ARP 2600 & 3620 Keyboard

It’s a model 2600P which the tech has dated (as best he can) to ’75 or ’76. This model ARP has the most desired MOOG ladder style Copper clad 4012 filter. See below for more information on modules, which “version” it is, whether it is one of the “good” ones.

Complete professional service completed in February 2018 by US Arp specialist. Checked over by our resident synth expert – it is in superb working order. Ready for the next 45 years of spectacular sound and music creation.

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Exactly what “version” 2600 is it? Is it one of the “good” ones? 

This one has the serviceable (non-‘potted’) modules. Oscillators are 4027-1. These machines are normally found in the 73-76 time span. According to the engineer (with 30 years’ experience of Arps), people who worked for Arp have told him directly production was fairly chaotic. While some sources online will say that this or that version sounds “better” or “best”, the reality is that variations are common between modules even if they were made the same year due to manufacturing inconsistencies (or as he put it, ‘they just got soul!’).

It would seem that there is not a simple chronological timeline of production of the various model types. Like most smaller gear manufacturers of the ’70s, Arp didn’t operate on a rigid structure: suggesting that 1970s handbuilt synths have similarly linear/traceable timelines to those made on a modern factory production line is divorced from reality.

Our tech’s best guess is that this is a late 1975 / early 1976. It has the older front panel but still has the 4027-1 OSC and 4012 filter modules that are all possible (although far from easy) to service.

He is of the opinion that this is a superb-sounding Arp and an excellent example, and we wholeheartedly agree!

Service work included:

• All new high-end capacitor power supply upgrade
• New powerful mains transformer to ensure pitch stability
• Multi turn high end trimmers on power supply upgrade
• All circuit board tantalums replaced with high end capacitors
• All pitch CV trimmers replaced in the complete pitch CV chain including the 3620 duophonic keyboard (to ensure extreme tuning stability)
• Factory specification calibration
• New Cinch Jones receptacle (for keyboard connector)
• New Pratt Reed bushings in the 3620 duophonic keyboard

Includes:

• ARP 3620 Duphonic keyboard with original lid (Matching number with the 2600)
• ARP 2600 Original user manual
• ARP 3620 Original user manual
• ARP 2600 Portamento pedal – New unused (tested once) – comes in original box
• ARP 2600 “blind plug” (rare)
• 4x 16″ patch cables
• 4x 38″ patch cables
• ARP Original paper envelope

Extensively tested by our resident synth expert – all features and functions are working as they should (as with much vintage gear some crackle is possible from sliders especially if the unit has not been used for while, but this should clear with use).