McIntosh MC1201 monoblock power amplifier Manufacturer's Comment
Editor: The following bullets are comments on the technical section of the review, starting at the beginning of the "Measurements" section.
• The output stage is listed as class-B. It is actually a class-A/B output stage.
• A comment about the 40-minute operation at 1/3 power: This is done to keep the top cover of the amplifier from exceeding 65 degrees C, which is a requirement for CE certification. The unit is designed using parts that are safely operated at 80 degrees C and higher. Allowing the unit to shut down at 65 degrees C is extending the life of the product. The only music material that is really available today that is compressed enough to represent 1/3 power would perhaps be an FM radio station (if you could imagine listening to 400W continuous). It is reported that the amplifier needed to be reset when this occurred—the reset is automatic. Once the amplifier overheats, it mutes the input; after it cools down, it then unmutes automatically. There is no reset required by the user.
• The comment about the Grateful Dead using McIntosh amps: These amps were the MC2300s, which were forced-air-cooled. Physically they were the same size as the MC1201, but with a total output of only 600W.
• In reference to figs.8, 9, and 10: I would like to question the consistency in the 2 ohm load measurements in these graphs—especially fig.10, where the impedance is matched to the 2 ohm tap. Without knowing the exact test conditions or type of load that was used, in my experience in measuring the 2 ohm tap, the connection of the load can be extremely critical—especially in its mechanical integrity. I have seen this type of irregularity on the bench here when the connection is lacking in mechanical integrity. Each of the graphs seemed to show a consistent distortion response, except for the 2 ohm, which would lead me to believe that there is something not consistent with the 2 ohm test setup.
Here at the factory, each amplifier tap is checked, loaded with its respective impedance on the production line, and has to pass at 0.005% THD—as did the amplifier that was reviewed. This test is done from 20Hz to 20kHz at 1200W and at 12W.—Charlie Randall, McIntosh Laboratory