Technical Description

McIntosh Laboratory, the company who introduced the world’s first amplifier that could be called “High Fidelity”, has done it again. The McIntosh engineering staff has cre- ated a power amplifier without compromise, using the most advanced McIntosh circuit design concepts.

A continuous average power output rating of 400 watts and with an output current of greater than 100 amperes per channel, makes this not only the most advanced, but also one of the most powerful amplifiers McIntosh has ever manufactured. The distortion limits for the MC402 are no more than 0.005% at rated power output for all frequencies from 20Hz to 20,000Hz. Typical performance at mid fre- quencies is less than 0.002%. The true distortion readings on the MC402 are so low, it takes special measuring tech- niques to make accurate readings. The MC402 can deliver the best possible performance from any type of high qual- ity Loudspeaker system.

Creating an amplifier with this level of performance did not come easily. Many months of design, testing and mea- suring were required. Extensive controlled listening tests, the ultimate form of measuring, were made before the final design was accepted.

Design Philosophy

The design philosophy incorporated in the MC402 in- volved several different techniques, all based on sound sci- entific logic. Every stage of voltage or current amplifica- tion must be as linear as possible prior to the use of nega-

tive feedback. McIntosh engineers know how to properly design negative feedback circuits so they contribute to the extremely low distortion performance expected from a McIntosh amplifier. The typical McIntosh owner would never accept the approximately 100 times higher distortion of many non-feedback designs.

Double Balanced Push-Pull design is used from input to output. Each half of the amplifier contains complimentary balanced circuitry. The resulting double balanced configu- ration cancels even order distortion. Refer to figure 20.

All transistors are selected to have nearly constant cur- rent gain over the entire current range they must cover. Output transistors in particular, have matched uniform cur- rent gain, high current bandwidth product and large active region safe operating area. An automatic tracking bias sys- tem completely eliminates any trace of crossover distor- tion. Precision metal film resistors and low dielectric ab- sorption film capacitors are used in all critical circuit loca- tions.

The output signals of the balanced circuit are coupled in the unique McIntosh MC402 Output Autoformer. It pro- vides low distortion power transfer at frequencies from be- low 20Hz to well beyond 20,000Hz with optimum imped- ance points of two ohms, four ohms and eight ohms. The unequaled expertise of McIntosh in the design and manu- facturing of autoformers is legendary in the high fidelity industry.

The high efficiency circuit design of the MC402 con-

Block Diagram

of the

Amplifier and Meter Circuitry

Figure 20

MC402 specifications

The McIntosh MC402 is a powerful and elegant amplifier that represents the pinnacle of high-fidelity audio performance. This two-channel amplifier stands out in the McIntosh lineup, delivering a robust 400 watts per channel into 2, 4, or 8-ohm loads. It is designed for audiophiles who seek uncompromising sound quality and superior performance, making it an ideal choice for both home studios and high-end listening rooms.

One of the standout features of the MC402 is its unique Autoformer technology, which allows the amplifier to deliver the same power output irrespective of the speaker impedance. This feature ensures that users enjoy consistent performance whether they are using 2-ohm, 4-ohm, or 8-ohm speakers. The use of transformers is integral to maintaining fidelity and output power while providing an additional layer of protection for the amplifier and connected speakers.

Additionally, the MC402 employs a quad balanced circuit design, which helps to eliminate distortion and achieve greater clarity in sound reproduction. This approach ensures that the audio signal remains pure from input to output, allowing listeners to experience their music in the way it was intended to be heard. The dual-construction design of the amplifier not only enhances its aesthetic appeal with the classic McIntosh blue meters and sleek black glass front but also contributes to its durability and reliability over time.

The amplifier features a robust cooling system that includes large heat sinks to dissipate heat effectively, ensuring optimal performance even during prolonged listening sessions at high power levels. This aspect of its design guarantees that the MC402 maintains a consistent performance without overheating.

In terms of connectivity, the MC402 is versatile, featuring balanced and unbalanced inputs to accommodate a variety of audio sources. The amplifier also has a signal sensing circuit that automatically turns it on when an audio signal is detected and powers it down when the signal is absent, helping conserve energy and adding convenience for users.

Overall, the McIntosh MC402 amplifier combines cutting-edge technology with timeless design. Its impressive power output, advanced circuitry, and robust construction make it a top choice for those who demand the best in audio performance. Whether driving efficient speakers or high-power systems, the MC402 is engineered to elevate your listening experience to new heights.