The ARP is in very good condition, fully functional, recently refurbished by Boris Electronics, Chicago. A list of components and repairs are posted. The synth is in very good condition on the top, bottom, front and sides. The bottom has various scratches and the plate is not the original. One slider in the mixer section was partially broken off but still is high enough for editing and fully functional as all knobs and sliders.
The Quadra is pretty much a hybrid version of ARP's Omni II and Solus synths. It's a four-section synthesizer consisting of a Bass synth, Poly synth, Lead synth, and String synth. It is quite good at emulating each of these sounds and can function in any of its four modes at a time with the ability of layering the different sections! Sounds you create in any of the four sections are instantly recalled from memory by the push of a button! There are 16 program patches for storing your sounds. Other major features are the incredible phase shifter, tons of balanced audio outputs for each section, dual portamento controls and a superior arpeggiator...that's pretty good for 1978! On the downside, it has a fragile mylar front panel, very limited programability and a weird feature that autotunes the keys to play weird intervals.
The Bass synth section is monophonic and can be programmed to occupy the lower two octaves of the Quadra's 5-octave 61-note keyboard. The bass sounds pretty good and has 16' and 8' presets each for Electric and String Bass sections.