McIntosh Vintage Solid State Amplifier MC2125

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One of our favorite amplifiers from this period, rated at 125W x 2 channels.

It's not as big and heavy as some of its older brothers, but it's right at a sweet spot for powering most vintage speakers from this era.

Typical Mcintosh features such as a glass faceplate that essentially guarantees things will not age over time.  Most amplifiers made with metal faceplates tend to either get scratched up or the writing rubs off over time.  But due to the glass, McIntosh amplifiers and preamps still look amazing even after 30-40 years of use.

(The glass is so shiny that it reflected what looks like a glass imperfection in the first several photos - this is ONLY in the photos)

Here's a full SkyFi video review:

This particular piece is a great example, as you can see the glass is pretty much intact and looks like the day it left the factory even through its had some use. Features the beautiful glowing blue meters you've come to expect and love in McIntosh amplifiers.

And one of the nice features about vintage McIntosh is that it looks great even when matched or mixed with current McIntosh.  They kept the same design language so you can mix a modern C48 preamp with this MC2125 vintage amplifier and have it all kind of look cohesive and work well together.  

Simple overall operation, yet you'll find more controls than you would on a normal modern amplifier.  You have individual left and right channel gain controls allowing you to just dial in the amount of gain for each channel. A control for the meters range which lets you pick between -20dB, -10dB, 0 dB, MEASURE, or HOLD a maximum setting.  Corresponding to this control you will see 3 indicators for "WATTS", "HOLD", and "DECIBELS" change on the front between the meters.

There's a speaker output on/off control knob in case you're making adjustments and want to eliminate the connection to the speakers.  A power knob (of course).  And over on the right you'll see the soft clipping features known from McIntosh as their POWER GUARD technology.  Under normal operation this will stay green, then when you've reached the 125W potential maximum output these lights will start to flicker orange letting you know that yo've reached the maximum power output. Yet it will do it conservatively to make sure the amp stays protected.  

On the back you'll see 2/4/8/16 Ohm taps with is also very unique to McIntosh.  They use autoformers on the output stages which allows you to have direct taps to allow the most efficient connection depending on the impedance of your speakers.

On the back there's a convenience outlet to power something from this amp, a switch that allows you to enable/disable POWER GUARD, a stereo/mono mode switch that allows you to switch/bridge into mono around 250-300W for a single channel, and input sensitivity in case you've got a preamp that's a little high or low in this setting.  You can get the most from the potentiometer on your preamp by adjusting this between 2.5 ~ 0.75 volts.

This amplifier can be placed into a McIntosh case.  You'll see the sliding rails on the side with the Panlocs that let you attach this amplifier to the case.  A very cool feature.

This particular sample is in really nice condition.  The faceplate does not exhibit bubbling of any sort, the top cover work is super clean, there's no rust or scratches or anything of the sort, and more importantly (the achilles heel of these amplifiers) is the chrome-work.  If stored in any damp environment over time (someone's basement or attic), they tend to rust and the chrome starts to pit.  But this example apparently had a very nice life as there's no pitting whatsoever on the chrome.  It's super bright and shiny and in beautiful condition.

Our technicians tested this amplifier in our lab and ran it to its full rated power and watched POWER GUARD function correctly at the full rated output.  And we did a full inspection to make sure there were no capacitors or components that needed replacing.  

This listing includes just the amplifier.

Click here for a PDF copy of the MC2125 Owner's Manual

Our Testing Process for Amplifiers (Solid State) at SkyFi:

(Along with this video showing an example with a similar piece from McIntosh):

We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and transistors are checked for signs of stress or damage.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally, we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If everything reads clean, we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier then remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will be also be tested.

Final testing involves pushing actual music thorough the amplifier. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage Kef speakers that we're very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice.

Technical Specifications:

POWER OUTPUT
STEREO
120 watts minimum sine wave continuous average power output, per channel, both channels operating into 2 ohms, 4 ohms, 8 ohms, or 16 ohms load impedance, which is;
15.5 volts RMS across 2 ohms
21.9 volts RMS across 4 ohms
31.0 volts RMS across 8 ohms
43.8 volts RMS across 16 ohms

MONO
240 watts minimum sine wave continuous average power output into 1 ohm, 2 ohms, 4 ohms, or 8 ohms load impedance, which is:
15.5 volts RMS across 1 ohm
21.9 volts RMS across 2 ohms
31.0 volts RMS across 4 ohms
43.8 volts RMS across 8 ohms

OUTPUT LOAD IMPEDANCE
STEREO
2 ohms, 4 ohms, 8 ohms, and 16 ohms;
separate terminals are provided for each output

MONO
1 ohm, 2 ohms, 4 ohms, and 8 ohms; obtained by connecting together the appropriate terminals of both channels

RATED POWER BAND
20 Hz to 20,000 Hz

TOTAL HARMONIC DISTORTION
STEREO
0.1% maximum harmonic distortion at any power level from 250 milliwatts to 120 watts per channel from 20 Hz to 20,000Hz, both channel operating

MONO
0.1% maximum harmonic distortion at any power level from 250 milliwatts to 240 watts from 20 Hz to 20,000 Hz

INTERMODULATION DISTORTION
STEREO
0.1% maximum if instantaneous peak power output is 240 watts or less per channel with both channels operating for any combination of frequencies, 20 Hz to 20,000 Hz

MONO
0.1% maximum if instantaneous peak power output is 480 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 100,000 Hz +0 -3.0 dB

NOISE AND HUM
95 dB below rated output

SEMICONDUCTOR COMPLEMENT
45 silicon transistors
45 silicon rectifiers and diodes
8 integrated circuits

MECHANICAL INFORMATION
SIZE
Front panel measures 16 inches wide (40.64 cm) by 5-7/16 inches high (13.81 cm).
Chassis measures 15 inches wide (38.1 cm) by 5 inches high (12.7 cm) by 13 inches deep (33.02 cm), including connectors.
Knob clearance required is 11½ inches (3.81 cm) in front of mounting panel

FINISH
Front panel is anodized gold and black with special gold/teal nomenclature illumination. Chassis is chrome and black

WEIGHT
65 pounds (29.5 kg) net, 77 pounds (35 kg) in shipping carton

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.