“ARP 2600 ARP 2600 This is an ARP 2600 Synthesizer. However the setup shown here is not exactly typical, and those who know the synthesizer will recognize the importance of these features. The synthesizer itself is a Rev.2, while the keyboard is a Rev.4 3620 two-voice model. Definitely Not an “off the floor setup, but here’s why this is significant. When the Rev.2 versions were built after a redesign of the original and problematic Rev.1 “blue meanie” 2600’s, they still utilized the Arp’s original 4012 VCF design, which was a copy more or less , of Bob Moog’s transistor ladder lowpass VCF. Eventually, Moog and ARP went to court over this, and the Rev.3 & Rev.4 used the not so awesome 4072 VCF. At the time of the Rev.2 there was no such animal as the two-voice 3620 keyboards, you had the simpler 3604 and the really simple 3601. It wasn’t until some years that ARP came up with the 3620, which also provides an LFO, some pedal controls and a few other interesting features. The one here is from the final 2600 revision, Rev.4, as noted by the orange graphics and the ‘no-logo’ ARP logo. The Synth here also, has its distinctive rectangular ‘Tonus Logo’, as opposed to Rev.3 with the ‘G-clef’. The S/N tag on the side also says “Manufactured by Tonus. As would be expected on a 50 + year old piece of gear, the cosmetics are not the most perfect. There’s some typical tolex snags and scratches, a small issue with the corner of the wooden housing, shown in pictures, and a little oxidation on the case metal. Electronically, however, the unit is perfect, with VCO 3 having been replaced with a breadboarded copy in 2007, and VCO 1 having had that done around 1994. Slider caps are missing here and there, but only one not-too-essential speaker slider has taken a hit. The synth sadly has a couple of major bits missing, the handle on top, not that you would carry it by that anyway. And also there was no front lid when I acquired it. The 3620 keyboard is a later vintage by perhaps 7-8 years, and accordingly is in great shape. It’s complete and works great. Both it and the synthesizer were fully realigned and calibrated when the VCO was replaced in 2007, and they’re working magnificently. If you want a 2600 that offers everything that the legendary synth could have in store, this is the one you need! It comes with owners manual, original power cords and the service manuals for both the synthesizer and the 3620 keyboard with great illustrations that can give an additional understanding of this synthesizer. ” Click here to visit listing on eBay
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ARP 2600 with ARP 3620 Keyboard
“Beautiful Arp 2600 that has been in storage for a long, long time. It is intact-all slider caps are in place as you can see as well as all jacks and switches. There were some professional modifications done by the previous owner (switches/jacks at ADSR and switches on 3620 kybd, and a pot above the kybd CV in the filter section- see pics). I never took the time to determine what the mods did, but you can surmise. I turned it on about 2 months ago, and all three oscillators were working, however after literally sitting for years (it has been more than a decade), it’s going to need a thorough going over by a specialist. If I were the buyer, that would be the first on the list- have it completely gone through, cleaned and brought to spec. If you’re gonna invest in one of these, this one is worthy of your consideration mainly because it’s a very clean unit (no signs of any physical or psychological abuse)! ” 
“ALL GEAR IS TESTED AND GUARANTEED TO BE 100%
“ARP 2600 model 3620 keyboard by itself, with two foot switch pedals (modified aftermarket).
“Arp 2600 semi-modular synthesizer with 3620 keyboard
“Rare opportunity
“Recently found in storage where it’s been for over 15 years. In very good cosmetic condition, but will need to be refurbished. As the title says, this is the more desirable 3620 with a dedicated LFO. ” 
“Recently (about a month ago) refurbished by one of the best techs in SoCal (Montoya). It was also previously professionally maintained when I lived up north, about 4 years ago (Siegenthaler). Many 2600s are electronically flaky, and most of any of the keyboards are internally a wreck — but not this pairing. They are electronically in excellent shape, and also are in fairly good shape cosmetically.”
“This vintage ARP is being sold for parts/repair. It does power on (you’ll need a Belkin 17952 power cable available for $20 on eBay) but is being sold as is untested and intended to be sold to someone who would like a great opportunity to buy one of these at a cheaper price for restoration or re-sale purposes. ARP itself is in nice condition shape just missing a few faders the keyboard is in rougher condition and may need more work than the ARP itself.” 
“Arp 2601 Synthesizer in overall fair-to-good used condition.
” Classic vintage Arp 2600 analog semi-modular synthesizer with model 3620 keyboard in absolute museum quality condition. This synth was in climate controlled storage, and unused for over 25 years of its life. It has just had a complete refurbishing and had it’s op amps upgraded by RetroLinear, and is absolutely 100% guaranteed to be in perfect operational condition. As you can see from the pictures, this synth is in immaculate cosmetic condition, with only the most minor of rub marks on the case. It’s never been on tour, or used for any live performance. It even smells new! You won’t find a cleaner or more perfectly functioning 2600 anywhere.
“Super-rare vintage ARP 2600 Semi-Modular Analogue SynthesiSer with matching serial Duo-phonic 3620 silver livery.
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” Rare Arp 2601 Synthesizer. It’s time for it to be used to create music again! For many years, it was stored in a spare bedroom closet, and for years, I was going to have it restored and brought up to spec, but alas…, I ran out of time and interest… I did plug it in and turn it on… and all three oscillators generated tone, and they seemed fairly steady (no severe audible drift when tuned to A440 while on). However, I did not go through and test all of the functions and/or all the other modules.
“Stunning original condition and superb working order. Complete professional service completed in February 2018 by US Arp specialist. Checked over by our resident synth expert – it is in superb working order. The front panel, controls and keyboard are all superb and undoubtedly in exceptional original condition for a 2600 of this age. The keys of the 3620 keyboard are showing some age in terms of fine scratches and scuffs but overall this is also is excellent condition. The tolex has some wear and scuffs – mostly on the edges – but nothing serious. Overall this is an outstanding example of an exceptional instrument – the best we’ve seen.”