McIntosh MC451 AC Dual Mono Amplifier

MC451 amplifier

The MC451 AC builds on the success of the McIntosh MC901 model with the finest technical sophistication and offers a combination of valve and solid state amplifier that uses the exclusive "Hybrid Drive" technology. As the smaller brother of the MC901, the McIntosh MC451 shares the same layout but is twice as powerful.

BREATHTAKING SOUND EXPERIENCE

The McIntosh Dual Mono Amplifier works with the MC901 to provide the ultimate solution for bi-amping a loudspeaker. It uses Hybrid Drive technology, which combines a separate tube and solid state amplifier in one package to deliver the best possible sonic performance in a conventional McIntosh form factor and size.

DUAL MONO AMPLIFIER

- Contains our Hybrid Drive™ technology, which combines the best of tube and
uses solid state amplifiers to achieve the best sound performance

- Designed for bi-amp operation of speakers

- 150 watt vacuum tube amp and 300 watt solid state amp in one box

- Vacuum tube section drives midrange and tweeter

- Solid-state section drives power-hungry woofers

- DualView™ output power meter

The MC451 consists of a 150 watt vacuum tube amplifier and a 300 watt solid state amplifier, which is more than enough power to drive virtually any speaker.

The tube amp drives the speaker's midrange and tweeters, while the solid-state amp drives the woofers. The 150 watt vacuum tube amp is powered by four KT88 output tubes housed under a removable wire cage, plus two 12AT7 and one 12AX7A signal tubes; it uses our patented Unity Coupled Circuit output transformer to deliver the full 150 watts to almost any speaker, whether it has an impedance of 2, 4 or 8 ohms.

Similarly, the 300 watt solid state amplifier delivers the full 300 watts of power into a 2, 4 or 8 ohm speaker via our Autoformer™ technology.

The two amplifiers in the MC451 are designed to work together in a synergistic relationship and have been specifically engineered to ensure that each only amplifies the frequencies it is designed for. The large but quiet toroidal transformer produces so much power that neither amp steals power or performance from the other. All this results in simple bi-amping with unparalleled performance and sound reproduction from your speakers.

Bi-amping your speakers with the MC451 is easy. You no longer have to fiddle with two separate amplifiers, an external crossover, and a lot of trial and error to properly configure the two separate amplifiers, which often yields only mediocre results. The MC451 solves these problems thanks to its internal, adjustable crossover. The MC451's crossover adapts the output frequency range of the individual amplifier sections to the loudspeaker connected. Simply set the CROSSOVER POINT control on the rear of the MC451 to match the loudspeaker's crossover point, then frequencies below the crossover point will be sent to the solid state amplifier and frequencies above the crossover point will be sent to the tube amplifier.

This adjustable crossover allows you to optimize the performance of the two amplifier sections according to the specifications of your speaker and your listening preferences. The gain level for the tube amp can be adjusted from -6dB to +3dB. A direct feed can also be connected to each amplifier section, bypassing the internal crossover.

The MC451 features our DualView™ Power Output Meter. The DualView gauge features two of our traditional, fast-acting mechanical gauges arranged one above and one below the other in a single gauge window; one meter is for the 150 watt tube amp and the other for the 300 watt solid state amp. Each meter works independently of the other and displays the performance values of the individual amplifier sections in real time.

In addition to everything already mentioned, the MC451 features a variety of other McIntosh amplifier technologies:

- Power Guard®, which monitors and adjusts the input signal in real-time in the 300-watt amplifier section, then makes unobtrusive volume adjustments to prevent harsh-sounding distortion and potentially speaker-damaging clipping.

- Power Guard Screen Grid Sensor® (SGS). The 150 watt vacuum tube amplifier section features our Power Guard SGS® technology. Power Guard SGS prevents premature vacuum tube failure by monitoring the screen grid current in the KT88 output tubes. When the current gets too high, a circuit in Power Guard SGS is activated which then dynamically attenuates the input signal in real time to keep the tubes at safe levels.

- Sentry Monitor™ monitors the output current and shuts down the amplifier if it exceeds safety limits.

- Power Control which can send on/off signals to other connected McIntosh Components to facilitate turning the system on and off.

- Our patented, gold-plated Solid Cinch™ speaker terminals for easy and secure connection of speaker cables.

- A McIntosh Monogrammed Heatsink™ mated to advanced high-current output transistors to efficiently cool the solid-state amplifier section.

- Our Power Management System, which turns off the entire device after a specified time if no input signal is detected.

The MC451's uncompromising fit and finish is highlighted by well-known McIntosh design cues. The front features the signature black glass front with three clear windows that allow a view of the vacuum tubes, the DualView meter, two rotary knobs, an illuminated logo and lettering, and integrated aluminum handles. The top is highlighted by a series of block diagrams printed on glass inserts explaining the device's circuitry and specifications. All of this is housed on a stainless steel case that has been polished to a mirror finish.

ELECTRONIC SPECIFICATIONS

output power per channel

Solid state section: 300 watts into 2, 4 or 8 ohms

Vacuum tube section: 150 watts at 2, 4 or 8 ohms

Number of channels: 1

OVERALL HARMONIC DISTORTION

Solid State Section: 0.005% maximum harmonic distortion at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz

Vacuum tube section: 0.5% maximum harmonic distortion at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz

S/N below rated power

Solid state section: 118dB

Vacuum tube section: 112dB

Dynamic headroom

Solid State Section: 2.5dB

Vacuum tube section: 1.2dB

damping factor

Solid State Section: >40

Vacuum tube part: >18

rated power band

Semiconductor range: 20Hz to 20kHz

Vacuum tube section: 20Hz to 20kHz

frequency response

solid section:

+0, -0.25dB from 20Hz to 20,000Hz

+0, -3dB from 10Hz to 100,000Hz

Vacuum tube section:

+0, -0.5dB from 20Hz to 20,000Hz

+0, -3dB from 10Hz to 70,000Hz

STEERING

Remote Power Control: Yes

Multi-channel DB25 cable: KA

CONNECTIVITY

Type of speaker terminals:

Patented Solid Cinch™ speaker binding posts

GENERAL SPECIFICATIONS

circuit configuration

Solid state section: push-pull complementary

Vacuum Tube Section: Unit Coupled

Circuit design: solid state and vacuum tube

Mono Bridge: None

Mono Parallel: None

Output Type: Solid State Section: Autoformer™

Vacuum Tube Section: Unit Coupled Output Transformer

Meters: DualView™ power meter

Gauge Light Switch: Yes

Balanced input: 2 (1 solid state or mono, 1 vacuum tube)

Front panel: glass

Lighting: Direct LED

Case Style: Polished Stainless Steel & Black Lacquered Steel

WEIGHTS AND DIMENSIONS

Unit Dimensions (W x H x D)

17-7/8' (45.4cm) x 11-13/16' (30cm) x 21-1/2' (54.6cm)

Unit weight: 133 lbs (60.3 kg)

Shipping weight: 159 lbs (72.1 kg)