McIntosh MC275 MK-IV Tube Amplifier, McIntosh "Heart and Soul" Glorious Tube Sound

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Very clean example of the famous McIntosh MC275 design, in its MK IV or MK 4 designation (second next to newest).

The MK IV sounds as good, if not better than the current MK VI, and foregoes what many think to be silly LED lighting on the tubes and the more complicated speaker binding posts.

This example was fully tested in-house and is working tp McIntosh specifications throughout. 

Condition is very good to excellent all around. The tube cage and transformers don't have any of the typical scratches, and the chrome is super clean.

Some of the stenciled writing has come off the stainless steel chassis and there are some light blemishes to the chassis between the tube sockets. Otherwise as clean as you'll find.

(From our technician "This era of MC275 production unfortunately used a silk screening method which resulted in weak lettering".)

Check out this video from our YouTube channel on a past MC275 we offered for sale:

Recommended Cables:

Kimber Kable - RCA Interconnects

Kimber Kable - XLR Interconnects

Kimber Kable - Speaker Cables

Kimber Kable - Bi-Wire Speaker Cables

Kimber Kable - 14AWG (Gauge) Power Cords

Manual:
Click Here

Specifications (from this excellent MC275 generation comparison PDF from The McIntosh Compendium website):

MC275 [MK IV], Sold from March 2004 through December 2006

Specifications:
75W/ch Stereo into 4, 8, or 16 ohms
150W Mono into 2, 4, or 8 ohms

Response:
20-20kHz
(+0 -0.2dB)

Distortion:
0.5%

Noise & Hum:
- 100dB (A weighted)

Output Impedance:
4, 8, 16 ohms
(2, 4, and 8 ohms in mono)
5V line

Damping Factor:
Greater than 14

Input Impedance:
100k unbalanced
180k balanced

Input Sensitivity:
1.2V unbalanced
2.5V balanced
**Unity Coupled

Power Requirements:
120V at 6.3 Amps

Tube Complement:
4 x KT88/6550 output
3 x 12AX7A
4 x 12AT7
Solid state rectifier bridge

The SkyFi Testing Process for Tube Amplifiers:
We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and tubes are inspected for signs of stress overheating or cracking.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If it all looks clean we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier the remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will also be tested.

We also test all tubes for output gain and leakage on our modern and professional calibrated tube tester against the original manufacturers specifications. If needed, the tubes will be replaced from our vast NOS (New Old Stock) vintage or modern inventory.

Final testing involves pushing actual music thorough the amplifier. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage KEF speakers that we're very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice.