Roland JC-50
A single 30 cm driver, 50 watts, and the chorus circuit that made the Jazz Chorus name — in a box small enough to actually carry.
Overview
The JC-50 pairs a single 30 cm driver with 50 W rms into an 8-ohm load, one speaker, and a chorus/vibrato section that has to work its magic inside a mono cabinet. Roland's service documentation for the model is unusually complete, and it tells you a lot about how the amp was built.
Start with the physical facts, because they matter for anyone actually hauling one to a gig. The cabinet measures 548 x 506 x 239 mm — roughly 21-5/8" wide by 19-7/8" tall by 9-3/8" deep — and the whole thing weighs 18 kg, or about 40 lbs. That's not a featherweight, but it's a genuinely portable package for a 50-watt combo with a full-size 30 cm speaker. Power consumption is listed at 150 VA. A vinyl cover came in the box as a supplied accessory, which is the kind of detail that tells you Roland expected these to be gigged and moved.
The control set is where the Jazz Chorus character lives. Owners get Volume, Treble, and Bass, plus a Distortion control and a Reverb section — and then the chorus/vibrato block: Vibrato Speed, Vibrato Depth, and a Chorus/Vibrato Select switch, alongside a Bright on/off switch. The input is a High/Low jack, so you can match the amp to hotter or weaker sources. On the back end there's a headphones output jack, and footswitch jacks for Reverb and Distortion so you can kick the ambience and the grit in and out without walking back to the panel. The chorus and vibrato are built around a BBD (bucket-brigade delay) topology — the parts list names MN3007 and MN3101 chips in the chorus/vibrato circuit, which is exactly the analog delay technology that gives these amps their characteristic wobble. The service notes even include a dedicated BBD output wave adjustment (VR-8) and a separate chorus adjustment (VR-9), which tells you Roland treated the modulation section as a precision sub-system rather than an afterthought.
The service documentation is also the best evidence of how the model evolved. The first edition of the JC-50 Service Notes was printed February 1, 1979. A second edition, dated January 15, 1983, superseded it and folded the original contents into Part 2. The serial-number split is spelled out: Part 1 covers units from 258400 and up (except USA) and 251100 and up (USA only), while Part 2 covers earlier units up to 248399, or up to 241099 for the USA. The second edition exists because the circuit changed along the way — the errata pages correct part numbers and note that a new chorus/vibrato switch (SSM043-00) and rewiring were introduced, with VR9 on the rear panel becoming obsolete on later units. Collectors chasing a "correct" early example should know which side of that serial break they're on, because the modulation switching is not identical across the run.
Inside, the amp is a conventional but solidly specified transistor design. The parts list runs 2SA970, 2SB647, 2SC1815, 2SC2240, 2SD666, 2SD667, 2SD313 and 2SD718 devices, with 2SK117 and 2SK246 FETs, NJM4558DD op-amps, and a pair of MN3007/MN3101 for the chorus. The speaker is the PD-3005C. The reverb is a spring unit (HS-700W). Power transformers were offered in 100/117 V and 220/240 V versions, with matching fuse ratings — useful when dating or re-volting a unit that's crossed an ocean.
Reception is the honest weak spot in the record here, though the archive does hold some period coverage of related Roland-adjacent gear — for instance, Modern Recording (February 1986, p.48) reviewed the Poly Tone Mini-S12L, a 110-watt RMS guitar/keyboard amp with a 12-inch speaker and a $625 price tag. The period-review material available for this model is thin and, frankly, misattributed: the two 1986 *Modern Recording* chunks in the archive describe Poly Tone amps, not the JC-50, so they can't be used to characterize this amp's sound or market position. What can be said with confidence is that the JC-50 belongs to the Jazz Chorus family whose clean, chorused voice became a studio and stage staple — but the specific contemporary verdict on the 50-watt single-speaker version isn't documented in the sources at hand. Treat any claim about how it was received in 1979 with suspicion until a real review surfaces.
For buyers today, the practical notes are these: the BBD chorus is the whole point, so any example with a dead or drifting modulation section needs the MN3007/MN3101 pair checked before you fall in love with it. The footswitch jacks and the High/Low input are simple and repairable. The 18 kg weight is manageable, but 40 lbs is still 40 lbs on a flight of stairs. And because Roland printed a second service edition in 1983 with real circuit changes, the serial number is the first thing to read — it tells you which schematic actually applies to the amp in front of you. Prices and current market values aren't documented in the available sources, so this page won't pretend to quote them.
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