MCINTOSH MC2300 SOLID STATE AMPLIFIER - RESTORED AND UPGRADED

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General:

This amplifier is so significant that it has its own Wikipedia page:
"The MC-2300 is a solid-state power amplifier which was built by the American high-end audio company McIntosh, and sold between the years 1971 and 1980. It can be utilized either as a 300-watt-per-channel stereo amp, or a 600-watt monoblock, and was rated by its manufacturer as being able to produce this amount of power continuously, with very little (less than 0.25%) distortion. McIntosh's ratings were conservative, however, because like many of their amplifiers, when bench-tested the MC-2300 has frequently been found to produce an even higher level of clean power."

"As such, it was ideal for use in demanding, professional applications. Most famously, the improvisational rock band the Grateful Dead employed 48 McIntosh MC-2300 amps as the main power source for their enormous public-address system, the Wall of Sound. Designed by Owsley "Bear" Stanley and others, this system utilized more than 26,000 watts of continuous power fed into JBL and Electrovoice speakers, and was renowned for its natural, low-distortion stereo sound which carried for 600 feet without significant degradation. The Wall of Sound was only in use from March to October 1974.”

Plus this MC2300 was restored in-house.

This particular piece is in perfect working condition and is in excellent cosmetic condition. It was tested on our test bench to its full rated power and passed with flying colors. All bulbs work, and both meters are responsive. 

The top cover which usually suffers from oxidation is rust free and the stencils are intact. The meters are clean and clear, and the faceplate is also perfect.  I doubt there is another unit out there in this condition and the price we've listed reflects this.  

It's finished in a light champagne color with black paint. Includes a power cord.

Please note this weighs 128 lbs. and will require two people to successfully unbox and set into place.

SkyFi Cosmetic Notes:
This unit arrived to us in rough shape, but we addressed everything that we could. It also features a brand new faceplate and LED lighting. Overall its in more than presentable condition now. 

SkyFi Technical Notes:
This amp is an early 1Y Version. In this version, the fans are always on when the unit is on.

The electronic restoration of this unit included a full reworking of the driver cards, paying special attention to the official McIntosh service bulletin for MC2100/2105/2300. The driver cards received all new electrolytic caps, new matched differential input transistors, new driver transistors and heat sinks, and a full check of all of the remaining resistors and semiconductors.

We also recapped the input and meter boards, replaced a broken 20A mains breaker, installed new gold plated RCA jacks, and replaced the stereo/mono switch. After the electronic restoration was completed, we confirmed that both channels operated simultaneously to rated power and calibrated the meters appropriately.

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:
Speaker terminals and RCA Input Jacks.

General Sound:
Neutral sound with little to no coloration

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.

Included:
Just the unit and power cord.

Packing:
Will be packed using our highly developed in-house process and custom packing materials.Specs:
ELECTRICAL: 300w/ch. (600w mono). Response 20-20kHz (+0 -0.5dB). Distortion 0.25%. Noise and hum -90dB. Output impedance 0.5, 1, 2, 4, 8 and 16 ohms. (0.25, 0.5, 1, 2, 4 and 8 ohms in mono). Damping factor 14 or greater. Input impedance 200k. Input sensitivity 0.5v. Sentry Monitor.

FRONT PANEL: Anodized gold and black panel. Power level (meters read +3 at 300w). Gain controls. Meter range sw: -20, -10, 0, and off. Power sw: on or off. Handles.

BACK PANEL: Output barrier strips. Audio inputs. Mode sw: stereo or mono. Circuit breaker. Dual cooling fans.

Dimensions:
19" rack mounting Width, 10-1/2" Height and 17" Depth.

Weight:
128 lbs.

Link to Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Speaker Cables - Better

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

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.