Boss Dr.Rhythm DR-550 Drum Machine, 1990, made in Japan

Link: muzines | roland [Owner's Manual]

Sound:
- Internal Sounds: 48
- Dynamic Range: 16-bit
- Max. no. of simultaneously producible notes: 12

(Pad Parameters)
- Level: 0 to 15
- Decay: -32 to +32
- Pan: 7 positions
- Assign Types: MONO/POLY/EXC 1, 2
- Tone Color: 0 to 7
- Accent Follow: -7 to +7

Rhythm Patterns:
- Programmable Patterns: 64
- Preset Patterns: 64

Songs: 8 (max. of 160 measures) Max. of 1,280 measures of successive play permissible (employing Song Chain)
External Storage: Audio-use cassette tapes
Min. resolution of timing for voicing notes: 32nd note
Tempo: 1 beat = 40 to 250


Display:
- LCD Display
- Tempo Indicator

Control Section:
[Front Panel]
- Volume Knob
- Start Button
- Stop/Continue Button
- Numeric Keys: 1 through 8
- Tempo Button
- Level Button
- Up/Down Button
- Shift Button
- Bank Button
- Voice Button
- Accent Button
- Key Pads: 1 to 12

[Rear Panel]
Power Switch

Output Jacks:
- Stereo Out Jacks; R/L (MONO)
- Headphones Jack (stereo mini jack)

Other Parts:
- Tape Save/Load Jack
- MIDI IN Connector
- AC Adaptor Jack (9 V.; for use with BOSS PSA series only) 

Normal battery life:
- Under continued use
- Approx. 9 hours (manganese)
- Approx. 23 hours (alkaline type)
- These figures will vary depending on the actual conditions of use.

Power Consumption: 90 mA
Dimensions: 188 (W) x 157 x (D) x 41 (H) mm. 7-3/8"(W) x 6-3/16"(D) x 1-5/8"(H)
Weight: 510 g. /1 lb 2 oz (including batteries)

Supplied Accessories:
- Six SUM-3 Dry Batteries
- Owner's Manual
- Preset Pattern Scores

Options: AC Adaptor (BOSS PSA-Series)