MATRIXSYNTH: Oberheim OB 8 with Midi & Aftertouch

Tuesday, June 14, 2016

Oberheim OB 8 with Midi & Aftertouch

via this auction

"Oberheim OB8 with factory midi in excellent functional and cosmetic condition.The OB 8 comes with a travel case and original OB8 operating manual and patch cassette.

This unit has been modified in 3 ways. 1) The original problematic Panasonic keyboard has been replaced with a new custom Fatar keyboard. This keyboard has a built in aftertouch sensor and was installed by Retrolinear. 2) A sophisticated AT circuit was installed by New England Analog and includes a Pyxis controller and external pressure pad controller. Check out YouTube videos by New England Analog and the Pyxis control system.The Pyxis controller allows the AT to control the VCO, VCF, VCA, and LFO by intensity and speed. A series of toggle switches on the back of the synth allow a variety of AT combinations such as pitch bending up, down, or Osc 1 up and Osc 2 down. Do a search on NEA's Pyxis controller and its capabilities and 3) bass boost which was done by replacing the 100k R505 and R506 resistors with 1M resistors(4) and building a network of 4x of 120K resistors and 0.0056 film caps in series and connecting the small network in parallel to the new 1M resistors.This modification helps create a better low end somewhere in between a standard OBX-A and an OB 8.

This particular unit was in great functional shape when purchased and I invested another $2500 with NEA and Retrolinear on the refurbishing and mods.The rebuild work done includes:
replaced capacitors in PSU
Repaired faulty envelope generator release control on upper four voices
Installed new 5V bridge rectifier
replaced 40109 chips and top voice board 3080 chips
Replaced calibration summing TL 071 Op amp and the two TL 072 output OP amps.
Installed Fatar keyboard with factory aftertouch sensor
Installed aftertouch circuitry and Pyxis AT controller and touch sensor pad
all 16 oscillators tuned and calibrated.
Loaded factory preset patches"

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