McIntosh C2200 Technical Description, Overall Design, Block Diagram of, shown with Power Supply

Technical Description

Logarithmic Attenuator. There are stringent requirements for the Volume Attenuator in this design. The channel to channel tracking accuracy must be maintained. After a great deal of research we found that mechanical potentiometers cannot approach the tracking accuracy that McIntosh felt was necessary. Therefore, we choose to use a dual attenua- tor with switching driven from a 16-bit serial data word. Resistor values are decoded by an internal multiplexer to steps of 0.5dB. Total attenuator range is 107dB. Step error and channel matching is less than .1dB. THD+N is typically less than .001% and dynamic range is 120dB. A second stage is added to the volume attenuator. It controls the gain of the output amplifier. Its steps are interlaced with the main section in such a manner that it reduces the output amplifier gain to unity almost immediately as volume is reduced. Therefore, noise and distortion generated in earlier stages is not amplified and low level S/N is dramatically improved. It is comparable to having a straight wire between the input switching and output connector. Care has been taken to in- sure that there are no audible artifacts in the analog output signal during volume control changes. There is a zero

Side Inside View of the C2200

Bottom Inside View of the C2200

crossing detector built in and all changes in level occur at the signal zero crossing.

Overall Design

The C2200 was designed to use the best components avail- able. All resistors are the lowest noise 1% metal film. Each amplifier section has its own power supply filter. The C2200 is truly worthy of being considered a companion and peer of the world famous MC2000 and MC2102 Tube Power Amplifiers.

Block Diagram of

Preamplifier and Meter Circuitry (one channel

shown) with

Power Supply

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