McIntosh MC7270 - Super Clean - 270Wx2 - Best Mc Amp from this Era

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The 7270 is by FAR one of our favorite vintage amps from McIntosh.

Aesthetically it meets all the requirements - large chassis, big blue meters, glass & metal faceplate, and BIG power.

Cosmetically it would be hard to find a cleaner unit.

This particular sample is in great shape and passed all of our internal tests with ease.

From our lab:

• Replaced front faceplate glass with new glass sourced directly from McIntosh.
• Installed replacement front panel meter switch.
• Rechecked meter calibration - PASS.
• Both channels test above 270W, and clip evenly.
• Tested power guard works on both channels.
• Long term testing - PASS.

This amplifier will ship to you with an official McIntosh Shipping Carton (double-ply and double-boxed).

Review:

Stereophile MC7270 Review from 1987

Manual:

McIntosh MC7270 Owner's Manual

Click below to add our recommended matching cables from Kimber Kable, all brand new as SkyFi is an official Kimber dealer.

Kimber Kable - RCA Interconnects

Kimber Kable - Speaker Cables - Good

Kimber Kable - Speaker Cables - Better

Kimber Kable - Bi-Wire Speaker Cables - Better (If Applicable)

Specifications from McIntosh:
PERFORMANCE GUARANTEE
Performance Limits are the maximum deviation from perfection permitted for a Mclntosh instrument. We promise you that when you purchase a new MC 7270 from a Mclntosh franchised dealer, it will be capable of or can be made capable of performance at or exceeding these limits or you can return the unit and get your money back. Mclntosh is the only manufacturer that makes this statement.

PERFORMANCE
Mclntosh audio power ratings are in accordance with the Federal Trade Commission Regulation of November 4, 1974 concerning power output claims for amplifiers used in home entertainment products.

POWER OUTPUT
STEREO
270 watts minimum sine wave continuous average power output, per channel, both channels operating into 1 ohm, 2 ohms, 4 ohms, or 8 ohms load impedance, which is:
16.4 volts RMS across 1 ohm
23.2 volts RMS across 2 ohms
32.9 volts RMS across 4 ohms
46.5 volts RMS across 8 ohms

MONO-BRIDGE
540 watts minimum sine wave continuous average
power output into 2 ohms, 4 ohms, 8 ohms, or 16 ohms load impedance, which is:
32.9 volts RMS across 2 ohms
46.5 volts RMS across 4 ohms
65.7 volts RMS across 8 ohms
93.0 volts RMS across 16 ohms

OUTPUT LOAD IMPEDANCE
STEREO
1 ohm, 2 ohms, 4 ohms, and 8 ohms; separate terminals
are provided for each output.

MONO-BRIDGED
2 ohms, 4 ohms, 8 ohms, or 16 ohms, balanced to ground.

RATED POWER BAND
20 Hz to 20,000 Hz

TOTAL HARMONIC DISTORTION
STEREO
0.02% maximum harmonic distortion at any power level from 250 milliwatts to 270 watts per channel from 20 Hz to 20,000 Hz, both channels operating.

MONO
0.02% maximum harmonic distortion at any power level from 250 milliwatts to 540 watts from 20 Hz to 20,000 Hz.

INTERMODULATION DISTORTION
STEREO
0.02% maximum if instantaneous peak power output is 540 watts or less per channel with both channels operating for any combination of frequencies, 20 Hz to 20,000 Hz,

MONO
0.02% maximum if instantaneous peak power output is 1080 watts or less for any combination of frequencies, 20 Hz to 20,000 Hz.

FREQUENCY RESPONSE (AT ONE WATT OUTPUT)
20 Hz to 20,000 Hz +0 -0.25 dB.
10 Hz to 100,00 Hz +0 - 2 dB.

NOISE AND HUM
100 dB below rated output.

RATINGS
DAMPING FACTOR
Greater than 30

INPUT IMPEDANCE
20,000 ohms.

INPUT SENSITIVITY
Switchable: 0.75 volt or 2.5 volts-level control provided for higher input voltages.

POWER GUARD
Clipping is prevented and THD does not exceed 2% with up to 20 dB overdrive a 1 kHz.

GENERAL INFORMATION
POWER REQUIREMENTS
120 volts 50/60 Hz; 13 amps.

SEMICONDUCTOR COMPLEMENT
79 silicon transistors
31 silicon rectifiers and diodes
7 integrated circuits

MECHANICAL INFORMATION
SIZE
16 3/16 inches wide (41.1 cm) by 7 1/8 inches high (18.1 cm) by 14 1/2 inches deep (36.8 cm), including connectors. Knob clearance required is 1 1/4 inches (3.2 cm) in front of mounting panel.

FINISH
The front panel is a combination of glass and black anodized aluminum. The chassis is black.

WEIGHT
82 pounds (37.2 kg) net, 96 pounds (43.5 kg) in shipping carton.

The SkyFi Testing Process for Solid State Amplifiers:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

If the amplifier passes visual inspection, we move on to a controlled power on sequence using a Sencore safety analyzer to monitor current draw in real time. Once the amplifier is determined to be safe to operate, we connect it to full AC mains for function and power testing. We connect the speaker outputs of the amplifier to a Sencore PA81 Power Analyzer which acts as a dummy load, DC offset monitor, and oscilloscope interface. We start with a low level 1KHz test signal at the amplifier’s input and slowly increase its amplitude while monitoring the output on an oscilloscope for signs of noise, clipping, distortion, or improper channel balance.

We continue increasing the signal level until the amplifier reaches clipping. At this point we take an output power measurement and compare it to the spec sheet of the amplifier to verify proper performance. If the device under test has both balanced and single ended inputs they are both tested at this time. We finish off the bench evaluation with a 1KHz square wave check and a 20Hz to 20KHz sine sweep to assess the amplifier’s frequency response characteristics. This battery of tests will usually reveal if the amplifier has any issues that need further attention.

Before the device leaves the bench, we perform a listening test with actual music using a variety of preferred test tracks. Our benches are outfitted with familiar monitor speakers which help us identify inconsistencies that will not always show up on our test gear. The main things that we are listening for are hum or noise with no signal present, proper center image, clicks, pops, or any other obvious undesirable audio characteristics.

If the unit passes all of these tests it is moved to our long term testing rig where we simulate real word operating conditions for 6-8 hours. This allows us to monitor the unit for signs of thermal runaway or intermittent issues that only crop up when the unit has fully come up to temperature.