McIntosh MX112 Vintage Tuner/Preamp with Phono - Serviced

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First MX112 to come through the shop!

Seems to be as capable and feature rich as the venerable MX110, but with solid state rather than tubes, and with the addition of the AM band.

It's also much less complicated in design and execution.

Cosmetically it fits the bill: large backlit tuning meter, glass front faceplate, and easy to use buttons and knobs.

Controls are just what you need, input selector, volume, balance, and tone controls.

This example is in nice condition and has been serviced in our shop for trouble-free operation. The paintwork is super clean and the chome presents nicely.

A matching and well fitting wood cabinet is available for thisMX110, just drop us a note if interested.

An owner's manual is included but it is a copy and not an original.

SkyFi Cosmetic Notes:

• Serial number and the letters "RDC" lightly etched into the right end-cap.
• Internal glass dial lettering starting to fail on certain numbers (see photos).
• Light glass blemishes.

SkyFi Service Notes:

• This unit received a routine servicing which included cleaning all of the controls, checking all lamps, and performing a tuner alignment touch up.
• The original volume control had very bad channel balance and has been replaced with the recommended part from the McIntosh parts department. The new control works well but appears to be linear taper meaning that it goes up in volume very quickly during its rotation, we therefore recommend running this device with a power amplifier with input attenuators. Most vintage solid state and tube amplifiers from McIntosh have this feature.

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects - Better

Kimber Kable - Flagship Phono Interconnects - Best

Link to Manual:

Click Here

Specifications:

Please see above manual.

The SkyFi Testing Process for Preamplifiers:

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 PCB’s 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.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope. We then switch to a 1KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment. Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected. If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.