Parasound Halo JC 1 monoblock power amplifier
I haven't studied San Francisco-based Parasound Products' business or its books, but the NAD model has clearly been an influence on Parasound, which was founded in 1982. The Parasound Halo JC 1—a powerful, sophisticated premium product—was designed by a team headed by audio legend John Curl, and built for Parasound by a factory in Taiwan. It takes the outsourcing concept way upscale while keeping the amplifier's price down to a remarkable $3000 each. The 5-to-1 ratio of cost to retail price that is the norm in the audio industry suggests that the "raw" cost of the JC 1 is about $600—a number almost impossible to believe, given the superb build quality and sheer heft of this powerhouse monoblock.
For you youngsters, John Curl has been designing high-end gear since the early 1970s, including the classic Mark Levinson JC-2 and Dennesen JC-80 preamplifiers, the much-revered Vendetta phono preamplifier, and lots of electronic gear for the Grateful Dead. Curl has designed Parasound products since 1989, most to specific price points and aimed at the very competitive middle of the high-end market. By ultra-high-end standards, $6000 is not a lot for a pair of monoblocks amplifiers, but it's a big enough step upmarket for Parasound that the new Halo moniker distinguishes the line from other Parasound products.
The JC 1 is a brawny brute weighing 64 lbs. It outputs 400W into 8 ohms, 800W into 4 ohms, 135 amps of peak current, and 25W of pure class-A power into 8 ohms. According to a blurb by John Curl that accompanies the amp, the design is "based on a complementary differential J-FET input stage followed by two stages of selected push-pull MOSFETs ultimately driving nine pairs of the most powerful complementary bipolar power transistors that are available today."
Curl describes the JC 1 as an outgrowth of his Parasound HCA-2200 from 1997. The JC 1 has much larger heatsinks, twice the power supply, better internal componentry and layout, and its range of operation in class-A has been extended to 25W, which should be enough to keep it from class-AB operation on all but the most demanding musical passages. Even at idle, the JC 1 puts out plenty of heat, so ample ventilation is critical. A switch on the rear allows users to drop class-A operation down to 10W for placement in tight spaces. The direct-coupled design uses a fast-acting DC servo circuit to keep DC from ever reaching the output. Protection for both amplifier and loudspeaker is also provided by a gold-plated relay, and by current-sensing transistors that will open the relay if the current draw exceeds a predetermined amount, whether due to the impedance dropping below 1 ohm or a short at the speaker terminals.
Curl designed the circuits; Bob Crump and Carl Thompson, his partners at CTC Builders (makers of the custom-built Blowtorch preamplifier), did most of the hands-on work. Thompson engineered the boards, Crump chose the parts and "voiced" the finished product. According to Crump, the JC 1 grew out of a CTC-modified Parasound HCA-3500 called the CTC BBQ, which was demoed at the 2001 Consumer Electronics Show. Among the upgraded parts used in the JC 1 are a 10-amp toroidal transformer enclosed in a steel canister filled with epoxy resin, Sanken output transistors, Harris hyperfast soft-recovery diodes, Nichicon Muse DC and local bypass capacitors, Nichicon Great Supply raw DC capacitors (for a total of 132,000µF capacitance), and Vampire continuous-cast copper wire and gold-plated OFC RCA jacks. Separate power supplies for the input, driver, and output sections are said to make the JC 1 totally immune from AC-line voltage fluctuations.
The physical plant is a handsome chunk of gleaming, heavy-gauge aluminum fitted with large heatsinks on either side. Rear-panel fittings include balanced and single-ended inputs, two sets of five-way binding-post outputs, a ground "lift" switch for when there are hum problems, and a bias-level switch allowing for reduced bias current, and thus cooler operation if needed. There are also facilities for automatic turn-on (by an audio signal or an external trigger voltage), which can be daisy-chained to turn on other components. While no audiophile would want to listen to this or any solid-state amp from a cold start, the JC 1 has been designed for home-theater use—five of these beasts left running continuously could generate an enormous amount of heat and large electric bills. In fact, the JC 1 is certified THX Ultra2—which means it meets certain amplifier standards set by THX for home theater.