Madrigal Imaging N33, power amplifier manual Special Design Features

Massive Power Supply

AC Regeneration

Special Design Features

Congratulations on your purchase of Mark Levinson Nº33 Reference Monaural Power Amplifiers. While your new amplifiers are straightforward in their everyday use, they include several design features which are responsible for their outstand- ing performance. In particular, the Nº33 Reference Monaural power amplifiers defy the accepted wisdom that it is impossible to design a large, powerful ampli- fier that also has all of the finesse of the finest smaller amplifiers. A few of the technical highlights that make this possible are given below.

The Nº33 incorporates two 2.45 kVA low noise toroidal transformers in a fully balanced power supply. In this design, there is a separate power supply (each with its own power transformer) for both the inverting and non-inverting halves of the amplifier. Twelve 39,000 ∝ F low ESR capacitors are used in each amplifier. The power supply of each Nº33 provides almost 1⁄2 a Farad of capacitance and 1200 Joules of energy storage.

Heavy oxygen-free copper bus bars enhance the efficiency of power distribution within the amplifier and eliminate variances introduced by the wiring harnesses, etc. more commonly found even in high performance amplifiers. High frequency power supply bypass is accomplished on individual PC boards by a total of 56 components of several film types. The resulting uniformly low power supply im- pedance seen by the various circuits within the Nº33 lays the foundation for both the massive power and the extraordinary finesse that characterizes this amplifier.

In recent years, the detrimental sonic effects of noisy, unbalanced AC mains sup- plies have become widely known. Various passive AC “line conditioners” are avail- able for use with line level components such as preamplifiers and digital audio processors to address these problems. In most cases, these line conditioners pro- vide some filtering of the AC mains, along with some measure of surge protec- tion. None of these devices may be used to good effect with power amplifiers, however, since they cannot handle the large instantaneous currents which power amplifiers require during normal operation. In effect, passive line conditioners become a “bottleneck” in the otherwise free flow of power through the amplifier to the speakers, reducing dynamic impact and musicality.

In the Nº33, a more sophisticated approach is used that provides greater line con- ditioning benefits than the commercially available passive devices can hope to provide, while simultaneously avoiding any performance “bottlenecks.”

A distortion-free 60 Hz sinewave is regenerated within the Nº33, and then used to power a separate power supply dedicated to all the voltage gain stages. AC power is delivered from the wall to the primary supply of the Nº33, where it is rectified, filtered and regulated into positive and negative DC voltages. A portion of this DC power is then used to drive an oscillator circuit which regenerates a pure 60 Hz sinewave without any of the noise or contamination so common to the AC mains as delivered to our homes by power utilities.

The regenerated, pure sinusoidal AC wave is then sent to a dedicated secondary power supply, where it is converted to positive and negative DC power to be used by all of the voltage gain stages. This dedicated supply for voltage gain stages benefits from having a truly balanced source (unlike the dissimilar imped-

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