Modded ARP 2600 analog synthesizer

via this auction

"ARP 2600 synthesizer with ARP 3604P keyboard (serial #'s 26888 & 36888, respectively). Restored & customized with really useful upgrades by Tim Smith of Weyer-Smith Labs/The Audio Clinic in 1995. Do a Web search for "ARP 2600" for various descriptions of this popular analog synthesizer. The ARP 2600 was used by a wide variety of artists including Genesis (Tony Banks), Edgar Winter (on "Frankenstein"), Weather Report (Joe Zawinul), The Tubes (Michael Cotton) and many others.

After restoration, this unit sounded incredible. Upgrades, customizations & repairs included (see photos):
• replaced VCF wih 4072 filter (22kHz response), and added VCF input coupling modification to eliminated 'thumping' sound defect
• added +1/-1 octave switches for each VCO, and Multiples jacks
• added 4 mode envelope time extension modification for both ADSR & AR envelopes (X1-X5 modes)
• did "2600/3604/Oberheim" modification (CV1=standard; CV2=2nd voice)

• added 1/4" output jacks (above standard mini-jacks)
• modified reverb system for better response and 14 dB less noise
• added saw/square-wave form switches to each oscillator to eliminator patch cords for this common patch
• installed standard (IEC-type) power cable interface
• replaced op-amps with BurrBrown AP2604 audiophile components, and in voltage processor section to fix Lag offset tuning problems
• replaced keyboard interface cable and cleaned jacks & plugs, and repaired, calibrated, timed & tested keyboard

• rescaled & cleaned power supply, pots., sliders, etc., and replaced defective sliders"

Update: As always be sure to read auction descriptions on eBay in full. This one is being sold "As Is" and appears to have some issues. Thanks to sun butler in the comments for calling this out.