold move away from the rotary knob of the Mk I. Some players miss the smooth sweep of the knob, but the PPC offers more nuanced control. Press lightly for a subtle wobble, hard for a full-tone bend. Not all Mk IIs have it. Early models kept the knob, and some were retrofitted, so know which version you're getting. The PPC is a signature of the later Mk II and Mk III, and it's one of the reasons the Korg reissue included switchable behavior.

Historical Context

The Mk II arrived at a turning point. The Minimoog had proven that compact, performance-ready synths could sell, and ARP needed to evolve. The original white-faced Odyssey (Mk I) was brilliant but finicky - hard to calibrate, prone to drift, and lacking standard CV/Gate. The Mk II fixed that, and it was a refinement of the entire platform, not a cosmetic refresh. The black-and-gold scheme also matched the look of ARP's other pro gear, like the 2600 and Omni.

At the same time, ARP was under pressure. Japanese synths like the Roland SH-3 and Korg 700 were undercutting them on price. The Odyssey had to be more reliable, easier to service, and more gig-ready, and the Mk II delivered. It became a staple in progressive rock, jazz fusion, and early electronic pop, and it was heard on records by ABBA, Ultravox, and Herbie Hancock. It was a different flavor of analog from the Minimoog - brighter, edgier, more experimental. The later Mk III would get a sturdier chassis and XLR outputs.

Collectibility & Value

The Mk II splits the vintage synth world. Some swear by the 4035 filter and will pay $5,000+ for a clean 2810. Others see the 4075-equipped models as more stable and practical, trading high-end sizzle for reliability. Either way, condition is everything. These synths are 45+ years old, and the weak points are well known.

Tantalum capacitors are the biggest threat. They degrade over time, can leak, and when they fail, they take op-amps and power supplies with them. Any Mk II that hasn't been recapped, especially the power supply and filter board, is a ticking time bomb. Replacing them with modern electrolytics is standard practice and expected at this age.

The original sliders are another issue. They wear out, get scratchy, and can introduce noise. Some owners retrofit LED sliders for smoother operation and visual feedback. Synthchaser's upgrade is popular, but purists prefer original faders. Keys are generally sturdy, but bushings dry out, and contact cleaning is often needed after decades of use.

Serviced, stable Mk IIs with the 4075 filter sell for $2,800-$3,800 depending on cosmetics. A verified 4035-equipped unit in good condition can fetch $4,500-$6,000. Fully restored examples with LED sliders, recalibrated oscillators, and upgraded power supplies command even more.

Before buying, find out whether it has been recapped, whether the oscillators are stable, whether the filter self-oscillates cleanly, and whether the keyboard is responsive. Also find out which filter it has. Don't trust the model number alone; open it up or get a service report. This isn't a synth to buy blind.