The McIntosh MC901 combines a 300-watt vacuum-tube amplifier and a 600-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 coordinates the two amplifier sections around the loudspeaker. The tube circuit uses eight KT88 output tubes, four 12AT7 tubes, and two 12AX7A tubes, while Unity Coupled and Autoformer 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 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: eight KT88; signal stages: four 12AT7 and two 12AX7A.
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Power output: Tube section: 300 watts; solid-state section: 600 watts, each into 2, 4, or 8 ohms.
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Total harmonic distortion: Tube section: 0.5%; solid-state section: 0.005%.
