The McIntosh MC451 combines a 150-watt vacuum-tube amplifier and a 300-watt solid-state amplifier in one monoblock chassis for bi-amplified loudspeakers. The tube section is intended for midrange and high-frequency drivers, while the solid-state section supplies the woofer channel.
An adjustable crossover allows the two amplifier sections to be coordinated around the loudspeaker's requirements. The tube circuit uses four KT88 output tubes, two 12AT7 tubes, and one 12AX7A tube; McIntosh Autoformer and Unity Coupled output technologies provide dedicated 2-, 4-, and 8-ohm connections for the respective sections.
Three Important Features
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Purpose-built bi-amplification: Separate tube and solid-state amplifier sections power different frequency ranges of one loudspeaker.
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Adjustable crossover: The transition between the two amplifier sections can be tailored to the loudspeaker.
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Dual output technologies: Unity Coupled tube output and Autoformer-coupled solid-state output share one chassis.
Three Important Specifications
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Tube complement: Output: four KT88; signal stages: two 12AT7 and one 12AX7A.
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Power output: Tube section: 150 watts; solid-state section: 300 watts, each into 2, 4, or 8 ohms.
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Total harmonic distortion: Tube section: 0.5%; solid-state section: 0.005%.
