McIntosh MC2300 Solid State Amplifier - Serviced - "Grateful Dead Wall of Sound"

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General:
The McIntosh MC-2300 is one of the most iconic amplifiers of all time. This was the very model that powered the Grateful Dead's famous wall of sound in 1974.

Rated at 300 Watts into 8ohm stereo it can power even some of the most demanding speakers with ease. If you are lucky enough to have two of these amplifiers you can run it in mono mode for whopping 600 Watts!

This particular MC2300 was serviced in-house. making it particularly desirable. It tested on our test bench to its full rated power and passed with flying colors. All bulbs work, and both VU meters are responsive. 

Included with the Amplifier will be its original manual.

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.”

SkyFi Cosmetic Notes:
Cosmetic blemishes include light scuffs and marks on surfaces. The faceplate has some light scratching and blotchiness that can be noticed in direct light. The meter illumination has been converted to cool white LED which more closely matches the cyan color of current McIntosh meters. Due to aging of the plastic parts one meter is slightly differently colored than the other. We are including the original incandescent lamps if you would like to revert to stock illumination. Overall the condition is very good.

SkyFi Technical Notes:
This unit was serviced here at SkyFi Audio. We rebuilt the driver cards, applying the necessary service bulletin updates, recapped the input and meter boards, and replaced the output barrier strips and RCA jacks. The meters were also calibrated and controls cleaned. This unit bench tested to over 300W per channel into 8 ohms, both channels driven.

NOTE: This is a relatively early unit and has no temperature sensing for the fans. The fans run whenever the unit is turned on. The fans may be audible depending on your listening position.

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:
RCA, AC Power Input, Binding Posts.

General Sound:
Big beautiful musical sound with little fatigue.

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:
Unit and Manual

Packing:
Will be packed using our highly developed in-house process and custom packing materials.Original MSRP:
$1,799.00

Specs:
Power output: 300 watts per channel into 8Ω (stereo), 600 watts into 8Ω (mono)
Frequency response: 20Hz to 20kHz
Total harmonic distortion: 0.25%
Damping factor: 14
Input sensitivity: 0.5V
Signal to noise ratio: 90dB
Speaker load impedance: 0.5Ω to 16Ω
Semiconductors: 46 x transistors, 22 x diodes

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

Weight:
175 lbs.

Approximate Age:
1974

Link to Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - 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.