ARP 2500 Preset Voltages (c. 1970)

A ghost in the ARP 2500’s architecture — a module promised but never mass-produced, designed to unlock preset control voltages on a system that otherwise demanded total patching commitment.

Overview

An ARP 2500 is not a casual instrument. Every sound comes from oscillators, filters and envelopes wired together through switches instead of patch cables. Each new sound is a new puzzle. ARP knew that had limits. The 1026 Preset Voltages module was meant to give the 2500 a kind of memory: selectable, manually triggered control voltage banks that could recall tuning, filter or modulation states without rewiring the system. The design was simple. Two channels of eight preset voltages, each level set by a front-panel pot, each step activated by a button or an external gate. You could flip between sounds the way you change channels on a radio.

You won't find one in most surviving systems, because the 1026 never made it past prototype. It was announced in ARP's August 1970 Tonus catalog at $285, as part of a group of "lost modules" - utility and control expansions that ARP teased but never released at scale. Only a handful of full-sized replicas surfaced decades later. Enthusiasts built them from fragments of documentation and reverse-engineered the logic from related modules like the 1050 Mix Sequencer and 1027 Clocked Sequential Control. The original design used 3mm LEDs for step indication, in an era still clinging to incandescent bulbs, and relied on CMOS logic for gating and sequencing. It was meant to connect to the 1027 with an RS232-style cable at the rear, acting as an expander that could drive multiple parameter banks in sync with the sequencer.

The 2500's switch matrix was brilliant in concept, but it made real-time performance nearly impossible. You couldn't save a patch. You couldn't recall a sound. You couldn't flip to a second timbre without breaking half a dozen connections. The 1026 was ARP's answer, a bridge between the purist modular ideal and the need for performance flexibility. Pete Townshend, one of the few rock musicians to own a full 2500, once bragged that his system could access "20 sets of preset control voltages." That was likely achieved through custom modifications or early prototypes of modules like the 1026. Jean-Michel Jarre, another 2500 user, leaned into the machine's complexity and used it to build evolving textures rather than quick changes. For everyone else, the lack of preset voltage control stayed a glaring omission.

Specifications

Key Features

A Module That Never Was — But Should Have Been

The 1026 was more than another utility module. The ARP 2500 was built on the premise that every connection should be deliberate, and that synthesis was a hands-on act of creation, not recall. The 1026 went against that a little, giving both immediacy and complexity. With two independent channels of eight voltage presets each, it could store tuning offsets for a multi-oscillator stack, or set filter resonance points for a performance sequence. The selectable 2V and 10V output ranges meant it could drive anything from oscillator pitch to VCA gain. And the sync with the 1027 sequencer via rear cabling meant it could change along with a patch, not just jump between static states.

Front-Panel Control Meets Modular Discipline

Unlike later digital preset systems, the 1026 kept the modular approach. You still set each voltage by hand, turning tiny front-panel pots to the level you wanted. There was no LCD, no menu, no MIDI. Once set, you could trigger those voltages on demand, either with one of the eight momentary switches or with a gate from the sequencer. The LEDs gave immediate feedback in a system where most signal flow was invisible. XOR logic (as implemented in later Eurorack recreations) allowed only one step to be active at a time. That prevented accidental overlaps that could send a VCO screaming or a filter into self-oscillation.

Integration Through the Backplane

The rear-panel connector linked the 1026 to the 1027 Clocked Sequential Control, which made it part of a larger sequence. That allowed parameter changes to follow note progression. A bassline could shift its filter cutoff every four steps, or a lead could spike resonance on the offbeat. The 1026 would be slaved to the same clock that drove the notes. Because it used the same switch matrix as the rest of the 2500, its outputs could be routed to any bus, which gave it access to the whole signal path.

Historical Context

The late 1960s and early 1970s were a battleground of philosophies in synth design. Moog leaned into patch cables and musical intuition. Buchla embraced abstraction and touch plates. ARP, founded by former NASA engineer Alan R. Pearlman, took a more clinical approach built on precision, stability and voltage control. The 2500 was ARP's flagship, a system built for studios and institutions, not stage performers. It appeared in the 1977 film *Close Encounters of the Third Kind*. But it resisted easy use. There were no presets and no memory. You built a sound, recorded it, and tore it down to start again.

The 1026 was ARP's attempt to fix that. It was announced around 1970 alongside other unreleased modules like the 1035 Triple Modulator and 1046 Quad Envelope Generator, as part of a plan to expand the 2500 beyond its core architecture. But ARP was a small company, and the 2600, a more affordable and portable synth, soon took priority. The 2500 remained a boutique instrument, with only about 100 units ever built, each customized to the buyer's needs. The 1026 never reached production, whether due to cost, complexity or shifting focus. It survives as a footnote in catalogs.

The idea of preset control voltages lived on in later synths, from the Oberheim 4-Voice to the Sequential Circuits Prophet-5. Even the 2500's own 1050 Mix Sequencer offered some preset functionality, mixing audio and gate signals across multiple channels. But the 1026 was pure control, a way to automate the invisible parameters that shape sound.

Collectibility & Value

You can't buy an original ARP 1026 Preset Voltages module, unless you find a one-off prototype or a hand-built replica from the 2010s. No production run ever happened, so there's no market value in the traditional sense. The concept has gained cult status among ARP collectors and Eurorack enthusiasts, though. In 2024, AMSynths released a Eurorack version, the AM1026, as part of their "lost modules" project, selling for around $395. These modern recreations are faithful in function, with the same dual-channel, 8-step design, selectable voltage ranges and manual/external triggering. They're sought after by ARP 2500 system owners using Behringer's 2500 reissues or modular clones.

For vintage 2500 owners, the missing 1026 is a known gap. Some have built custom solutions using multiple S&H modules or external sequencers to simulate preset voltage banks. Others use the 1050 Mix Sequencer to switch between control states, though it's not a direct replacement. If an original 1026 ever surfaces, say in the estate of a former ARP engineer or a long-lost studio, it would instantly become one of the rarest and most valuable ARP artifacts.

Buying advice? Don't look for one. If you're restoring or expanding a 2500 system, consider the AMSynths Eurorack version or a similar modern solution. They won't match the original aesthetics, but they restore a missing piece of the 2500's intended functionality. If you find documentation or schematics from an early prototype, you're holding something closer to synth archaeology than gear.

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