Boss DR-660 Dr. Rhythm (1992)
Two hundred fifty-five drum tones, twelve voices of polyphony, and a service manual that treats the cymbal circuit like it matters.
Overview
The Boss DR-660 is a desktop Dr. Rhythm drum machine dated April 1992 in its own service documentation. The date stamp shows up in the troubleshooting section and in the ROM version display, where the unit reports a version string beginning "92Mar01." That firmware date is the firmest anchor the documentation gives. The archive can't currently state production start or end years beyond it, and this page won't guess.
What the service notes do establish is the shape of the machine. It's a compact desktop unit, 215 mm wide by 165 mm deep by 57 mm tall (roughly 8-1/2 by 6-1/2 by 2-1/4 inches), powered by a BOSS BRA-series AC adaptor rather than batteries. That footprint puts it in the same territory as the DR-550 and the later DR-880: a box meant to sit next to a guitar amp or on a keyboard stand, not in a rack. The manual's table of contents is unusually revealing for a drum machine in this class. Alongside the expected specs, exploded view, and parts list, Boss gave a section to "Deterioration in the Conductive Coating Inside the Case" and another to "How to Stick the Conductive Tape."
The voice architecture is where the DR-660 earns its keep. There are 255 internal tones, which the service notes list flatly as "Number of Tones: 255," mapped across 100 preset patterns and 150 programmable patterns. Polyphony is 12 notes, and the troubleshooting section is candid about what happens when you exceed it. The manual's entry for "Sound breaks" lists "more than 12 voices are being played simultaneously" as the first possible cause. That's a real ceiling for a machine in this bracket, and anyone layering dense tom fills or stacked cymbal work will hit it.
Songs run to 100 slots, each holding up to 250 parts, for a total song-part capacity of 900. Resolution is 96 ticks per quarter note, the same figure the DR-880 would carry years later. That's enough to place ghost notes and flams with reasonable precision, though it's not a high-resolution sequencer by any stretch. The effect section is limited to reverb and chorus, and the manual's troubleshooting entries suggest those are the only two processing options the machine offers. Power comes via the BOSS BRA-series AC adaptor. The spec table in the service notes lists a noise level of "BdBm (DIN AUDIO) (L/mono)," an OCR artifact in the source document that the archive can't resolve into a clean figure, so it is flagged rather than reported as a number.
The pad layout and workflow follow the same menu-driven approach Boss used across the Dr. Rhythm line. The troubleshooting section reads like a record of how owners actually use the thing. Entries cover flams not triggering because the flam interval is set to zero or the ratio is wrong, patterns changing because key-pad assignments were altered, songs auto-chaining because the song chain function is on, and tempo shifting at song start because an initial tempo was set. These are the confusions of a machine with deep menu settings and a small display.
MIDI implementation is thorough for the period. The service notes include a data save-and-load section explaining that RAM contents are transferred to external memory via MIDI exclusive messages. There is no floppy drive, no cartridge slot, no SmartMedia. The troubleshooting section documents the MIDI mode toggles that owners will eventually trip over: "4PRG" for program change, "5RxVOL" for MIDI volume, "6RxEXPR" for MIDI expression, "7RxEXC" for exclusive messages, and sync mode for whether the DR-660 follows external clock or free-runs. Each one has a matching "no sound" or "cannot be controlled" symptom in the manual. A mis-set toggle gives you silence rather than an error message.
The memory backup battery is the other maintenance item the manual flags directly. Its error message appears at power-on when the backup cell is exhausted, and the recommended action is battery replacement. A second power-on error covers corrupted memory data, which the manual says can be cleared by pressing ENTER to initialize. The factory preset data can be reloaded by holding RESET and REC while powering on, then confirming "INIT?" and "SURE?" The service notes walk through that procedure step by step.
The conductive coating issue needs its own note. Boss included instructions for re-sticking conductive tape inside the case, which points to shielding deterioration as a known long-term wear item on this model. Anyone buying a DR-660 today should treat the interior shielding as a consumable.
Period coverage of the DR-660 in the UK press is thin. Sound on Sound (September 1995, p.137) ran a roundup of digital audio and MIDI accessories that mentions neither the DR-660 nor its immediate siblings. Later classified pages from the same publication (July 1998, p.181; October 1998, p.282) show no DR-660 listings, so the machine doesn't turn up in the secondhand columns the way the TR-808 or the DR-110 do. The DR-660 is a documented, serviceable, MIDI-capable drum machine that never attained the cult status of its more famous relatives.
The DR-660 offers 255 tones across 250 patterns and 12-voice polyphony, and its service manual states the limits openly. It is a working desktop drum machine from 1992, and it is not a TR-808.
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