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 ARP Quadra
Background The ARP Quadra is a fascinating synthesizer, a failed
attempt to create a leading edge polyphonic synthesizer, four analog synthesizers somehow grafted into one ugly duckling, yet it still has a certain charm and it is certainly has some unique sounds.
Launched in 1978, it was over shadowed by far more capable and fully programmable synthesizers from Roland and Sequential. Musicians soon hated it, as the poor build quality became all too
evident. Launched at a Prophet 5 price of over £2000, it proved uncompetitive and poor sales contributed to ARP's demise in May 1981.
Overview The concept of "many synths in a box" was created
after the Centaur polyphonic keyboard and guitar synth project was aborted in 1976. ARP fell back on existing designs with the Avatar based on the Odyssey, and the Quadra based on the
Omni. The Quadra has four sections: a bass synthesizer, a string synthesizer, a polyphonic synthesizer, and a two-voice, touch sensitive lead synthesizer.
All the analog designs are from previous ARP products, tied
together with new digital electronics. Full exploitation of microprocessor technology would have to wait for the Chroma project of 1981, the Quadra had to get to market quickly and ARP
chose to use of a microprocessor and preset memories was new, and stemmed from the newly available Intel 8048, the first 8-bit microprocessor.
20 years on the Quadra is gradually being accepted back into the
analog collectors acquisition list, thanks to a couple of sweet sounding LPF VCF's, an awesome voltage controlled 14-stage Phase Shifter (a Moog filter variation), plus strings and lead
sounds in one package. The Quadra does have some major weaknesses, such as the membrane controls, but its design idea of having the route between synth modules under microprocessor
control has often been mis-understood as poor programmability. ARP's marketing department didn't exactly help, as they tried to position the Quadra to compete with the Prophet 5.
Technical
The Quadra uses an early 8-bit 8048 microprocessor to control the routing between the synth modules and to scan the keyboard. It also stores the 16 presets into 128k bytes of memory using a 5101 CMOS SRAM chip.
Paul DeRocco, Joe Lemansky and Tim Gillette designed the phaser
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Product Spec
* 4x Analog Synthesizers 
* 1 VCO Bass
