McIntosh MC275 2-Channel Vacuum Tube Power Amplifier

75 Wpc stereo tube amplifier with Unity Coupled output transformers and 150 W monoblock operation

The McIntosh MC275 is one of the company’s longest-running and most recognizable vacuum tube power amplifiers. Originally introduced in 1961, the current sixth-generation version preserves the basic architecture and exposed-tube layout of the original while incorporating modern protection, connectivity, and component refinements.

In stereo operation, the MC275 delivers 75 Wpc into 4-, 8-, or 16-ohm loudspeakers. Its two channels can also be combined for 150 W monoblock operation into 2-, 4-, or 8-ohm loads. McIntosh’s Unity Coupled Circuit output transformers allow the amplifier to deliver full rated power across those supported impedances rather than limiting maximum output to a single nominal load.

Four KT88 output tubes provide the power, while four 12AT7 and three 12AX7A tubes handle the input, voltage-amplification, phase-inverter, and driver stages. The small-signal tubes are LED illuminated to indicate operating status: they glow amber during startup, turn green when the amplifier is ready, and can indicate an output-tube fault by turning red.

Balanced and unbalanced inputs provide compatibility with a wide range of preamplifiers, while Sentry Monitor protects the output stage against unsafe operating conditions without relying on conventional fuses. McIntosh Solid Cinch speaker binding posts, Power Control input and output, and a polished stainless-steel chassis complete an amplifier that remains closely tied to the company’s classic tube designs.

Features

75 Wpc Stereo Operation

The MC275 delivers 75 Wpc into 4-, 8-, or 16-ohm loudspeakers, with both channels operating across the full 20 Hz–20 kHz rated power band.

150 W Monoblock Operation

The two channels can be combined for 150 W mono operation into 2-, 4-, or 8-ohm loudspeaker loads when additional output is required.

Unity Coupled Circuit

McIntosh’s Unity Coupled Circuit output transformer technology allows the MC275 to deliver its full rated output into multiple loudspeaker impedances while maintaining low distortion and wide bandwidth.

All-Tube Signal Path

Four KT88 output tubes are joined by four 12AT7 and three 12AX7A small-signal tubes for an entirely vacuum tube amplification circuit.

Tube Status Illumination

The seven small-signal tubes are LED illuminated to show amplifier status. Amber illumination indicates startup, green indicates normal operation, and red can identify a fault associated with an output tube.

Sentry Monitor

Sentry Monitor provides fuse-less protection for the output stage, shutting the amplifier down if operating conditions become unsafe and automatically restoring operation when conditions return to normal.

Balanced and Unbalanced Inputs

Both balanced and unbalanced inputs are provided, allowing the MC275 to integrate easily with a wide variety of contemporary and vintage preamplifiers.

Solid Cinch Speaker Binding Posts

McIntosh Solid Cinch speaker binding posts provide secure, gold-plated connections for speaker cables and support the amplifier’s dedicated output impedance taps.

Power Control

Power Control input and output connections allow the MC275 to power on and off in coordination with compatible McIntosh components.

What’s Included

• McIntosh MC275 2-Channel Vacuum Tube Power Amplifier
• Tube protection cage
• AC power cord

Specifications

Type: Vacuum tube stereo power amplifier

Channels: 2

Power Output: 75 Wpc into 4, 8, or 16 ohms; 150 W mono into 2, 4, or 8 ohms

Rated Power Band: 20 Hz–20 kHz

Frequency Response: 20 Hz–20 kHz, +0/–0.5 dB; 10 Hz–100 kHz (+0/–3 dB)

Total Harmonic Distortion: 0.5% maximum, 250 mW to rated power, 20 Hz–20 kHz

Intermodulation Distortion: 0.5% maximum

Signal-to-Noise Ratio: 105 dB below rated output, A-weighted

Dynamic Headroom: 1.2 dB

Damping Factor: Greater than 22

Input Sensitivity: 3.4 V balanced; 1.7 V unbalanced

Input Impedance: 20 kΩ balanced; 47 kΩ unbalanced

Vacuum Tubes: 4 × KT88/6550, 4 × 12AT7, 3 × 12AX7A

Circuit Configuration: Unity Coupled

Output Type: Unity Coupled output transformer

Balanced Inputs: 1 stereo pair

Unbalanced Inputs: 1 stereo pair

Mono Operation: Parallel, 150 W into 2, 4, or 8 ohms

Remote Power Control: Input and output

Output Meters: No

Speaker Connections: Solid Cinch speaker binding posts

Illumination: LED-illuminated small-signal tubes

Chassis: Polished stainless steel

Standby Power Consumption: Less than 0.3 W

Dimensions (H × W × D): 8-1/2" × 16-1/2" × 12" (21.6 × 41.9 × 30.5 cm)

Weight: 67 lb. (30.5 kg)