McIntosh MC3500 Mk II: 350-Watt Vacuum Tube Monoblock Amplifier
The McIntosh MC3500 Mk II is a 1-channel vacuum tube power amplifier rated at 350 watts into 2, 4, or 8 ohms. Inspired by the original MC3500 amplifiers used to power the sound system at Woodstock, the Mk II combines the model’s distinctive industrial design with modern McIntosh tube-amplifier engineering, protection systems, and connectivity.
Each MC3500 Mk II powers one loudspeaker channel, so a conventional two-channel stereo system requires two amplifiers. Its Unity Coupled Circuit output transformer allows the full rated output to be delivered across common loudspeaker impedances, making this high-power tube monoblock suitable for demanding full-range speakers and large listening rooms.
Why Choose the McIntosh MC3500 Mk II?
- 350-watt monoblock output: Delivers 350 watts into 2, 4, or 8 ohms from a single amplifier channel.
- High-power vacuum tube design: Uses eight EL509S output tubes selected for their durability and high peak-current capability.
- Fully balanced driver section: Three 12AX7A tubes and one 12AT7 tube handle the input, buffer, voltage-amplification, and output-driver stages.
- Unity Coupled Circuit: McIntosh’s output-transformer design helps provide full rated power across different speaker impedances.
- Power Guard Screen Grid Sensor™: Monitors output-tube screen-grid current and dynamically reduces the input signal when necessary to help protect the tubes.
- Sentry Monitor™: Shuts the amplifier down if output current exceeds safe operating limits.
- Flexible connections: Balanced and unbalanced inputs and outputs support conventional systems as well as bi-amplified and tri-amplified configurations.
- DualView™ power meter: Displays output power and amplifier warmup progress from the center of the front panel.
Who Is the MC3500 Mk II Best Suited For?
The MC3500 Mk II is intended for listeners who want the scale and authority of a very high-powered amplifier while retaining an all-tube signal path. Its 350-watt rating makes it appropriate for large rooms, full-range loudspeakers, lower-sensitivity designs, and systems expected to reproduce wide dynamic swings without giving up the presentation associated with McIntosh vacuum tube amplification.
Because each amplifier weighs 121 pounds and generates substantial heat, installation planning matters. The supporting furniture or amplifier stands should be rated for the weight of a stereo pair, and the tubes require adequate open ventilation above and around the chassis.
McIntosh MC3500 Mk II vs. MC275
The MC3500 Mk II and McIntosh MC275 are both Unity Coupled vacuum tube amplifiers, but they address very different systems. The MC275 delivers 75 watts per channel in stereo or 150 watts when configured as a monoblock. The MC3500 Mk II is a dedicated monoblock that supplies 350 watts to one channel and requires two units for stereo playback.
The MC275 is the more compact and flexible choice for efficient speakers and moderate-size rooms. The MC3500 Mk II is designed for systems requiring far greater output, dynamic headroom, and loudspeaker control. Explore the complete McIntosh power amplifier collection for additional solid state, tube, and hybrid options.
McIntosh MC3500 Mk II Specifications
| Specification | MC3500 Mk II |
|---|---|
| Channels | 1 |
| Power Output | 350 watts into 2, 4, or 8 ohms |
| Circuit Configuration | Unity Coupled |
| Circuit Design | Vacuum tube |
| Output Tubes | 8 × EL509S |
| Driver Tubes | 3 × 12AX7A; 1 × 12AT7 |
| Rated Power Band | 20Hz to 20kHz |
| Frequency Response | 20Hz to 20kHz: +0/-0.5dB; 10Hz to 70kHz: +0/-3dB |
| Total Harmonic Distortion | 0.3% maximum from 250mW to rated power; less than 0.20% at 1 watt |
| Signal-to-Noise Ratio | 120dB below rated output |
| Dynamic Headroom | 2.4dB |
| Damping Factor | Greater than 25 wideband |
| Inputs and Outputs | Balanced and unbalanced |
| Dimensions | 18 in W × 11-13/16 in H × 21-5/8 in D |
| Weight | 121 lb; 147 lb shipping weight |
Frequently Asked Questions
Is the McIntosh MC3500 Mk II sold as a pair?
No. The MC3500 Mk II is a single-channel monoblock amplifier and is sold individually. Two amplifiers are required for a standard stereo system.
How many vacuum tubes does the MC3500 Mk II use?
Each amplifier uses eight EL509S output tubes, three 12AX7A tubes, and one 12AT7 tube, for a total of twelve vacuum tubes per monoblock.
Can it power 2-ohm speakers?
Yes. The Unity Coupled output transformer provides dedicated connections for 2-, 4-, and 8-ohm loudspeakers, with a rated output of 350 watts at each impedance.
Does the MC3500 Mk II need ventilation?
Yes. This is a high-powered vacuum tube amplifier and should be installed with generous airflow around the chassis and above the protective tube cage.
What warranty is included?
New units purchased through an authorized McIntosh dealer include McIntosh’s 3-year limited warranty, subject to the manufacturer’s current registration and warranty terms.
Authorized McIntosh Dealer Support
Audio Exchange is an authorized McIntosh dealer serving Richmond, Central Virginia, and clients planning reference-level audio systems throughout the region. Our team can help assess loudspeaker compatibility, preamplifier matching, ventilation and support requirements, trade-ins, delivery, and professional installation.
