Vintage 1970’s PAiA Electronics Model 2720 Analog Synthesizer

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via this auction

Note the button tab style keys.

"Built as a kit, it consists of 8 modules which could be connected with jumper cables to create an almost unlimited variety of different sounds. It has been stored for many years and with no way to test the unit (which requires an external amp and speakers) it is being sold for parts and repair.

Modules include:
Power Supply
Voltage Controlled Oscillator
Function Generator
Voltage Controlled Amplifier
Control Oscillator/Noise Generator
Voltage Controlled Filter – Band Pass
Voltage Controlled Filter – Low Pass
Keyboard Controller

Also included are booklets for assembly and operation of each module. Some of the booklets are stained but still readable. There are 6 single-wire and 4 coaxial jumper cables. The unit is about 32” long, 11.5” wide, and 6.5” high and is housed in a wood / metal case."