MATRIXSYNTH: Vintage ARP Quadra Overhauled by Synthchaser

Thursday, October 03, 2019

Vintage ARP Quadra Overhauled by Synthchaser

Uploaded on Oct 3, 2019 Synth Chaser

via this auction

"This ARP Quadra has just been fully serviced & overhauled by Synthchaser, the west coast's leading ARP specialist - recapped, new key bushings, new touch sensor, sliders disassembled, cleaned and refurbished, clean, fully functional, calibrated, in tune and sounding great. This synth was the final masterpiece of ARP Instruments and added a powerful 2 oscillator lead synthesizer to the bass, poly strings, and poly synth already found in the ARP Omni 2. Add in the lush 14 stage voltage controlled analog phase shifter, a sequencer (more like arpeggiator), assignable aftertouch, 61 key keyboard, and package it all into the coolest looking synth design ever and you have an ARP Quadra!

This synthesizer has just (October 2019) been refurbished by Synthchaser. This is not a lame "tweak a couple of trimmers" service. The synthesizer was torn down to the bare chassis, totally refurbished, rebuilt, and completely calibrated. Work included:

Power supply rebuilt - All tantalum and electrolytic capacitors in the power supply have been replaced, and high quality, high temperature 105 deg C capacitors have been used for the power supply filter capacitors.

All polarized capacitors replaced - The tantalum capacitors in ARP synths are ticking time bombs, and 40 year old electrolytic capacitors are past their prime. All of the 150+ tantalum and electrolytic capacitors in this synth have been replaced with new electrolytics to help provide stable operation for years to come.

4075 Filter Enhancement - The ARP Quadra uses the same 4075 filter submodules found in the Odyssey, Omni, Avatar, and Pro DGX which was designed with a calculation error that limited the cutoff frequency. Both of the 4075 filter submodules (for the lead synth and the poly synth) have been recapped, and corrected to provide superior frequency response, and tested for proper operation in the Synthchaser custom test fixture.

Sliders replaced and refurbished - The 6 sliders in the mixer section of the keyboard have been replaced with new sliders. The remaining 29 sliders for which no replacements are being manufactured have been removed, ultrasonically cleaned, received new 3D printed slider shafts, and lubricated. All sliders have original ARP slider caps.

New aftertouch sensor - The original aftertouch sensors are a common failure point-- the aftertouch sensor has been replaced with a new long-lasting one to ensure the aftertouch will work for years to come

Many new parts - Many parts have been replaced including tempcos, IC chips, battery holder, and the CPU chip.

Keyboard rebuild - New key bushings installed, keys removed and ultrasonically cleaned, buss bar and key contacts cleaned and adjusted

Oscilloscope calibration - Fully calibrated to factory spec using oscilloscope and frequency counter."

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