Parasound HCA-2200
A John Curl high-current design that ran with the big monoblocks and left owners wondering how Parasound pulled it off for the money.
Overview
The HCA-2200 is a stereo power amplifier built around John Curl's high-current design philosophy. The numbers tell you right away it is not a polite little box. Parasound rated it at 220 watts per channel into 8 ohms, rising to 385 watts per channel into 2 ohms in stereo. Bridged to mono it was rated at 750 watts into 8 ohms and 1,000 watts into 4 ohms - all at 0.07% THD per the company's published specs. The current figure is more telling than the wattage: 50 amperes RMS and 90 amperes peak. That kind of current delivery lets an amplifier stay composed into low-impedance, reactive loads that make lesser designs fold.
The topology is part of the story. The first-generation HCA-2200 used Class-A cascode input circuitry and MOS-FET driver transistors with fully balanced inputs. It stayed in Class-A up to about 6 watts of output, then slid into Class-AB. Inside are two 1.2 kVA toroidal transformers - one per channel - and 100,000 microfarads of filtered power storage. The large filter capacitors are bypassed by smaller film caps, a tweak usually associated with modifiers rather than factory builds. The output stage runs twelve high-bias bipolar devices per channel, and the side-mounted heatsinks run hot because of it. A reviewer noted the amp reaches roughly the same temperature at idle as it does wide open, which is the signature of genuine high-bias Class-A operation rather than a fault.
Bandwidth was rated at 20 Hz to 20 kHz, ±0.5 dB at rated power, and 3 Hz to 90 kHz with a 0, -3 dB window. Damping factor exceeded 120 at 20 Hz. Rated THD at typical listening levels was a claimed 0.005%. The rear panel carried XLR balanced and RCA unbalanced inputs with per-channel toggle selection, dual five-way binding posts for bi-wiring, and a stereo/bridged-mono switch. Owners coming from earlier Parasound designs note the 2200 dropped the front-panel attenuator pots of prior models and gave you five-way binding posts instead of spring clips.
The measurements backed up the marketing. Audio tested the HCA-2200II and found voltage gain of 27.1 dB with IHF sensitivity of 125.0 mV. Frequency response was essentially unaffected by 8- or 4-ohm loading, and the 3-dB down point sat at about 200 kHz, with rise and fall times of 1.6 microseconds. Square-wave response showed no tilt at 40 Hz, evidence of extended low-frequency bandwidth, and ringing into a 2-microfarad capacitive load was well damped. Interchannel crosstalk measured better than 100 dB down up to about 1 kHz, rising at 6 dB per octave to roughly 77 dB down at 20 kHz. The same review called the harmonic distortion spectrum at 10 watts into 8 ohms something that "would make any amp designer proud" - little beyond second and third order, plus noise.
Period reception was unusually strong for a mid-priced amp. HiFi-Stereo (July 1993, p.18) reported the HCA-2200II was said to operate in Class A until output reached 6 watts, with a stated damping ratio of 114 dB and THD of 0.05 percent at full power. Audio (April 1994, p.55) printed the most quoted verdict, which Parasound reprinted everywhere: the HCA-2200II was "a benchmark product against which other amplifiers can be measured," with virtually unlimited brute power but enough finesse to let the music through. Stone reportedly ran a pair against Apogee full-range speakers and found them on par with far more expensive monoblocks, praising their flexibility and price. Audio characterized the sound as slightly laid-back in the upper midrange and treble - easy to listen to, with very little irritation, very good detail and space resolution, and excellent dynamics and bass control.
There is a version wrinkle. The original HCA-2200 (circa 1992, around $1,585 suggested) and the later HCA-2200II are distinct revisions. Parasound's own advertising touted "30 improvements" to the premier amplifier, including a modified power supply board, higher-speed 15-amp output transistors, improved 60-ampere speaker protection relays, separate coarse and fine bias trims, and a custom hand-fabricated AC cord. Buyers should confirm which revision they're looking at, because the suffix matters for parts and resale. The amp runs hot by design, so ventilation is not optional. The high-bias output stage means the heatsinks are doing real work, so give it room. Collectors treat the Curl-designed HCA-2200 as one of the value landmarks of early-'90s high-current amplification: a heavy, balanced-input, bi-wire-capable amp that measured clean and sold for a fraction of the iron it was compared against.
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