Parasound Halo JC 2 Design Overview.

John Curl’s famously symmetrical circuits give the listener the best chance to experience the full emotional content of the source. In the JC 2 the physical implementation of the circuits closely follows the circuit topology and the layout is as literal as possible, commensurate with isolation of disparate or out-of-phase signals. All component parts are oriented for minimum interaction. The high current, low impedance audio power supply is larger than many power amplifiers, and is carefully integrated with the signal boards. The resulting musical output is rich with absolute musical authority and clarity.

The chassis and PCB layout of the JC 2 are uncompromised in their pursuit of the highest design goals for a preamplifier. The shortest signal path is achieved by placing the master volume control and individual channel level potentiometers and high quality gold-plated input select relays right where the input circuitry is located to eliminate the need for long wires and traces. Each channel is on a separate PCB. The preservation of low-level signals is achieved by the separation of critical audio signals from non-audio circuits. The audio power supply, control power supply and control circuits also have dedicated PCBs. To prevent the possibility of radiated noise getting into an audio circuit the power supplies and control functions are further isolated from each other by two 3/8 inch thick aluminum partitions that are the full height of the chassis and run side-to-side and front-to-back. The entire signal path is embedded on circuit boards in a continuous ground plane or carried in professional-grade Canare® shielded wires.

Even within the audio circuit’s power supply section, AC power is isolated from regulated power by placing the power transformer high in the chassis on one of the aluminum partitions. The power transformer is an R-core type, which has the advantage of a toroid transformer for minimizing radiated hum but is superior at preventing noise carried on the AC power line from passing into its secondary windings. Ground return paths are low resistance, with substantial planes and thick wires, and sequenced precisely. Non-audio control circuitry, LEDs, relay coils and the motor for the master volume control are powered by a separate power supply whose transformer has a separate ground return. The resulting extremely low noise levels enable musical nuances to overlay an utterly silent background.

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