PS Audio HCA-2 power amplifier Kal Rubinson Review
It is Stereophile's policy not to rush to publish the first review of a product, but to take the time to be thorough, reflective, and responsible. But in the case of the PS Audio HCA-2 amplifier, so many comments have already been published, even in Stereophile, that by the time this review sees print it might seem like old news.
First, PS Audio released a good number of beta samples of the HCA-2 to their website subscribers, and posted many of those subscribers' comments. That created a good deal of consumer interest—a welcome byproduct of beta testing. Second, with all that word-of-mouth there has been a buzz on all the audiophile websites, including the perennial question about why there seem to be so many HCA-2s offered for resale. (I don't know the answer to that question, which is often asked about some of the best equipment made.) All of this made my head spin—after all, Paul McGowan of PS Audio kept assuring me that I'd be getting one of the very first HCA-2s. When, early in May, McGowan dropped by with a regular production sample, I had the feeling that I was perhaps the last audiophile in North America to hear one.
Finally, by the time I got around to living with the amp, formulating my ideas about it, and transferring those ideas to (virtual) paper, Sam Tellig had already had his unique way with the HCA-2, and John Atkinson had already placed it in Class A of "Recommended Components" (both in the October 2002 Stereophile). Fortunately, those recommendations saw print so late in my deliberations that they had no influence on my considerations, and only a bit on my comments.
Despite all the ballyhoo, I was surprised to see how compact and clean the HCA-2's design really is. Although it's no bantamweight—its weight is the same as the Bel Canto eVo 200.2's but feels like less—the HCA-2 can be easily hefted into whatever space you have for an amp. I mean any space: The HCA-2 is not only trim in size, it seems to generate almost no heat. The front panel has a sculpted On/Off switch on the left side and an illuminated blue "PS" logo on the right of a broad, black rectangular panel. Turn the HCA-2 on and the word "Standby" appears in yellow, replaced after about 15 seconds by "Operate," in blue. There's a red "Fault" indicator, too, but I never saw it illuminated.
The rear panel is nearly as simple. On the right are paired unbalanced (RCA) and balanced (XLR) inputs. In the middle are four sturdy WBT binding posts for the speaker cables. On the left is the IEC power input, a power-line fuse, and a switch for selecting between AC voltages of 100-120V and 220-240V. Above the power utilities are modular connectors for an automation controller bus, DIP switches to identify the HCA-2 on the controller bus, and a 12V DC trigger input for simpler control systems. There are no external heatsinks, and the only ventilation opening is on the chassis' left side.
Inside, the simplicity continues. The contents (and the weight) are dominated by the power supply, which includes a hefty toroidal transformer and the basic components of a High Current Ultimate Outlet, PS Audio's widely appreciated line conditioner. The actual amplifier pcb with power output stage is almost minuscule, and would probably fit in the chassis of the little Nagra PL-L preamp that I paired with the HCA-2 for a part of its workout.
The October 2002 "Sam's Space" includes Sam's lighthearted but informative exchange with Paul McGowan detailing the unusual engineering ideas incorporated in the HCA-2, so I'll be brief: The input stage, a fully balanced analog class-A design using J-FETs, feeds a high-speed-switching output stage called an SDAT, for Super Digital Amplification Technology. This class-D power stage is fully balanced, load-insensitive, and extremely efficient. Moreover, after leaping off the PS Audio drawing board and into the measuring lab, it was modified based on the results of extended listening sessions.
Okay. Paul McGowan, the P in PS Audio, did drop off the HCA-2 himself. On the one hand, this is not something that the average purchaser can expect. On the other, I didn't let him install the amp. I'm an audiophile—nobody gets at my connections but me.
I plugged in the HCA-2 between the Sonic Frontiers Line-3 preamplifier (via AudioQuest balanced Pythons) and the Revel Ultima Studio loudspeakers (via Harmonic Tech Pro-9 Plus, internal biwire), played a few selections, then let McGowan play a few of his. The HCA-2 sounded okay (I maintained a stone face), but McGowan asked me when I was going to get subwoofers, and said that the amp would need a few hundred hours of break-in before it would truly show its mettle. Little did he expect what it would get.
The next day, we Rubinsons began major renovations to our apartment, and placed all audio components out of the reach of anything but the Sonic Frontiers' remote control. For three months (!), the HCA-2 was fed an almost continuous diet of WQXR-FM. Any premature assessment of the break-in process was impeded by the several layers of plastic sheeting we'd hung to shield the listening room from the demolition. I also left the system running over the weekends, when we lit out for places less dusty.
So if anyone thinks that the HCA-2 needs more break-in than this, he might also inquire about extending PS Audio's three-year warranty.