McIntosh MC7270 "Blue Monster" Amplifier, Electronically Restored, 270W x 2

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This is my personal MC7270 that I bought to match my C36 & MR500 from the same 1980's era of McIntosh.

This was the system I listened to hour after hour, days on end during work in my smaller office from the start of COVID through most of the pandemic.

(C36 & MR500 both sold out within days after listing).

Dynamic music from the 1970's and 1980's sounds like nothing else on this high-powered amplifier. Even with smaller speakers.

I loved the massive up-front big blue VU power meters from the start and is the main reason I bought it. Then with the C36 & MR500 it matched the rest of my system and looked stunning even when powered off.

It's been sitting with little use for over a year now from the amount of short and long term gear we test at the shop.

After a lot of thought I've decided to list this for sale to find a happy new home.

This MC7270 received a fresh front glass faceplate from the McIntosh along with fresh bulbs, but I decided to otherwise leave it "vintage".

You see I rescued this MC7270 - it wasn't working at all when I came across it several years ago and it was about to be sold for parts or maybe trashed.

It had moved a lot with the original owner and therefore endured many "love taps" from being moved around since it weighs over 80 lbs! We find this a lot with big heavy amplifiers from this era and older.

The seller wasn't sure what was wrong with it, it had been sitting for many years, and was told by a technician friend that some "minor repairs" were all that were needed by someone more familiar with McIntosh.

Well that repair estimate was... off.

To begin with someone had actually clipped off the leads of several transistors after removing them, reinstalling them broken to try and pull one over on the next buyer!

That was just the start of what we found wrong unfortunately. 

Next our in-house technician and McIntosh repair guru pulled this apart and made short work of diagnosing the many issues to determine next steps.

After putting together a lengthy list of parts, I made the call to restore this vintage monster vs parting it out. Just didn't seem right.

This MC7270 is now working perfectly with no issues.

Physical condition of the front faceplate is like new, however the rest of this amplifier is basically a 6 and maybe a 7 in some areas due to scratches, scuffs, indentations, small dents, etc. as shown in our photos.

Since you're stating at this beauty head-on or at a front angle95% of the time I don't think it will bother most people. Never bothered me and I liked the "patina" of the originality. 

I also decided to keep the original incandescent lighting which matched better with the rest of this McIntosh 1980's system. Only physical change was the original big gray caps replaced to cool-blue modern replacements to match the front meters.

We have an official replacement MC7270 box on order from the factory that we should receive soon to ensure safe travels to your home. It's the only way to ship something this delicate and heavy to ensure it arrives as it left. Local pickup is also welcome!

SkyFi Electronic Restoration Notes:
• Repaired damaged input RCA jacks.
• Full electrolytic recap.
• All output transistors replaced.
• Front faceplate glass replaced.
• All incandescent bulbs changed.
• Main filter capacitors changed.
• Meter calibration.
• Bias and DC Offset set to Service Manual spec.

McIntosh MC7270 Owner's Manual

Stereophile MC7270 Review from 1987

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 - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Speaker Cables - Better

Summit Series Monocle XL Speaker Cables (PAIR) - Best

Summit Series BiFocal XL Bi-Wire Speaker Cables (PAIR) - Best 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.