McIntosh MC901

Since the 1940s, McIntosh has refined the art of vacuum tube amplifiers and, since the 1960s, solid-state amplifiers. These amplifiers have powered historic moments such as presidential inaugurations and Woodstock, as well as legendary sound systems like the Grateful Dead’s Wall of Sound and Despacio. Drawing from this heritage, McIntosh presents the MC901 Dual Mono Amplifier—a distinctive solution for bi-amping loudspeakers that only McIntosh could envision, design, and create.

The MC901 is a unique monoblock amplifier that powers a single speaker, featuring an innovative design that merges two amplifiers into one chassis. Even more remarkably, these amplifiers employ different design philosophies: a 300 Watt vacuum tube amplifier paired with a 600 Watt solid-state amplifier.

The 300 Watt vacuum tube section powers the midrange and high-frequency drivers using eight KT88 output tubes, along with four 12AT7 and two 12AX7A signal tubes. The 600 Watt solid-state section supplies ample power to the bass drivers. The vacuum tube section utilizes McIntosh’s patented Unity Coupled Circuit output transformer, a cornerstone of the brand since 1949, ensuring the full 300 Watts is delivered into 2, 4, or 8 Ohm loads. Similarly, the solid-state section employs McIntosh’s Autoformer™ technology, providing a full 600 Watts into 2, 4, or 8 Ohm speaker loads.

The MC901’s design ensures optimal performance by having the vacuum tube section handle only the mid and high frequencies, while the solid-state section takes care of the low-end frequencies. This separation prevents the vacuum tubes from amplifying low frequencies, preserving their performance. The two amplifier sections work in harmony, each with its own power supply to maintain independent operation without performance compromises, resulting in seamless bi-amping with superior sound reproduction.

Previously, bi-amping required two separate amplifiers, an external crossover, and significant adjustments to synchronize the components. The MC901 eliminates this complexity with an integrated, adjustable crossover accessible on the top panel. This feature allows users to fine-tune the performance of each section according to their preferences. Gain levels for each amplifier section can be adjusted from -6dB to +3dB, and direct feeds can bypass the filters if desired.

True to McIntosh tradition, the MC901 features the iconic “McIntosh Blue” Watt meter, recognized globally as a symbol of premium audio. This model introduces the DualView Power Output Meter, with two independent mechanical meters in a single display—one for the 300 Watt tube amp and the other for the 600 Watt solid-state amp—showing real-time power output for each section.

Despite being a new concept, the MC901 incorporates advanced McIntosh technology:

• Power Guard in the 600 Watt solid-state section monitors and subtly adjusts the input signal in real-time to prevent distortion and clipping.

• Power Guard Screen Grid Sensor (SGS), a first for McIntosh, in the 300 Watt tube section, monitors screen grid current in the KT88 tubes, dynamically adjusting the input signal to prevent tube strain and premature failure.

• Sentry Monitor circuit shuts down the amplifier if output current surpasses safe thresholds.

• Quad Balanced Design reduces noise and distortion for a pristine audio signal.

• Power Control for synchronized power on/off commands to other connected McIntosh components.

• Solid Cinch speaker binding posts, patented and gold-plated, secure speaker cables and prevent corrosion.

• Monogrammed Heatsinks, linked to advanced high-current transistors, maintain optimal cooling for the solid-state section.

The MC901 exemplifies McIntosh’s dedication to high-end audio innovation and quality.