Mark levinson no 32 brochure
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Nº32 REFERENCE PREAMPLIFIER The Nº32 Preamplifier is a revolutionary Mark Levinson component. It is the first preamplifier to earn the Reference label. Separating power-supply and control circuit- ry makes sense in a modern, Reference-level preamplifier. AC power supplies, microprocessors, LED displays - essentially, anything that gener- ates noise - are housed in a separate chassis from the low-level audio signals (the Nº32 Reference Controller), while all of the audio-preamplifier circuitry is housed outboard (the Nº32 Reference Preamplifier). Thus, the audio circuits are exposed only to quiet, regulated DC power and the audio signal itself. Two master power supplies are located in the center section of the Reference Controller: one is dedicated to control and communications; the other is used for the audio circuits. The power from the AC line is pre-filtered, and the two master supplies are isolated from one another. The power supplies use custom-designed transformers featuring multiple secondary windings, which substantially improve isolation between separate circuit blocks. Separate rectification, filtering, and regulation circuits are used to supply DC to the control/communications circuits, a Nº25 phono DC supply output, and the 400Hz oscillator circuits used in power-supply regeneration.The Nº32 employs AC power regeneration: the DC supply feeding the voltage gain stages is derived from an AC source generated within the amplifier itself. This technique is expensive but very effective. In the Nº32 Reference Controller, a 400Hz oscillator generates the AC source for the preamplifiers audio power. Microprocessors are noisy devices which can pollute low-level audio signals if care is not taken to keep processing noise out of the signal path. For this reason, the microprocessors in the Nº32 are not only located in the controller box, physically separated from the preamplifier chassis, but are also within their own shielded box. The microprocessors in the Nº32 control volume changes, signal routing, and other switch- ing functions. They make it easy to name inputs, select mono modes, set mute level, or program offset or gain levels for individual inputs - all from the front panel. Like other current Mark Levinson components, the Nº32 uses a software- based operating system that can be upgraded through its RS-232 port. The Reference Preamplifier chassis has no buttons or knobs. The Reference Controller is used to execute all commands through its simple front panel. Each source can be named in the display, and full control of all functions, with the addition of mono/stereo selection and polarity control, is available from the remote. The Nº32s casework is extraordinary even by Mark Levinson standards, and, like the other aspects of its design, reflects an uncompromising 2
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approach. Its chassis is a custom aluminum casting, machined and finished with a conductive Irridite (clear chromate) coating. This design approach assures a rigid, stable environment in which vibration and microphonic effects are controlled. The left and right channels are separated by a solid aluminum divider wall, formed as part of the casting. Each channel is thus sealed into its own environment to prevent the electromagnetic noise of one channel from degrading the other. Because each channel is effectively isolated from the other electrically and physically, the Nº32s stereo separation is equivalent to that of two sepa- rate mono preamplifiers. The Nº32 is the first Mark Levinson product to use Arlon 25N ®for its circuit boards. This materials superb dielectric properties help the Nº32 achieve remarkable performance with complex audio signals. Arlon 25N was chosenonly after extensive listening tests revealed that it was audibly superior to all other materials in this particular application. Both balanced and single-ended inputs are provided on the rear panel. Single-ended signals have common-mode noise (noise present on both signal and ground) rejected at the input stage. Fully balanced instrumentation amplifiers are employed as the gain stages, and each input can be separately adjusted using the software to offer 0, 6, 12 or 18dB of gain. Using this feature, the Nº32 allows the volume control to work in its optimum range even when its sources have substantially different output levels. While volume control is one of the primary functions of a preamplifier, it is also a source of compromise in many designs. The Nº32 introduces a new active attenuator: a discrete design that offers an unprecedented combination of precision and neutral sonic performance. The 3