McIntosh MC7100 Version II Compact Amplifier w/Balanced XLR

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General:
Built to the same standards and component quality as all other McIntosh amps from this era, but in a compact chassis.  

We love the high quality and super capable speaker connectors on the back, which makes us wish they still made them like this. 

Includes single ended AND balanced XLR inputs. Built like a tank and fully tested.

This particular example was serviced before at a McIntosh Clinic and will come with its vintage clinic test paperwork as proof. It also comes with its original owners manual and box. 

Performance Features Include:
SENTRY MONITOR CIRCUIT
• All power transistors have limits for the maximum amount of power they can handle. The MC7100 output transistors and power supply have been designed to allow very high current flow into properly matched load impedances. However, if a short circuit or very low load impedance is connected to the MC7100 outputs, destructive current levels could be reached if it was not controlled by the SENTRY MONITOR circuit.

THERMAL CONTROL
• All power transistors have limits to the maximum amount of heat they can safely tolerate. The MC7100 uses a highly efficient amplifying circuit which produces relatively little heat for the output power produced. The amplifier uses large area heat sinks to efficiently dissipate what heat it does generate. Natural convection air flow is sufficient for safe cool operation.

POWER GUARD
• A unique and patented feature of Mclntosh power amplifiers insures that each channel of the MC7100 will deliver full power, free of clipping distortion. A Mclntosh power amplifier with POWER GUARD will always deliver its maximum distortion free output. This power is always well above the rated power due to the Mclntosh philosophy of conservative design.

SkyFi Cosmetic Notes:
This amplifier has light cosmetic blemishes along the edge of the faceplate. The other metal surfaces also show some wear. This amp has two official McIntosh Clinic stickers from the 1990's.

SkyFi Technical Notes:
This version of the MC7100 has a wide chassis and is fitted with an input board that allows both single ended (RCA) and balanced (XLR) connections. 

This unit also recently received a new set of main filter capacitors sourced directly from the McIntosh factory, along with fresh incandescent lamps.

Brand Background:
McIntosh Laboratory is an American manufacturer of handcrafted high-end audio equipment based in Binghamton, New York. The company was founded in 1949 by Frank McIntosh. The company designs and produces audio amplifiers, stereo tuners and other consumer electronics products.

Ownership:
Single Owner

Connections:
RCA, XLR, Speaker Binding Posts, Power Outlet, Power Control in/out

General Sound:
Smooth, uncolored, undistorted natural and clean

Cosmetic Condition:
8/10 = Very Good. Excellent front faceplate, one minor flaw on chassis side or top. See our detailed rating description here.

Working Condition:
Working perfectly and tested in our lab and listening room.

Packing:
Original Manufacturers Packing

Specs:
STEREO POWER OUTPUT
150 watts into 4 ohm loads or 100 watts into 8 ohm loads minimum sine wave continuous average power output per channel, both channels operating.
The output RMS voltage is:
28.3V across 8 ohms
24.5V across 4 ohms

MONOPHONIC (BRIDGED)
300 watts into an 8 ohm load minimum sine wave continuous average power output. The output RMS voltage is: 49 volts across 8 ohms.

OUTPUT LOAD IMPEDANCE
STEREO
8 or 4 ohms
MONOPHONIC
8 ohms

RATED POWER BAND
20Hz to 20,000Hz

TOTAL HARMONIC DISTORTION
0.005% maximum harmonic distortion at any power level from 250 milliwatts to rated power output.

IHF DYNAMIC HEADROOM
8 ohms, 1.7dB
4 ohms, 2.1dB

FREQUENCY RESPONSE
+ 0, -0.25dB from 20Hz to 20.000Hz
+ 0, -3.0dB from 10Hz to 100,000Hz

INPUT SENSITIVITY
1.4 volts (2.5 volts at gain control center detent)

A-WEIGHTED SIGNAL-TO-NOISE RATIO
95dB (115dB below rated output)

INTERMODULATION DISTORTION. SMPTE
0.005% maximum if instantaneous peak power output does not exceed twice the output power rating.

RATINGS
WIDE BAND DAMPING FACTOR
8 ohms, 200
4 ohms, 100

INPUT IMPEDANCE
20,000 ohms

POWER GUARD
Clipping is prevented and THD does not exceed 2% with up to 14dB overdrive at 1000Hz.

POWER REQUIREMENTS
120 volts, 50/60HZ, 3.0 amps UL/CSA

Dimensions:
Front panel: 17 1/2 inches (44.5cm) wide, by 3 5/8 inches (9.2cm) high.

Chassis: 14 3/4 inches (37.5cm) wide, by 2 3/8 inches (6cm) high, by 14 1/2 inches (36.9cm) deep, (from back of front panel), in- cluding connectors. Panel clearance required in front of the mounting surface is 1 inch (2.54cm).

Weight:
25 lbs.

Link to Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - BALANCED XLR Connectors - Better

Kimber Kable - BALANCED XLR Connectors - Best

Kimber Kable - Speaker Cables - Better

Kimber Summit Series Monocle XL Speaker Cables (PAIR) - Best

Kimber Summit Series BiFocal XL Bi-Wire Speaker Cables (PAIR) - Best If Applicable

Kimber Kable - Power Cords - Better

Kimber Kable - Power Cords - Best

Testing Process:
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 1 KHz 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 1 KHz square wave check and a 20 Hz to 20 KHz 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 minimum. 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.