ARP QUADRA music synthesizer with flight case, circuit diagrams, manual and program chart. The ARP QUADRA music synthesizer represents an advanced generation of synthesizer technology from the late twentieth century, making extensive use of MSI and LSI scale electronics along with reasonably advance analogue op-amps.

The ARP Quadra was a 61 key analog synthesizer produced by ARP Instruments, Inc. from 1978 to 1981. The machine combined pre-existing products: the Omni II, Odyssey, a Solina-esque string synthesizer unit, a phaser and a divide-down organ with ADSR envelope, and a 4075 24 db low pass filter into one box. It had four sections: a Bass synth, Poly synth, Lead synth, and String synth. It was quite good at emulating each of these sounds and could function in any of its four modes at a time with the ability of layering the different sections.

Bass was on the bottom two octaves, and had two unison bass circuits (electric and string), with AR and a single pole low pass filter and a related AD envelope for cutoff. A string section was similar to the ARP Omni. Poly Synth, and a two voice Lead Synth similar to the Odyssey and a five-way mixer with four-unit outputs, a stereo pair, a line mono and an XLR out.

There were 16 program patches for storing sounds. Other major features include an incredible phase shifter, multiple balanced audio outputs for each section, dual portamento controls and a superior arpeggiator.

The 1970’s ARP Quadra synthesiser was used on countless disco records, funk, John Carpenter soundtracks, Genesis albums, soul, New Order records, Gary Numan’s Micro Music tour, Joe Zawinul. Jean Michel Jarre made great use of it. The list is almost endless.