mcintosh mc275 power amplifer tube

McIntosh MC275 MK IV Review

McIntosh MC 275 MK VI is a legendary amplifier. Sure most of you will know who McIntosh are and bet some of you will remember the first McIntosh MC 275 that debuted in 1961. Just think about that for a second, this amplifier design has been in production for pretty much 60 years.

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The Brief History of MC275

the McIntosh MC 275 debuted in 1961 and was in production until 1972. McIntosh made and sold thousands of them. The MC 275 was brought back into production in 1994 to commemorate Gordon Gaw, another McIntosh company Legend. It stayed in production since right up until today, and it’s now in its sixth iteration. Though certain parts of being changed and improved and safety measures improved, McIntosh has essentially kept the visual styling very much the same.

First Generation

The first MC275 tube stereo power amplifier was released in the fall of 1961. Since 1961, the smooth, clear and powerful tone of the legendary McIntosh MC275 has always been the quality standard of power amplifiers. In the ten years since the first generation of MC275 was launched, more than 6000 units have been sold. For music lovers who purchased heavy-duty speakers from leading manufacturers in the 1960s, McIntosh MC275 was the first choice in the field of stereo amplifiers.

Second Generation: MC275 Gordon Gow Commemorative Edition, 1993

In response to consumers’ requests, especially from McIntosh’s Japanese distributors, McIntosh decided to release a limited edition of MC275 amplifiers in 1992. These amplifiers have been improved based on the original version, combining the design of the 1990s with the tube structure similar to the original version.

Customers worldwide ordered thousands of MC275s randomly, and McIntosh was shocked by the vast demand for this reprinted amplifier. For the first time, this achievement revealed to the company the huge potential of the modern McIntosh electron tube market.

Third Generation: MC275 non-commemorative edition, 1995-2003

By 1995, the demand for MC275 remained unabated, and people called for re-releases of C22 tube preamplifiers, and the third version of MC275 came into being. The third edition is similar to the Gordon Gow commemorative edition, but without any commemorative nameplate.

Fourth Generation: MC275 stainless steel brand new design, 2004-2007

In 2004, McIntosh’s engineering and technical team thought it was time to redesign the MC275 to use the company’s latest creative capabilities. Although the overall appearance of this generation of MC275 is similar to the previous ones, the most significant feature is the modern structure inside. The integrated and straightforward circuit board eliminates countless plug-in connectors and circuit boards. The new circuit board also designs electronic tube heat dissipation pipes to provide heat dissipation for the output operation of large electronic tubes and the additional external output operation of high voltage.

In terms of appearance design, the base material is improved to corrosion-resistant polished stainless steel. Most importantly, McIntosh has improved the signal-to-noise ratio of the new generation MC275. Compared with other competing similar designs, the final result of all the improvements of the MC275 is a tube amplifier without any audible background noise. MC275 also retains the original classic while making adjustments.

Fifth Generation: MC275 stainless steel brand new design, 5-way speaker terminal, 2007-2011

To facilitate the use of modern Y-shaped plugs and banana plugs, the latest current version of MC275 adds a gold-plated 5-way terminal. The company continues to innovate, and this change also conforms to the needs of consumers. Besides, the fifth generation also eliminates the left and right channel to gain control.

Since the re-launch of MC275 in 1993, the total sales of different versions of MC275 are more than five times the sales of all McIntosh products in the 1960s. Regarding the sales volume of all products in the 1950s, MC275 has always ranked first and lasted for a long time.

Sixth Generation: MC275 50th Anniversary Limited Edition, 2011

Combining brand-new features, a new classic that caters to modern audiophiles’ needs, an amplifier that maintains the quality traditions that has always been carried out has become the most respected amplifier ever.

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The specification of the six-generation has remained pretty much unchanged as well. The MC 275 MK IV is an all-tube stereo 75 watts per channel power amplifier. It’s also a 150 watts per channel monoblock amplifier. Because of McIntosh design and unique technologies, it has the same power output regardless of the output load impedance. So virtually the same power at 8, 4 and 2 ohms. It does that with 0.5% distortion.

One of the included McIntosh technologies is the unity coupled circuit. This patented circuit allows low distortion for flat frequency response and operation of the tubes. This technology again helps the amplifier to have a flat frequency response.

Century monitor tube protection is a circuit that monitors the tubes and ensures a long and healthy life. It is an automatic safety shutdown should there be any problems with the amplifier. The MC 275 is only medium in size, seriously heavy over 30 kilograms, despite having a chassis made from titanium.

The Connections

The speaker binding posts are also a McIntosh patented design. The MC 275 is pretty simple in use. It has single-ended and balanced input connections, on/off the power switch and trigger inputs. It also has an eco on and off switch. If this enabled, the amplifier will automatically go into standby if it doesn’t receive a signal for more than 30 minutes.

mcintosh mc275 power amplifer  connections

The gold-plated speaker connector can be easily connected without loss of power. Both balanced input and unbalanced input interfaces have excellent and reliable quality, further realizing the amplifier’s flexibility.

The Tubes

The primary power tubes are kt88, and there four of them. There are seven smaller tubes, three 12AX7A for input and phase inverter and four 12AT7 for voltage amplifier and driver. These appear to be pretty common tube so it would be great for audiophiles who like to do some tube rolling.

The seven small electron tubes will be heated one by one, and each small electron tube will emit bright amber light one by one until the amplifier reaches a stable operating state, the light of the electron tube will turn green. When all the tubes turn green, the voltage has stabilized, and the amplifier can be used.

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When one of the tubes fails, the high-speed current monitoring protection circuit will intervene and shut down the amplifier before further damage occurs. Intervene and turn off the amplifier before damage to the tube occurs. If the tube flashes red, it means that the tube needs to be replaced, which significantly simplifies the amplifier’s maintenance.

Since the full electronic tube circuit design ensures that the input signal is only amplified by the electronic tube, the speaker will not generate any noise before the amplifier is heated and enters a stable working state.

Sound Performance

What does the MC 275 MK IV sound like? McIntosh themselves say the MC 275 doesn’t have a sound signature. They say it has the sound signature of the music. It’s hard to describe in words what’s something that sounds musical might mean. When you listen to the McIntosh MC 275, you can see why it’s been in production and still selling for all these years. It’s a great sounding amplifier. Music sounds smooth and euphoric, and it’s a real pleasure to listen to. But it’s still plenty of drive masses of control, fantastic bass extension and again bass control.

I expected some apparent negatives to sound performance because the McIntosh 275 isn’t an all-valve amplifier and only 75 watts. But I’m happy to report there just wasn’t any. I would say the McIntosh engineers are not working the tubes in this product overly hard. Coupled with the innovative McIntosh design and technologies, it creates an amplifier with an effortless presentation of even loud volumes. It does have a maximum volume point where the sound quality seems to degrade if you go over. But that’s a very loud volume level more than loud enough for the majority of audiophiles.

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The MC 275 is also very transparent to the source. It doesn’t always sound smooth and doesn’t sound smooth if you don’t want it to. A real surprise to me was the heat that the amplifier doesn’t generate. I was expecting it to be like having a little oven in the listening room. It just doesn’t seem to generate any more heat than some of our transistor plus a/b designs. However, I would still give the McIntosh 275 plenty of ventilation.


This is not a cheap amplifier with a retail price of over 7,000 pounds. However, the visual styling and the sound quality more than justify that price tag. You also get the legendary McIntosh to build quality with most parts and assembly is done in-house.

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I’m thrilled with the build quality of the MC 275. I do have a couple of niggles, but they are not ones that would put me off buying. My final thoughts I know valve amplifiers can be very precious to certain audiophiles. The McIntosh MC275 was designed back in 1961 with some extreme foresight. Current modifications have kept it very much up to date. Instead, I think MC 275 is a valve amplifier for nearly every audiophile. It’s very, very, very easy to live with and even more comfortable to love. It won me over instantly. It’s a charming and simply wonderful Hi-Fi component to listen to.

McIntosh MC275 MK IV Specs

  • Power Output per Channel: 75W @ 4, 8 or 16 Ohms
  • Number of Channels: 2
  • Total Harmonic Distortion: 0.5% maximum harmonic distortion at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz (≤ 0.25% harmonic distortion at 1kHz)
  • S/N below rated output: 105dB
  • Dynamic Headroom: 1.2dB
  • Damping Factor: >22
  • Rated Power Band: 20Hz to 20kHz
  • Frequency Response : +0, -0.5dB from 20Hz to 20,000Hz / +0, -3.0dB from 10Hz to 100,000Hz
  • Remote Power Control: Yes, input and output
  • Circuit Configuration: Unity Coupled
  • Circuit Design: Vacuum Tube
  • Mono Bridge: Yes
  • Mono Parallel: Yes, 150W @ 2, 4 or 8 Ohms
  • Output Type: Unity Coupled Output Transformer
  • Meter Light Switch: Small signal tubes LEDs controlled by McIntosh preamp
  • Balanced Input: Yes
  • Illumination: Small Signal Tubes, LED
  • Chassis Style: Polished Stainless Steel
  • Speaker Binding Post Type: Patented Solid Cinch™ Speaker Binding Posts
  • WEIGHTS & DIMENSIONS Dimensions (W x H x D): 21-1/2″ (54.6cm) (including cables) x 8-1/2″ (21.6cm) (including feet) x 12″ (30.5cm)
  • Weight: 67 lbs (30.5 kg)
  • Shipping Weight: 75 lbs (34.1 kg)