In Chorus mode, the dry signal is sent to one speaker while the pitch-modulated signal is sent to the other. Your ears "mix" these in the air, creating a rich, three-dimensional depth that a mono signal simply cannot replicate. 2. The Heart of the Chorus: Bucket Brigade Devices (BBD) The lush, watery chorus is driven by a component known as a Bucket Brigade Delay (BBD) JC-120 | Jazz Chorus Guitar Amplifier - Roland
Your JC-120 is a classic that deserves proper care. jc-120 schematic
This channel includes the distortion circuit and the routing for the chorus/vibrato effect. The "Bright" switch on both channels is a high-pass filter that adds top-end sparkle. In Chorus mode, the dry signal is sent
The defining feature of the JC-120 schematic is its modulation circuit. The Jazz Chorus achieves its "dimensional" sound by splitting the signal into a dry path and a wet path. The Heart of the Chorus: Bucket Brigade Devices
The is a masterclass in classic analog solid-state engineering. Its design focuses on stability, headroom, and a unique, split-path signal modulation that has never truly been replicated in the digital realm. Whether you are repairing a 1970s original or modifying a modern version, the fundamental beauty of the JC-120 circuit lies in its reliability and its unwavering commitment to producing the "Jazz Chorus" sound.
The Roland JC-120 Jazz Chorus is one of the most iconic guitar amplifiers ever built. Introduced in 1975, its distinct solid-state design offered a crystal-clear alternative to the tube-driven distortion of the era. At the heart of its legendary status—and its lush, swirling stereo chorus—is a fascinating electronic circuit.
🔧 No chorus? Check clock signal, BBD Vdd (~12–15V), and bias trimmer (often labelled VR5 or VR6).