MCINTOSH MC451

Pre owned. In good condition. Shows light signs of wear. Original packaging not included.

The McIntosh MC451 is a monophonic power amplifier designed to deliver reference-level performance through the proprietary patented Hybrid Drive technology, which coherently combines the sonic character of vacuum tubes with the power, control, and stability of solid-state amplification. Its exclusive Dual Monoblock architecture integrates two completely separate and independent amplification sections within a single chassis, each optimized to operate over different frequency ranges and conceived for advanced, precise, and easy-to-configure bi-amplification.

The vacuum tube section of the MC451 is dedicated to the reproduction of mid and high frequencies and delivers 150 continuous watts into 2, 4, and 8 ohm loads thanks to Unity Coupled output transformers. It is equipped with four KT88 power tubes and three signal tubes—two 12AT7 and one 12AX7A—capable of providing a natural, rich, and three-dimensional tonal character. The solid-state section, designed to drive low frequencies, supplies 300 watts into 2, 4, and 8 ohms via Autoformer technology and uses high-current Onsemi ThermalTrak power transistors, ensuring control, dynamics, and depth even with the most demanding woofers.

The MC451 incorporates a variable crossover that allows precise adaptation of frequency distribution to the characteristics of the connected loudspeaker. The crossover point can be selected from nine values between 100 Hz and 1 kHz, while the level of the vacuum tube section can be adjusted in five steps from -6 dB to +3 dB, enabling extremely accurate fine-tuning according to listening preferences. The amplifier can operate in Mono mode, where the input signal is sent to the internal crossover, divided, and routed to the two amplification sections, or in Separate mode, where the full-range signal is sent unchanged directly to the tube and solid-state stages, even simultaneously, allowing the amplifier to drive two independent pairs of loudspeakers or to completely bypass the internal crossover.

Connectivity includes balanced XLR and unbalanced RCA inputs dedicated to each amplification section, ensuring maximum flexibility when integrating into any high-end audio system. The front panel features the DualView Power Output Meter, with two independent mechanical VU meters—one for each amplifier—housed in a single window with Direct LED backlighting. Heat dissipation is handled by the characteristic McIntosh Monogrammed Heatsinks, shaped with the Mc logo and designed to provide high thermal efficiency and optimal sonic performance from power-up.

The MC451 also integrates proprietary Power Guard and Sentry Monitor protection systems, which safeguard loudspeakers by preventing clipping and protecting the amplifier from overloads and short circuits, complemented by Power Guard Screen Grid Sensor technology that monitors and compensates in real time for any abnormal currents on the tube grids. Additional features include a defeatable Auto-Off function and Power Control input and output connectors for integration with other McIntosh components. The result is an amplifier capable of bringing out the very best in high-end loudspeakers, delivering powerful, refined, and perfectly controlled sound across the entire frequency range.

Technical Specifications:

• Rated FTC power output: solid-state section 300 W; vacuum tube section 150 W
• Power output per channel: solid-state section 300 W into 2, 4, or 8 ohms; vacuum tube section 150 W into 2, 4, or 8 ohms
• Number of channels: 1
• Total harmonic distortion: solid-state section 0.005% maximum from 250 mW to rated power, 20 Hz–20 kHz; vacuum tube section 0.5% maximum from 250 mW to rated power, 20 Hz–20 kHz
• Signal-to-noise ratio below rated output: solid-state section 118 dB; vacuum tube section 112 dB
• Dynamic headroom: solid-state section 2.5 dB; vacuum tube section 1.2 dB
• Damping factor: solid-state section >40; vacuum tube section >18
• Rated power bandwidth: solid-state section 20 Hz–20 kHz; vacuum tube section 20 Hz–20 kHz
• Frequency response: solid-state section +0/-0.25 dB from 20 Hz to 20 kHz, +0/-3 dB from 10 Hz to 100 kHz; vacuum tube section +0/-0.5 dB from 20 Hz to 20 kHz, +0/-3 dB from 10 Hz to 70 kHz
• Remote power control: yes
• Speaker terminals: patented Solid Cinch™ binding posts
• Circuit configuration: solid-state section push-pull complementary; vacuum tube section Unity Coupled
• Circuit design: solid-state and vacuum tube
• Output type: solid-state section Autoformer™; vacuum tube section Unity Coupled output transformer
• Meters: DualView™ Power Output Meter
• Meter light switch: yes
• Balanced inputs: 2, including 1 for solid-state or mono and 1 for vacuum tube
• Front panel: glass
• Illumination: Direct LED
• Chassis construction: polished stainless steel and black painted steel
• Dimensions (W × H × D): 45.4 × 30 × 54.6 cm
• Weight: 60.3 kg