Усилители мощности моно — McIntosh MC451

The McIntosh MC451 is a one-channel amplifier that houses two separate amplifiers on one chassis - a solid state section and a vacuum tube section - which McIntosh calls a dual mono design. It went on sale in the US and Canada in December 2022 at USD 14,000, with other markets following shortly after, and was conceived as a more compact follow-up to the MC901, which uses the same Hybrid Drive idea. It now appears among McIntosh's retired models, with limited stock.

Key specs that matter

The solid state section is rated at 300 W into 2, 4 or 8 ohms, while the tube section delivers 150 W into the same three loads. Maximum distortion is 0.005% for the transistor side and 0.5% for the tube side, and signal-to-noise figures are 118 dB and 112 dB respectively. McIntosh gives a damping factor above 40 for the solid state amplifier and above 18 for the tube amplifier, with both sections specified from 20 Hz to 20 kHz. The cabinet measures 454 mm wide, 300 mm high and 546 mm deep, and the unit weighs 60.3 kg, or about 72 kg when shipped.

Engineering and use context

Each half keeps its own output coupling. The transistor stage drives the speaker through a McIntosh Autoformer, and the tube stage uses the patented Unity Coupled Circuit output transformer. Four KT88 output tubes do the power work in the valve section, supported by two 12AT7 signal tubes and one 12AX7A. Two balanced inputs are fitted - one feeds the solid state or combined mono path, the other feeds the tube section alone - so a single signal can drive both halves or each can receive its own feed. Both sections have output taps for all three load impedances, and speaker cables attach to patented Solid Cinch binding posts. A built-in crossover is set with a single knob for crossover frequency, and a second knob sets the balance between the solid state and tube sections. Power Guard, Power Guard SGS and Sentry Monitor provide protection, the driver tubes are illuminated, and Monogrammed Heatsinks cool the transistor stage. On the front, a DualView power output meter stacks two independent mechanical meters vertically, one for each amplifier, so the load on each section can be read at a glance.

Pairing

The MC451 is aimed at bi-amping a single loudspeaker - the solid state side on the woofer terminals and the valve side on the upper section - which needs a speaker with separate bass and treble inputs. A stereo system requires two units, and the balanced inputs call for a preamplifier with XLR outputs, ideally with two balanced pairs so both halves of each amplifier can be fed.

Alternatives

The McIntosh MC901 follows the same hybrid dual mono idea at a higher scale, pairing a 600 W solid state section with a larger tube section driven by eight KT88 tubes.