Parasound HCA-2003
Fifty-four pounds, three channels, and enough reserve current to dim the lights - John Curl's THX-certified muscle amp for the front stage.
Overview
The HCA-2003 is a three-channel power amplifier, and the odd channel count is the whole point. As Audio (November 1996, p.34) explained in its equipment profile, a three-channel amp lets an owner take a separates-based stereo rig, add the amp, add Dolby Pro Logic or Dolby Digital processing and a few new loudspeakers, and end up with surround sound. The new amp drives the left/center/right "front stage," which carries most of a home theater's acoustic load. Parasound built the 2003 for that job. The magazine's reviewer, Daniel Kumin, noted that even in a surround system the amp spends plenty of its life reproducing plain stereo and mono, so the left and right channels need all the headroom of a good stereo model.
The amplifier is the latest in Parasound's High-Current Amplifier series, designed by John Curl - described by Audio (November 1996, p.34) as one of the godfathers of modern wideband amplifier engineering. It meets Lucasfilm's Home THX criteria for power amplifiers and is certified. Rated continuous output is 200 watts per channel into 8 ohms and 300 watts per channel into 4 ohms, all three channels driven, 20 Hz to 20 kHz. Peak current capacity is 60 amperes per channel. Rated distortion is under 0.05% THD at full power and under 0.006% at typical levels.
The internals are more serious than the spec sheet shows. Each channel gets an independent power supply, all fed from a common 1.2-kVA transformer with separate windings per channel. Behind them sit 90,000 microfarads of "computer-grade" supply filtering, separately regulated driver-stage supplies, and hand-picked complementary MOS-FET high-voltage drivers. The output stage uses 12 complementary pairs of beta-matched, 50-MHz, 15-ampere transistors, direct-coupled to the load with no LCR output networks. Linear-tracking, instantaneous-acting DC servos handle DC protection. The input stage is a cascode Class-A circuit using matched complementary J-FET pairs. Parasound specifies overall operation as high-bias Class A/AB, and the amp's distinctly warm idling behavior tends to confirm that. It runs just cool enough to keep a hand on comfortably.
Physically it's a big one: 19 inches wide, 7 inches high, 16 inches deep (with feet, roughly 7⅝ inches tall), and 54 pounds. Construction is not fancy but very solid, with heavy-gauge sheet metal front, rear, top, and bottom, and very large heat-sink extrusions forming the sides. Those sinks have generous 1½-inch-deep ribbing with rounded profiles, which cuts down on the cuts and scrapes sharp-cornered heat sinks so often inflict. Rack handles front and rear make it manageable for a reasonably fit person to move.
On the bench, the numbers held up. Audio (November 1996, p.38) measured A-weighted noise at −99.1, −99.3, and −99.6 dBW across the three channels, with no audible mechanical hum or buzz, which is unusual for a multichannel amp. At rated power, THD+N stayed below 0.05% into 8 ohms and 0.08% into 4 ohms, with good linearity well into the ultrasonic and infrasonic regions. The amp clipped at about 265 watts into 8 ohms and 323 watts into 4 ohms, comfortably beating its ratings. On IHF tone bursts it delivered 288 watts into 8 ohms and 487 watts into 4 ohms, roughly 1.6 and 2.1 dB of dynamic headroom. Channel separation was excellent, especially for a multichannel design where board-trace routing is cramped. The test bench even survived an accidental 10-volt input blast. The amp tried to make 3,000 watts, shut down, and powered back up after a cooling-off period without complaint.
Sonically, Audio (November 1996) came away impressed by the HCA-2003's effortless handling of widely dynamic, full-range sound. On high-impact material it delivered substantial, low-end-rich transients with a smooth, no-sweat quality and none of the fat, glugging tinge lesser amps show when swamped. Jazz and full-orchestra recordings came across neutral and open, free of extra air or brightness yet clear and detailed. If forced to assign a character, the reviewer put it just barely on the warm-and-rich side rather than cool-and-analytical. It was transparent without exaggerating shimmer, and free of hardness or edge. Bottom-octave depth and control were called outstanding, and the review said anyone needing an amp for a three-subwoofer home theater would find it ideal.
Original price was $1,650. For collectors today, the HCA-2003 is a niche piece. Three channels limits its appeal to stereo purists, but for a surround or biamp setup it's a lot of John Curl-designed, THX-certified amplifier for the money, and its build quality and protection circuitry have aged well. The usual caveats for a 54-pound Class A/AB amp apply: it runs warm, wants breathing room, and shipping one is a two-person job.
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