An analog drum machine produced by BOSS in the eighties.

  • Six, sixteen step patterns and two twelve step patterns, each with an A and B variation, allowing for effectively sixteen different patterns, total
  • Bass drum, snare drum, rim shot and accent instruments.
  • A fixed hi hat which will play either every beat or every other beat, or not at all.
  • Volume, tone, tempo and accent knobs. The volume knob doubles as a power switch. The tempo knob is totally analog and gives no indication of BPM. Tone effects only the bass drum, as far as I can tell. The accent knob controls the volume of the accent applied to each note.
  • Start and stop patter buttons, which dual as sixteenth note and rest in pattern edit mode.
  • DBS and CSQ outputs. These were wacky BOSS proprietary beat synching schemes which have since died, slain by the industry standard MIDI.
  • A phono out and foot switch input. The footswitch is used to start/stop the machine.
The box itself is about the size of a paperback novel, with a dull black finish and white lettering, except for the BOSS logo which is typical orange. It runs on one nine volt battery.

The main problem with this drum machine is that unlike other comparable machines of the era (the 909, etc) the pattern input is done by stepping through the sequence of 12 or 16 notes and setting a sixteenth note or rest for each beat, for each instrument. This is opposed to the other, more user friendly method of having each beat as an individual button with LED above it, indicating whether the beat is to be played for whichever instrument is selected. The DR-55's interface requires a good sense of rhythm and visualization, as one has to count through each intstrument and envision how the three instruments (and accent) will mesh, without any output other than an LED which pulses when the beginning of the pattern is reached again. This tricky concept, combined with a lack of variety in instruments, limits the use of the DR-55 to hobbyist use.

A modification exists to add a user control for the bass drum decay. It's pretty simple, but requires some soldering skill. If one pops open the case of the DR-55, on the bottom left of the circuit board, near the tone potentiometer, there should either be a tiny taper pot or a resistor. The taper pot only exists on the older models, and can adjust the bass drum decay. If you have a model with the resistor, simply snip it out and replace it with a potentiometer of a low resistance. You may have to play with the amount of resistance to get the action you want from the control. After this mod is performed, there is a greater range of use for the machine, since the bass drum actually sounds quite nice with more decay.