Mark Levinson No.436 monoblock power amplifier
By Larry Greenhill   •   August, 2003 All high-end audio companies turn over their product lines periodically. Even those amplifiers I have depended on as references go out of production. Although my reference amplifier can remain a part of the reviewing sequence, readers won't be able to purchase a discontinued model and get the results I describe. Thus I am compelled to get a review sample of a new amplifier or speaker, and hope for the best.

Such was the case with the Mark Levinson No.334 amplifier (reviewed in September 1999, Vol.22 No.9), which has been my reference dual-mono, solid-state power amplifier for the past four years. I was concerned when Madrigal Audio Laboratories [Harman Specialty Group since July 2003—Ed.] discontinued their entire 300 series of dual-mono amplifiers, but Madrigal's Kevin Voecks reassured me that they had a suitable replacement in the No.436.

Cool New Design
Up to now, Madrigal Audio Labs has resisted configuring their audiophile amplifiers into more compact chassis, because that would require cooling fans, which could make enough noise to distract the listener. Their Mark Levinson 300-series amplifiers had deep, massive chassis with curved front panels, silver-accented art deco curves, and sharp heatsink fins on each side. Those beautiful bulges and the amps' convection cooling meant they couldn't be stuffed into confined spaces.

But the market in high-end audio amplifiers is now driven by the requirements of home theater. Installers and customers favor amps that can be stored in racks in closets. And home-theater systems require odd numbers of channels that don't match the dual-mono approach of my previous reference, the No.334.

Madrigal has developed the single-channel Mark Levinson No.436—like the rest of its 400 series—as a low, flat, rack-mountable unit. Although the No.436 is as wide as the No.334, it's 3" shorter, 2" deeper, and 24 lbs lighter, while rated to deliver almost three times the power. Madrigal even supplies equipment racks, made specifically for the No.436, that provide conduits for dressing interconnect and speaker cables.

Gone, too, are the No.334's external heatsink fins. These fins were designed to expose a large area of metal to the air, for the passive dissipation of heat through convection cooling. But additional time and labor, hence cost, were necessary to match the colors of the heatsinks. Switching to internal sinks eliminated this requirement, lowered costs, and made it possible for the No.436 to be housed more compactly.

The No.436's thermal-management system uses crosscut heatsink extrusions mounted in a tunnel on the side of the chassis and cooled by "whisper" fans. The heatsinks are visible through a 3" by 10" rectangular opening in the amplifier's top panel. A nearby 10" by 10.25" meshed screen opening in the top panel over the main circuit boards provides additional ventilation. The low chassis, relatively flat front panel, mesh covering, and internal heatsinks seem more like elements of Japanese design than of a high-end American amplifier.

At lower operating temperatures, the heat differential inside the chassis produces enough of a chimney effect—pulling air up through the chassis—for the fans to remain switched off. At higher temperatures, the fans are turned on by a thermostat, and have a continuously variable speed to keep noise to a minimum. The fans are at the back and front of the heatsink channel; when activated, they blow air toward each other, causing turbulence. This in turn draws cool air into the ¼" space between faceplate and chassis, through the horizontal channels of the heatsink tube, and pushes it out the back of the unit. The airflow streams through the tunnels, isolated from the amplifier circuitry to keep dust from being drawn into the amplifier's center.

Description
The No.436's signal-handling and communications are managed from the rear panel. There can be found Madrigal's custom speaker binding posts, a three-pin balanced XLR input connector, an RCA single-ended input connector, and an IEC AC receptacle for the detachable power cord. For balanced operation, the tiny U-shaped shorting pin connecting pin 1 (signal, ground) to pin 3 (signal, inverting) of the XLR connector—to reduce noise pickup during single-ended operation—must be removed. Other manufacturers, such as Bryston, use a more convenient rear-panel switch for converting from single-ended to balanced inputs. Mark Levinson (and Krell) owners must keep track of these tiny pins, which can disappear quickly into the folds of a carpet if dropped.

The rear panel also has control ports that allow the amplifier to be managed by a central control system. If the amplifier is to be placed inside a cabinet, the 3.5mm minijack can connect to an external infrared receiver module. DC trigger-voltage inputs and outputs are handled by separate 3.5mm minijacks. The six-pin RJ-11, RS-232 port allows the amplifier's software-controlled operating system to be updated. This port can also be connected to a master control system such as an AMX or Crestron. The No.436 also supports two-way communication with a home automation system via two eight-pin RJ-45, PHAST-compatible ports.