Mark Levinson No.532H power amplifier
The No.532H is the latest model in a product line that spans four decades and has given us 76 different audio products. Mark Levinson Audio Systems (MLAS) opened for business in 1972 in an industrial park in Woodbridge, Connecticut, under the leadership of Mark Levinson himself, a marketing guru who has claimed to have discovered the high-end audio market. John Curl, MLAS's first designer, created several models that screamed audiophile eccentricity and purism: the jet-black JC-1 and JC-2 slimline preamplifiers; the sharp-finned, low-powered, 25W ML-2, a monoblock capable of operating in class-A almost regardless of the load. When Tom Colangelo took over from Curl, he developed the huge, back-breakingly heavy ML-3 stereo amp, designed to drive at high power speakers of even more impossibly low impedances, and the dizzyingly expensive, four-chassis ML-6 preamplifier, an all-out effort to achieve sonic purity through physical minimalism. From this phase of ML's history I own a pair of Curl ML-2s (bought several years ago on eBay) and a Colangelo ML-7 stereo preamp.
Despite new, more sophisticated designs, including professional open-reel tape decks and modularized preamplifiers, MLAS experienced significant financial difficulties in the mid-1980s. These were resolved with the company's purchase by Madrigal Audio Labs, followed by a reorganization of personnel, an increase in engineering staff, and a dose of fiscal discipline. Under Madrigal's leadership, new amplifiers were brought to market, including the No.23 and No.27 series, the more expensive Nos.20, 33, and 33H Reference-series monoblocks, and the Nos.331336 series of dual-mono amps. Madrigal's styling for these amplifiers set a high point in industrial design: black military-style amplifier chassis adorned with huge heatsinks, and curved, art deco faceplates in silver and black. On the test bench they "doubled down," increasing power output as the impedance load dropped. I reviewed in Stereophile the No.27 (June and July 1990, Vol.13 Nos. 6 and 7), the No.27.5 (July 1993, Vol.16 No.7), the No.331 (January 1996, Vol.19 No.1), and the No.334 (September 1999, Vol.22 No.9).
In 2001, Harman International purchased ML, shuttered Madrigal Audio Labs, and moved the company to Harman Specialty Group's facility in Bedford, Massachusetts. There it shared sales and manufacturing space with Lexicon, and brought to market the 400Wpc No.436 (August 2003, Vol.26 No.8) and the 200Wpc No.431 (May 2005, Vol.28 No.5). These were configured as low, flat chassis cooled by convection: air rising through slots in the bottom plate passed over internal heatsinks and out the top plate. The No.436 augmented this with a fan for sustained high-power operation.
Harman produced no new amplifiers until 2009, when it reorganized its high-end brands into the Harman High Performance Audio Video division (HPAV). It later relocated to Elkhart, Indianathe original production site of the Crown DC-300A amplifierwhere the cost-no-object class-D No.53 is also manufactured.
External Simplicity and Inner Beauty
The matte-black No.532H ($8500) is the most no-nonsense stereo amplifier in the HPAV line. Its monotone black chassis differs from its more expensive stablemates, the No.532 stereo amplifier ($20,000) and the No.53 Reference monoblock ($25,000 each). These flagship products have prominent external heatsinks and black and silver accents. The No.532H is almost identical in size to the No.431, which I reviewed in 2005, being only 9mm less deep and 21 lbs lighter; it's also 100Wpc more powerful and $1500 more expensive.
Harman redesigned the H-series amps to be reliable and serviceable in the field. All built on the same chassis, they range in weight from 55.5 lbs for the single-channel No.531H to 98.5 lbs for the five-channel No.535H. Aside from the No.535H, each model also uses the same 300Wpc internal amplifier module, its printed circuit board bolted to the back of a 16-fin internal heatsink. This module has 14 small, 50V, 3300µF power-supply capacitors instead of the more traditional and huge "soda can" electrolytic caps; two relatively small (by ML standards) 436VA toroidal power-supply transformers are bolted to the inside of the faceplate.
Inside, the No.532H maintains traditional ML design values with independent power-supply components for each 16-output-device channel, convection cooling, curved PCB traces, large power-supply capacitance, and a fully differential circuit for the signal path. Its separate chassis and signal grounds are said to minimize noise for listening at low levels. Though the No.532H isn't rated into loads other than 8 ohms, its current-feedback output-stage design is claimed to remain stable into 4 and 2 ohm loads.
Curious about the No.532H's internal workings and build quality, I unscrewed the eight flat-head screws that secure its top plate, which is shaped like an inverted U. This revealed the chassis, also U-shaped, which contains only two slim amplifier modules and the two big toroidal power transformers. The chassis is big enough to accommodate up to five amp modules, each bolted to the chassis bottom via its heatsink. Signal and power connections are on a small PCB at the inside left edge of the rear panel. Another circuit board is screwed to the left wall of the chassis, just behind a cutout that grants access to two replaceable fuses and the jumpers for setting the No.532H for the voltage of the country in which it's to be used. A small fuse is mounted on each amp module, near the power-supply caps.