Introduction

Following on our recent review of the Mark Levinson N^o 326S Preamplifier, we now review the N^o 433 three-channel (200 watts per channel) and N^o 436 (350 watts monoblock) power amplifiers.

The N^o 436 is several years old, while the N^o 433 is new, reflecting the current interest in home theater.

There is also a N^o 431 which is a dual-mono design, with 200 watts per channel output, and a N^o 432, with 400 watts per channel output.

The Design

The N^o 433 has three channels, each rated at 200 watts RMS into 8 ohms. Each channel has its own power supply, using a separate toroidal power transformer and two low ESR power supply capacitors. It is also called a triple-mono design.

Large copper bus bars handle power distribution, and each amplifier channel is fully balanced from input to output. The PC board layout of each leg of the amplifier signal is mirror imaged so as to cancel magnetic fields.

The N^o 433 and N^o 436 share some of the same design characteristics, such as Adaptive Bias (controls the amount of Class A bias) and being fully balanced.

The N^o 436 is, obviously, a much more powerful amplifier. It has a huge toroidal power transformer, rated at 2372 VA (more than 2,000 watts), for its specified 350 watts output into 8 ohms. It also has 80,000 µF of power supply capacitance. So, even at full 700 watt output into 4 ohms, the N^o 436 power supply has several times that value in reserve. This is very unusual in an amplifier design, but routine for Mark Levinson.

Overall, the two amplifiers are about the same size, although the N^o 433 is much heavier due to it having three channels. The first photo below shows an inside view of the N^o 433, and the second photo shows the N^o 436.

 

Both amplifiers get pretty warm (hot actually) during use, indicating their Class A bias to varying degrees.

Power-on is from two buttons on the front panel, and you have four levels: Off, Sleep, Standby, and On. In the Sleep mode, AC is delivered to one small power supply, as well as the communication and control circuits. This lets a signal from other components turn the power amplifier on. In the Standby mode, power is delivered to the main power supply and voltage gain circuits. This keeps the amplifier warmed up for immediate use. In the Sleep mode, you will need to let the amplifier warm up for a half hour or so after turning the amplifier to On, to have it reach its full sound quality potential (Levinson states this, and it was also my experience).

The rear panels of the two amplifiers are shown below, the N^o 433 first and N^o 436 second.

Both panels are simple, with RCA unbalanced and XLR balanced inputs, heavy twist binding posts (they accept bare wire and spade lugs, but not banana plugs), communication jacks, trigger jacks, and a grounded AC socket.

A close-up of the N^o 436 communication panel is illustrated below. The Slave In jack connects to the Slave Out jack of, say, the N^o 326S preamplifier, so that when you turn on the N^o 326S, the N^o 436 then also turns on. The Slave Out jack on the N^o 436 connects to other equipment that you want turned on as well, such as additional N^o 436 amplifiers. You can use the Trigger In jack if you want to turn on the N^o 436 from a non-Levinson component that uses standard 12 volts or 5 volts trigger signals. The N^o 433 also has communication jacks.

Click Here to Go to Part II.