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Arp2600

A late-production 2600, with the duophonic keyboard. Courtesy of Matrixsynth.

A semi-modular synth produced by ARP Instruments. It was ARP's second product to reach the market, after the 2500; it was first produced in 1970 and remained in production until ARP went under in 1981.

The 2600 was an analog synthesizer with three VCOs, a dedicated LFO, a lowpass VCF, a VCA, and two envelope generators -- an ADSR and an AR. It also contained a ring modulator, a spring reverb, and a noise generator with a built-in filter for varying responses. All signals were brought out to jacks on the panel, but a number of normalled connections reduced the need for patch cords. Oddly, the 2600 also contained a low-power amplifier and a pair of small built-in speakers. Techs and DIY'ers who add features often remove these and use the panel space for additional controls. Some 2600s have their electronics potted -- encapsulated in a resin-like material that makes servicing difficult. Performers and collectors interested in purchasing a 2600 are advised to find out if it has potted electronics before purchasing.

The 2600 underwent numerous design and engineering changes during its production run. Notably, the original monophonic keyboard was replaced with a duophonic keyboard having its own built-in LFO, a useful addition. Early production units had the keyboard built into the case, but ARP soon switched to a detachable keyboard which connected to the synth with a cable. The original VCF design (known by its part number, the 4012) was a clone of the Moog transistor ladder design; when Moog threatened a lawsuit, ARP replaced that with a different design (the 4072). However, a design error in the 4072 limited its cutoff frequency to about 2.5 KHz, resulting a dull sound. Techs have since discovered that changing a few resistors corrects the design error, restoring full spectrum response to the filter. See this page on Vintage Synth Explorer for a detailed rundown on the various production versions of the 2600.

Visually the earliest 2600s had white graphics on an electric-blue background. These are known as the "blue Marvins". Only a handful were produced in this configuration. The vast majority of 2600s produced had white graphics on a dark gray background. Early production units in this style are known as "gray meanies" because they have the potted electronics, which makes them very difficult to work on. Near the end of the production run, the panel was redesigned to use the orange-and-black color scheme (pictured above) which became the corporate standard in the late '70s. The production run continued until at least 1980, ending shortly before ARP declared bankruptcy in 1981.

Notable users of the 2600 include:

  • Tony Banks
  • Josef Zawinul of Weather Report
  • Jean Michel Jarre
  • Pete Townshend of The Who
  • Stevie Wonder
  • Edgar Winter, who had his 2600 modified with a longer keyboard cable. He then attached a guitar strap to the keyboard and wore it around his neck, keytar-style.

The 2600 sold surprisingly well for a relatively expensive synth, and is still highly regarded, so much so that several soft synth emulations of it have been created. Several well-known techs have developed modification packages which improve the sound quality (usually by replacing the low-performing 741 op amps used in most versions) and add new features such as a second VCA or a multimode filter.

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