McIntosh MC901: Two Amplifiers in One Monoblock

The McIntosh MC901 Dual Mono Amplifier is a 1-channel power amplifier for high-end Hi-Fi systems and was specially developed for bi-amping loudspeakers. Two different amplifier sections operate on a shared chassis: a 300-watt tube amplifier and a 600-watt transistor amplifier. This allows each amplifier technology to handle precisely the range for which it is intended.

Clear Division of Tasks for Mid/High Frequencies and Low Frequencies

The tube section powers the mid and high-frequency ranges of the loudspeaker, while the transistor section drives the power-intensive woofers. Both sections deliver their full power at 2, 4, or 8 ohms. For a stereo system, two MC901s are required, as one MC901 drives one loudspeaker.

Bi-Amping Without External Crossover

The MC901 features an integrated, adjustable internal crossover. The low-pass filter of the transistor section and the high-pass filter of the tube section can each be adjusted from 100 Hz to 1 kHz. This allows the crossover point to be selected to match the loudspeaker. Additionally, the relative levels of both amplifier sections can be adjusted from -6 dB to +3 dB.

Connections for Flexible Hi-Fi Setups

The MC901 offers balanced and unbalanced inputs for Solid State Direct, Vacuum Tube Direct, and Composite. Composite is the obvious choice if a signal from a preamplifier is to be distributed to both amplifier sections and adjusted via the internal filters. Direct Inputs bypass level adjustment and filters and are suitable for setups with an external crossover or separate signal routing.

Operation and Control Directly on the Device

The device features an input mode switch for balanced or unbalanced inputs, Direct/Composite switch, filter and level controls, and an Auto-Off switch. On the front are the Power Control knob and the Meter Control knob. The DualView™ Power Output Meter displays the power of the tube and transistor sections separately in real-time.

Protection Functions for Amplifiers and Loudspeakers

Power Guard® protects the transistor section from clipping and audible distortion. Power Guard Screen Grid Sensor™ monitors the KT88 output tubes and intervenes if the tubes would operate outside safe operating ranges. Sentry Monitor™ monitors the output current and switches off the amplifier in critical conditions.

Plan for Sufficient Space for Installation

The MC901 weighs 81.6 kg and should be placed upright on the floor or a suitable amplifier stand. For enclosed installation, specific ventilation requirements apply: at least 48.3 cm of free space above, and 15.2 cm at the front, rear, and sides. We therefore recommend reviewing the selection with us to match loudspeakers, installation, and listening room.

Pros and Cons at a Glance

Reasons to choose the McIntosh MC901:

• Combination of 300-watt tube amplifier and 600-watt transistor amplifier
• Specially developed for bi-amping loudspeakers
• Full power at 2, 4, or 8 ohms
• Internal, adjustable crossover from 100 Hz to 1 kHz
• Separate level adjustment for both amplifier sections
• DualView™ Power Output Meter for both amplifier ranges
• Power Guard®, Power Guard SGS™, and Sentry Monitor™ as protection functions

Things to know before buying:

• One MC901 drives one loudspeaker; two units are needed for stereo
• The loudspeaker must be suitable for separate control of the low-frequency and mid/high-frequency sections
• At 81.6 kg, the amplifier requires a very stable installation location

Specifications

General

• Product type: 1-channel power amplifier / Dual-Mono Monoblock
• Amplifier principle: Hybrid Drive with tube and transistor section
• Number of channels: 1
• Dimensions W × H × D: 44.5 × 34 × 75 cm
• Weight: 81.6 kg
• Shipping weight: 90.7 kg

Power

• Transistor section: 600 W into 2, 4 or 8 Ohm
• Tube section: 300 W into 2, 4 or 8 Ohm
• Power band: 20 Hz to 20 kHz

Audio

• Frequency response transistor section: +0, -0.25 dB from 20 Hz to 20 kHz; +0, -3 dB from 10 Hz to 100 kHz
• Frequency response tube section: +0, -0.5 dB from 20 Hz to 20 kHz; +0, -3 dB from 10 Hz to 70 kHz
• Total harmonic distortion transistor section: 0.005 % maximum, 20 Hz to 20 kHz
• Total harmonic distortion tube section: 0.5 % maximum, 20 Hz to 20 kHz
• Signal-to-noise ratio transistor section: 122 dB
• Signal-to-noise ratio tube section: 112 dB
• Dynamic headroom transistor section: 2.5 dB
• Dynamic headroom tube section: 1.2 dB
• Damping factor transistor section: >40
• Damping factor tube section: >18

Circuitry and Output Technology

• Circuitry transistor section: Quad Balanced
• Circuitry tube section: Unity Coupled
• Output transistor section: Autoformer™
• Output tube section: Unity Coupled Circuit Output Transformer
• Mono Bridge: No
• Mono Parallel: No

Tube Complement

• Output tubes: 8 × KT88
• Signal tubes: 4 × 12AT7
• Signal tubes: 2 × 12AX7A

Filter and Level Adjustment

• Low-pass filter transistor section: 100 Hz to 1 kHz
• High-pass filter tube section: 100 Hz to 1 kHz
• Level adjustment per amplifier section: -6 dB to +3 dB

Connections

• Balanced inputs: 3 × Balanced
• Unbalanced inputs: 3 × Unbalanced
• Input sections: 1 × Solid State Direct, 1 × Vacuum Tube Direct, 1 × Composite
• Speaker connections: Solid Cinch™ Speaker Binding Posts
• Speaker outputs transistor section: positive and negative connections for 2, 4 and 8 Ohm
• Speaker outputs tube section: positive and negative connections for 2, 4 and 8 Ohm
• Power Control: In and Out

Operation and Features

• DualView™ Power Output Meter
• Meter-light switch: Yes
• Power Control: Yes
• Auto Off: Shut-off after 30 minutes without input signal, if activated
• Front panel: Glass
• Illumination: Direct LED
• Chassis: polished stainless steel and black painted steel

Power Supply

• Mains voltage variants: 100 V, 110 V, 120 V, 127 V, 220 V, 230 V, 240 V at 50/60 Hz
• Standby: less than 0.5 W

Scope of Delivery

• McIntosh MC901
• Tube protection cage
• Power cord
• Documents

• Broschüre
• Anleitung