McIntosh MC501 Monoblock Amplifier Pair - Consecutive Serials, Fiber Optic

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General:
The MC501s from McIntosh are notable for their mega powerful 500W output and their form factor, which is much more shallow and manageable than the current version. Unlike many amps this powerful, the MC501 can fit in most cabinets and racks.

A standout design feature is the signature McIntosh 3D faceplate which in our opinion was the best looking of all the series. Thick tempered glass ensures it will not crack in shipping, plus the aluminum trim work looks amazing along with the fiber optic lighting. I suspect this construction type became too expensive for McIntosh to produce so they went back to standard flat face plates on the next version.  

MC501's are perfect for someone who is looking to power their low sensitivity speakers with absolute ease. They also feature XLR inputs for balanced connections. This particular pair sounded amazing in testing.

The current version (MC601s) will set you back $19,000, quite a premium for extra 100w.  

Included will be their original manual, box and plastic rear protecting terminal covers.

Price includes freight shipping to the lower 48 states.  

SkyFi Cosmetic Notes:
Both amplifiers have some silk screen wear and slightly cloudy back panels. We opted to leave them as is to prevent any more silk screen (lettering) loss. Overall the condition is excellent.

From McIntosh: 
Some Performance Features:
• Full Balanced Quad-Differential Circuitry
The MC501 is fully balanced from inputs to outputs. It
consists of two matched power amplifiers operating in push-pull with their outputs combined in a McIntosh Autoformer. The double balanced configuration cancels virtually all distortion.
• Patented Autoformers

The McIntosh designed and manufactured Output
Autoformer provides an ideal match between the amplifier output stage and speaker loads of 2, 4 and 8 ohms. The Autoformer also provides perfect DC protection for your valuable Loudspeaker.

• Patented Power Guard
The patented McIntosh Power Guard Circuit prevents the amplifier from being over driven into clipping, with its harsh distorted sound that can also damage your valuable Loudspeaker.

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:
Second Owner

Connections:
XLR,RCA, Power control, IEC Power

General Sound:
Smooth, uncolored, undistorted natural and clean

Cosmetic Condition:
7/10 = Good. One or two minor scratches. Well Maintained. See our detailed rating description here.

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

Included:
Unit, manual, and power cord.

Packing:
Original Manufacturers Packing

Original MSRP:
$11,000.00

Specs:
Key Technical Specifications:
- Power Output: 500W RMS minimum into 2, 4, or 8 Ohms
- Total Harmonic Distortion (THD): 0.005% maximum at any level from 250mW to rated power
- Frequency Response: +0, -0.25dB from 20Hz to 20kHz; +0, -3dB from 10Hz to 100kHz
- Signal-to-Noise Ratio (A-Weighted): 97dB (124dB below rated output)
- Input Impedance: 10,000 Ohms (unbalanced), 20,000 Ohms (balanced)
- Input Sensitivity: 2.1V Unbalanced, 4.2V Balanced
- Damping Factor: >100 @ 8-Ohms
- Weight: 91.5 lbs (41.6 kg) net McIntosh
-  +3
Features:
- Output Autoformer: Ensures full 500W power delivery regardless of speaker impedance.
- Power Guard: Prevents clipping to protect loudspeakers.
- Design: Black glass front panel, blue wattmeter, and stainless steel chassis.
- Connectivity: Balanced (XLR) and unbalanced (RCA) inputs, with dedicated speaker terminals for 2, 4, and 8-ohm loads.

Dimensions:
(H x W x D): 9.44” (22.86cm) x 17.5” (44.45cm) x 14.81” (37.62cm)

Weight:
91.5 lbs.

Approximate Age:
2003

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.