Sequential Circuits Pro-One — Vintage Monophonic Synthesizer

Best for

Vintage monophonic analog synthesis with onboard sequencing and arpeggiation, where exact-unit inspection and maintenance are acceptable parts of ownership.

Who should skip

Skip it without exact-unit voltage, function, serial, service, modification, and condition evidence, or if modern support and predictable maintenance are required.

Watchouts

Treat every used Pro-One as a distinct physical offer. Verify voltage, serial and revision evidence, keyboard and control behavior, audio and control connections, modifications, service history, photos, cosmetic condition, and inclusions for that unit only.

Verify before buying

• What serial, revision, and operating-voltage evidence belongs to this exact unit?
• Do the keyboard, oscillators, filter, envelopes, sequencer, arpeggiator, controls, and connections function correctly?
• What documented service, repair, or modification history is available?
• Which seller photos, cosmetic notes, and included items belong to this physical unit?