The Boss Doctor Rhythm DR-110 Graphic is a drum machine, produced by the Boss product division of the Japanese Roland Corporation in 1983.
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Boss were better known for producing electric guitar accessories such as effects pedals, and the DR-110 is similarly small and lightweight in size (190×110×30mm, and only 450g), and like most Boss equipment, could be run from a 9V d.c. supply [negative centre] or batteries.
Although not designed as a high-end studio product, it nonetheless featured some noticeable advances in technology compared to previous Roland drum machines: it had an LCD graphic display, showing a step-programming grid for the various drum voices, and allowed the drum sounds to be played manually from rubber pads (as well as programmed).
Like all Roland's previous drum machines, the DR-110's voices used analogue voice circuits.
Tempo was continuously variable between 45 and 300 bpm.
The DR-110 used a 4-bit Hitachi HD33790A44 CMOS microprocessor and 1KB of μPD444C RAM memory.
In 1985, Boss released the smaller DR-220 with eleven voices. These devices had much the same functionality as the DR-110, but digital button-press control of parameters rather than knobs.
Drum sounds
The DR-110's six drum voices were:
As with most previous Roland drum machines, the bass and snare voices were generated by a "damped tuned resonance" oscillators. The cymbals and hi-hats were created by VCA-shaping and band-pass filtering a combination of white noise and four non-harmonically related square wave oscillators (generating a much more realistic sound than white noise alone). The clap sound only used shaped white noise, but was triggered by a multiple pulse train, to create a reverberation effect.
No tonal variation of the voices was possible, however (as with several earlier Roland drum machines), the relative balance between the bass and snare drums versus the hi-hat and cymbal.
An accent (volume increase) could also be added on any pattern step. The amount of accent was globally variable with a knob.
Rhythm patterns
The DR-110 offered 16 preset patterns, and 16 memory locations for the user to program their own patterns. Each pattern could be divided into 16 or 12 steps.
The DR-110 also has two "song" memories, each of which allows you to chain together up to 128 bars of patterns.
Use of battery power enabled these memories to retain their contents which the DR-110 was switched off.
Interfacing
The DR-110 could output a "V-trig" clock pulse (+6V, 10ms duration), via a 3.5mm mini-jack, to allow other slave units (e.g. arpeggiators) to synchronize to the accent section.
The DR-110 has a 10kΩ impedance unbalanced mono audio output, available on an ¼" phone connector socket. The socket was configured as the "Roland P-bus", which meant it also could be used as a simultaneous audio input, the input source being mixed with the output signal.
A separate 3.5mm headphone output socket was also present.
Sync: The standard DR110 doesn't offer any kind of external sync, but can be fitted with third party DIN-sync interfaces available from circuitbenders.co.uk or Germany's acidlabs. Internally the DR110 runs at 12ppqn (pulses per quarter note) so extra circuitry is needed to interface it with the Roland DIN-sync standard of 24ppqn.
Test Mode: Press and hold down the Start and Stop buttons when you turn on your unit. The entire LED screen show. Press your blue buttons one at the time, a big OK appear in the programming grid after last button. Turn off and then on to exit test mode and go back to normal mode.