|Mark Levinson No. 436 Monaural Power Amplifier|
|Home Theater Power Amplifiers Mono Amplifiers|
|Written by Bryan Southard|
|Wednesday, 01 January 2003|
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When purchasing automobiles, you are presented with a selection that varies from simple low-cost transportation merely designed to supply the most basic features and a means from point A to point B, to vehicles that are the very essence of performance and artistic expression. When purchasing audio/video products, you have an equally enchanting array of choices, designed to fit every budget and performance desire. The Mark Levinson No436 is a product designed for the audio/video enthusiast who demands nothing short of the highest performance that money can buy.
Madrigal is no stranger to this level of performance with lines that include Revel and Proceed and are no stranger to me, as I own and use Revel Salon loudspeakers and the Mark Levinson No32 line-stage preamplifier in my reference system. The No436 is a rack-mountable 350-watt Class AB monaural power amplifier that measures 15.5 inches in width, 20.5 inches in depth and nearly a 4 RU high rack height of six-and-three-quarters inches. Each amplifier weighs 85 lbs. and has a retail price of $6,250.
The importance of the power amplifier is paramount in an A/V system as it is the last link in your electronics chain and the power plant needed to drive your favorite (and often demanding) loudspeakers. It is responsible for taking the low-level signal from either your line stage or A/V preamp, and making it powerful enough to drive your loudspeakers – not a trivial task. Monaural amplifiers can have many sonic benefits over a stereo amplifier. Firstly, a mono amplifier is designed to drive a single speaker. It doesn’t share power supplies and transformers, so they are capable of supplying more instantaneous current to your speakers. Mono amplifiers also eliminate any potential interaction between audio channels. In a multi-channel audio/video system, this becomes an enormous advantage, as you can connect an amplifier to each discrete audio channel.
When selecting a power amplifier, perhaps the most important consideration, other than cost, is the amount of power that your loudspeakers needs to perform at your desired volume. The lower the sensitivity of your loudspeakers are and the larger your room gets, the more power you will need. For instance, my Revel Salons are rated at 86dB SPL (sound pressure level) @ one watt. What this means is that your speakers will need one watt of power to produce 86 dB of sound at one meter. For instance, my Revel Salon’s are rated at 86dB SPL (Sound Pressure Level) @ 1 Watt. What this means is that your speakers will need one watt of power to produce 86 dB of sound at 1 meter. For each 3dB increase you will need double the power. In my case, this calculates to 256 watts of necessary power to rev my Revel Salons to 110dB of SPL, a volume that my system hears during nearly all of my energetic listening sessions. As an audio enthusiast rule, if you can afford the abundance of power, go for it. Power provides more than just volume – it provides sonic control and ease along with system protection. It is much harder to blow drivers with a system that is not distorting – even at high levels.
The Mark Levinson No436 is packaged in a newer, sleeker suit than earlier amps like the Mark Levinson No336 stereo amplifier. With the surge of multi-channel entertainment and the need for more than a single stereo amplifier, the No436 mono amplifier was produced with space savings in mind. Its minimalist package is sized to fit in a rack and take up as little rack space as possible. The front of the chassis has two aesthetically-pleasing silver aluminum wings that are connected to the main black-colored chassis via standoffs. Additionally, the Mark Levinson logo and the power and standby buttons finish off the front panel. At the rear of the amplifier are handles to assist you in moving the amplifier, inputs for both balanced and single ended cables, and a variety of communication connections. Gone are the oversized external heatsinks that once identified a Mark Levinson amplifier, replaced by a much more sophisticated heat exchange/thermal management system. A row of slots perpendicular to the face plate are visible only from the top of the chassis. At lower temperatures, these slots cool the amplifier with natural convection. As the temperature of the amplifier rises, fans draw air through the cross-cut heat sink, which forms an isolated tunnel, thereby preventing dust from being drawn into the amplifier which could ultimately compromise performance and reliability. These thermally controlled fans adjust their speeds based on necessary cooling requirements. Because the fans run at their highest speeds when you are driving the amplifiers the hardest, you are virtually assured that they will never be heard. I could never discern the sound of the fans in my system, whether the amplifiers were operating or idle.
The No436 employs Madrigal’s proprietary Adaptive Biasing Output Stage. This philosophy was originally introduced in the Mark Levinson No33 Reference Monaural Amplifier many years ago and has since found its way into the 300 and 400 series amplifiers. Although all Class AB amplifiers have a biasing stage, Madrigal’s has been designed to greatly extend the amount of available Class A amplification. With the No436, the devices are turned off gradually, eliminating the risk of reverse biasing and allowing for much reduced crossover distortion.
The No436 is a fully balanced design. It utilizes 16 output transistors to control the power flow to the loudspeakers. This provides eight matched sets per amplifier. Internally, the No436 uses pure oxygen-free copper buss bars for power distribution, to alleviate noise and power inconsistencies seen with typical wire harnesses.
For control and automation, the No436 provides a DC trigger input, allowing for external control of its power and standby modes. There are also DC trigger inputs, allowing you to control multiple amplifiers from a single control source. The No436 supplies link-ports for communication and automation between the No436 and other Mark Levinson components.
Additionally, the No436 provides PHAST and RS-232 communication ports for compatibility with other external control systems. The No436 provides several operating stages: Off, Sleep, Standby and On. These pre-listen stages provide a variety of readiness conditions, each with a different level of power consumption. In standby mode, your amplifiers will need minimal warm-up, although they will consume more power than that in the sleep and off modes.