In my review of Constellation Audio’s Altair preamplifier and Hercules power amplifiers in Issue 215 I concluded that these electronics “established a benchmark against which all other linestages and power amplifiers can be compared.” Since that review, which was the world premier of the debut electronics from newcomer Constellation Audio, the company’s products have received wide critical acclaim, tremendous commercial success, and are the choice of many loudspeaker manufacturers for show demonstrations.
The name Constellation Audio might have been new when I reviewed the Altair and Hercules, but the people behind the company are anything but new to high-end audio. Constellation was founded by the principals behind the Continuum Caliburn turntable. For Constellation Audio, they assembled a team of the world’s greatest designers to create a new line of reference-grade electronics, a team that included among others John Curl, Bascom King, Demian Martin, and James Bongiorno, all led by industry veteran Peter Madnick. (Sadly, James Bongiorno, the man behind Ampzilla and Great American Sound in the 1970s, passed away January 10, 2013.)
Although the Hercules delivered reference-quality performance, its $140,000-per-pair price put it out of reach for all but the most well-heeled of audiophiles. Plus, who really needs 1100W into 8 ohms (and 2kW into 2 ohms)?
Enter the Centaur monoblock, an amplifier that isn’t a trickle- down version of the Hercules, but rather is the same amplifier with half the output power. The schematic is identical, but the Hercules features cost-no-object parts such as Vishay foil resistors. This $54,000-per-pair Centaur monoblock delivers 500W into 8 ohms, which is more than sufficient to drive all but the lowest- sensitivity loudspeakers.
The Centaur’s form factor is the more conventional rectangular chassis rather than the Hercules’ vertical tower design. A large bar running across the front panel turns the unit on and off; a tri- color LED within the bar indicates the operating status (off, on, warm-up, shut-down, mute). The rear panel offers two pairs of binding posts as well as two balanced inputs and one unbalanced inputs. A toggle switch selects between balanced an unbalanced operation. One of the balanced inputs is marked “Constellation Direct” and is used when driving the Centaur with a Constellation preamplifier. This input bypasses one entire gain stage in the Centaur. The chassis features an unusual surface texture machined into the aluminum along with ventilation holes in the side panels. The heat sinks are completely internal.
I won’t go into a full technical description here (see my Hercules review in Issue 215), but will hit the highlights. The output stage transistors are, unusually, all N-channel devices. Virtually all push- pull amplifiers employ complementary pairs of P-channel and N-channel transistors. These designations refer to the transistors’ polarity; the P-channel transistors handle the audio waveform’s positive polarity and the N-channel transistors handle the waveform’s negative polarity. But it’s impossible to make P-channel and N-channel transistors with identical characteristics; they don’t turn on and off with the same speed, introducing a waveform discontinuity at the zero crossing point where one transistor in the pair “hands off” the signal to the complementary transistor. Constellation’s answer is to use all N-channel transistors. The output stage is modular, and built around 125W elements that can be ganged together for higher output power. The Hercules output stage is built on eight such modules; the Centaur is built around four of these modules. Each module employs eight MOSFET output transistors, for a total of 32 transistors per Centaur monoblock.
Of course, the Centaur’s power supply is smaller than that of the Hercules, and the Centaur lacks the flagship’s cool functions such as the rear-panel readout of the amplifier’s operating parameters including internal temperature, output power at any given moment, and other features.