ARP Quadra

The ARP Quadra was a 61 key analog musical synthesizer produced by ARP Instruments, Inc. from 1978 to 1981. The machine combined pre-existing products: the Omni, Odyssey, a Solina-esque string unit, a phase shifter and a divide-down organ with ADSR, and a 4075 24 db low pass filter into one box. It has four sections. Bass is on the bottom two octaves, has 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 is 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 are 16 memory locations, but these do not provide storage of slider settings. The 8048 microcomputer and 128k of CMOS SRAM memory recalls 16 stored sets of on/off decisions about which waveforms and modulations are turned on in each of the four sections, and lead intervals. Using LEDs the player is visually directed to the sliders critical to the sound selected but their settings are not updated. This necessary tweaking and fine tuning is the weakness of the Quadra.