Halcro dm88 Reference monoblock power amplifier
Trish might chalk it up to my own advancing age having compressed the passage of time, but I don't think so. I know that 2002 was eons ago. If I didn't, all I'd have to do is flip through the rest of that October 2002 issue. All of the other products reviewed—Air Tight's ATM-211 and VTL's MB-450 monoblocks, Lumen White's Whiteflame and RBH's 641-SE loudspeakers, even the VAC Renaissance Signature Mk.II preamplifier I wrote about—seem quaint, nearly archaic today. Nice gear, for sure, but somehow products of another era. That issue also included Steve Guttenberg's interviews with three of the audio industry's most prominent women: Kathy Gornik of Thiel Audio, Karen Sumner of Transparent Audio, and Rondi D'Agostino of Krell. I remember it clearly, but surely I was a kid when I first read that piece.
But I think my time warp is centered on the dm58 itself, which still seems new and avant-garde. It's not only I who feels this way—the arrival of two dm58s in my listening room last fall caused a local sensation, with both neophytes and hardened audiophiles dropping by to check out "The Halcro." Since Paul's review, the dm58's more powerful sibling, the dm68, has joined the Halcro line, the dm10 preamplifier was introduced in both full-function and line-stage guises, and the newest Halcro product is the dm38, a single-chassis two-channel amplifier. But it's still the dm58 that defines the company.
It's done and it's perfect...so let's make an even better one
For several reasons, it's important to start a review of Halcro's dm88 Reference monoblock amplifier ($39,990/pair) with a look back. First, despite the passage of nearly four years, the new amp's main competition is probably still the dm68 and dm58. Competitors have emerged, but having heard several of these, I'm confident that someone who preferred the dm58 to its contemporaries will still prefer it to anything that's come out since.
On a real-performance level, the pertinent question might be whether or not owners of the dm58 or dm68 should upgrade. However, high-end audio isn't always that logical; the real question is whether or not the dm88 distinguishes itself from the long shadow cast by its predecessors. The dm58 wasn't just a great amp, it was a demarcation point in the evolution of high-end audio and froze a moment in time. Have our collective excitement and amazement already been used up to the point where anything more is "just another Halcro"?
The other reason to start where the dm58 left off is because that's exactly what Halcro has done. The dm88 and the less powerful dm78 are updates of the dm68 and dm58, respectively. The dm58 and dm88 are the same size and weight, with the same chassis, cosmetics, and user interfaces, the same four-compartment configuration and power-factor-corrected mains supply—even the same shipping cases. In fact, having both amplifiers concurrently led me to approach the dm88's evaluation more as a Follow-Up to what's already been written about the dm58 than as a start-from-scratch review. I refer you to PB's review in the October 2002 Stereophile for a discussion of the dm58/88's configuration, design, and history.
I asked Halcro designer Bruce Candy what, exactly, was different about the dm88 and why he'd meddled with something as successful as his earlier amplifiers. "The dm88 is basically the result of a few years of contemplating how to improve the dm58/68," he said. He went on to explain that it incorporated four major changes, beginning with substantial modifications to the voltage-amplifying and power-amplifier stages to improve their linearity. Would he like to elaborate? "No, not really."
The second change, which "probably makes the biggest difference," according to Candy, was improving the magnetic shielding between the input and output stages. "Nonlinear fields generated by intrinsic nonlinearities of the output FETs are better screened from the input stages. These fields induce corresponding nonlinear voltages in the input stage and these appear, amplified, at the output. The nonlinear fields are quite significant, even at very low levels, so it's extremely important to attenuate them as much as possible."
Candy noted that the dm88's "mains-current low-harmonic-distortion power supply enjoyed benefits and simplification from the latest generation of semiconductors, capacitors, and ferrites." And finally, power for the dm88's output circuitry is generated from the output FET power stage rather than directly by the floating power supplies, as in the dm58. This change eliminates the capacitive coupling between the small-signal circuitry and power supply—always a good idea, according to Candy.
And to the $64,000 question—Why bother?—Candy responded, "My personal motivation for the design of the dm88 was the pain of knowing that improvements were possible, and I suppose this results from a flaw in my character which demands my best efforts; a perfectionist, in other words." Oh, and by the way, "technology and more thought will feed future improvements, but the present offers nothing new yet."