Yamaha CP70B
A parts-list phantom: the CP70B exists in Yamaha's own service documentation, but the paper trail runs out before the story does.
Overview
The CP70B is a genuinely frustrating entry in the Yamaha catalog — not because of anything the instrument does, but because of how little survives about it. What collectors can confirm comes almost entirely from Yamaha's own Electric Grand Parts List, a service document covering the CP-70, CP-70B, and CP-80 side by side. That document treats the CP70B as a distinct variant with its own front panel, its own control panel cosmetics, and its own part numbers, which tells you it was a real, shipping configuration rather than a catalog typo. Beyond that, the record is thin.
The parts list is unusually specific about what separates the CP-70B from its siblings. Its front panel carries a different part number (AA 50 19 50) than the CP-70's (AA 50 18 60), and the control panel is split into a cosmetic "A" section (AA 50 11 00) unique to the B. Owners who have opened these up note that the panel hardware is where the variants diverge most — the CP-70B uses a slide switch for power rather than the lever switch found on some other versions, and its pilot lamp arrangement differs as well. These are small distinctions, but in a family this closely related, they're the only reliable way to tell one apart from the other on the bench.
The electronics are period-standard Yamaha. The parts list calls out NJM4558DV op-amps, FS7812L and μPC78L12 regulators, and 2SC458(C) and 2SC1345(D) transistors — workhorse components of the late 1970s and early 1980s that any tech will recognize immediately. The CP-70B also carries XLR outputs (both 3-pin male and 2-pin variants) alongside the phone jacks, which is a meaningful detail for anyone planning to use one live: it means the instrument was built to interface with professional balanced gear, not just a guitar amp.
What the documentation does not give is the thing most people actually want: what it sounds like, how many were made, what it cost, or when it was sold. The parts list is a service document, not a spec sheet, and it offers nothing on key range, action, amplification, or weight. Collectors report that CP70B units turn up far less often than the CP-70 and CP-80, which is consistent with a variant that may have had a shorter run or a more limited market — but that's an observation, not a documented fact. Treat any confident claim about production numbers or years with suspicion; the primary source simply doesn't support one.
The magazine record is no help either. The period chunks that surface for this model are studio-gear listings and classified ads from Mix and Sound on Sound, none of which actually discuss the CP70B's performance, price, or reception. That absence is itself worth noting for anyone researching the instrument: the CP70B appears to have flown under the review radar in a way its better-known siblings did not.
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