Source: Press Release, Last Accessed: 2019/12/11

The MC901 is a monoblock amplifier that drives a single loudspeaker. But it is unique in that it's two amplifiers combined into one: Each chassis consists of a 300 Watt vacuum tube amplifier and a 600 Watt solid state amplifier, to drive the mid/high and the low frequency part of the loudspeaker respectively.
The 300 Watt vacuum tube portion powers the speaker's mid and upper drivers via eight KT88 output tubes, plus four 12AT7 and two 12AX7A signal tubes; the solid state section delivers 600 Watts of dedicated power to the power hungry woofers. The 300 Watt vacuum tube amp in the MC901 uses McIntosh's patented Unity Coupled Circuit output transformer – the same technology McIntosh was founded on in 1949 – to deliver its full 300 Watts into almost any speaker regardless if it has 2, 4 or 8 Ohm impedance. Similarly, the 600 Watt solid state amp delivers its full 600 Watts into a 2, 4 or 8 Ohm impedance speaker via McIntosh's Autoformer technology.
Prior to the MC901, bi-amping a speaker required two separate amplifiers. It also required an external crossover, along with a lot of trial and error, to properly configure the two detached amplifiers so they worked together as best as possible. The MC901 solves this issue thanks to its internal, adjustable crossover with the controls easily accessible on the top of the unit. These adjustable crossover filters allow the user to optimize the performance of both amplifier sections to their listening preferences. Relative gain levels for each amplifier section can be adjusted from -6dB to + 3dB. A direct feed can also be connected to each amplifier section, thus bypassing the filters.
The iconic "McIntosh Blue" Watt meter is upgraded to McIntosh's new DualView Power Output Meter, featuring two of McIntosh's traditional, fast responding mechanical meters stacked in a single meter window; one meter is dedicated to the 300 Watt vacuum tube amp and the other to the 600 Watt solid state amp.
The MC901 comes with the technologies one would expect from a McIntosh amplifier: Power Guard in the 600 Watt solid state amplifier section, Sentry Monitor, Quad Balanced design, Power Control, Solid Cinch speaker binding posts, McIntosh Monogrammed Heatsinks, and McIntosh's eco-friendly Power Management System. A brand new technology in the 300 Watt vacuum tube amplifier section of the MC901 is Power Guard Screen Grid Sensor (SGS). Power Guard SGS helps prevent premature vacuum tube failure by monitoring the screen grid current in the KT88 output vacuum tubes.

For more information: https://www.mcintoshlabs.com/

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