Roland CSQ-600
Four parts, six hundred notes, and a DIN cable that made the TR-606 and Jupiter-8 speak the same clock.
Overview
The CSQ-600 is a digital sequencer. The service notes sum it up in one line: 600 notes of storage, divided as 150 notes across four parts. The four-part split is the interesting bit. This isn't a single-line sequencer that you chain into a song. It holds four independent musical lines in memory at once, which is why Roland's own documentation pairs it with polyphonic instruments as readily as monophonic ones. A CSQ-600 driving a Jupiter-8 and a CSQ-600 driving an SH-2 are both legitimate uses of the same machine.
The CV and gate specs show what era this belongs to. CV input runs 1V/oct, 0V to +5V. CV output runs 1V/oct but spans -2V to +8V. That asymmetry is deliberate, and the service notes explain it: the CSQ-600 can transpose playback by summing an external key voltage with the stored CV, so a 2V key reproduces the original pitch and 0V drops the part two octaves. Gate input triggers at a +2.5V threshold. Gate output switches between 0V off and +15V on, the same +15V logic the rest of Roland's early-80s sync ecosystem expects. Clock runs 700Hz to 4.7kHz, and the step pulse input shares that +2.5V threshold.
Sync Load is what makes the CSQ-600 more than a note recorder. According to the service notes, the unit holds a "Quasi-LOAD" state for two measures after you press LOAD/STOP. The LOAD LED lights, but the CPU is still inhibited from accepting CV and gate data. That window lets the performer set beat and tempo for the rhythm before the sequencer starts capturing. The notes are blunt about getting it wrong: missing gate signals at the start of real-LOAD mode, caused by playing a note too early, produce "RESET" loadings. It's a quirk, not a bug, and it has bitten every CSQ-600 owner at least once.
The sync side is where this thing earns its place in a rack. It talks to the TR-606 over a five-pin DIN connection carrying start/stop, ground, and clock. The TR-606 manual lists the CSQ-600 by name as a sync partner, and the pinout matches. Modern Recording (November 1980, p.33) noted that Sync Load also lets several CSQ-600s run in parallel and stay synchronized, so a stack of them could drive multiple synthesizers or feed a single polyphonic instrument. That was unusual for 1980, and it's the reason the CSQ-600 shows up in rigs that also contain a Jupiter-8 and an MC-4.
Internally, the CSQ-600 is a successive-approximation converter. Analog key voltages come in, get converted to digital for RAM storage, then get converted back to analog on the way out. The RAM holds 5V of analog range, which at 1V/oct works out to 61 notes. Data is stored as 8 bits, with 24 subtracted after A/D conversion so that 0V reads as zero in decimal. Each digital step equals roughly 83.3mV, the potential difference between adjacent keys. The conversion is handled by a comparator (a 311) that sets and resets bits from DB6 down to DB0, seven passes per sample.
Power draw is 8 watts, which is modest enough that the unit barely warms up. Dimensions are 508(W) × 305(D) × 105(H) mm, and net weight is 5kg.
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