McIntosh C28 Vintage Solid State Preamplifier - Survivor

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General:
The C28 solid state preamplifier is a true McIntosh classic. It features the McIntosh vintage look and feel including a backlit glass faceplate, large polished control knobs, and satisfying push-buttons with LED's.

Controls are just what you need - an input selector, volume, balance, plus tone controls. The individual left and right channel tone controls are a nice plus.  

Cosmetically it presents very nicely. The glass faceplate is clean and the chassis is free of rust or any significant wear.

The C28 is a crowd favorite from this era. It has great vintage looks, a low noise floor, and every feature we would want.

This particular C28 looks to be a survivor with all its original parts intact. The buttons and knobs feel super nice without any scratchiness. It sounded great in testing and at our bench. 

We ordered a fresh C28 double-shipping carton from McIntosh to ensure safe travels to its new home.

SkyFi Cosmetic Notes:
Light wear is present on all surfaces. There are some scratches on the top of the faceplate bezel, and the panloc text is a bit faded.

SkyFi Technical Notes:
This C28 arrived to us in "working" condition. All functions were tested and fundamentally work. As far as we can tell this unit is all original besides the four panel lamps for illuminating the glass. We have fitted a fresh set of period correct 1866 incandescent lamps in these positions. Survivor.

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, Power Outlets, Captive Power cord

General Sound:
Smooth, uncolored, undistorted natural and clean

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:
Frequency response: 20 Hz to 20 kHz
Total harmonic distortion: 0.1%
Gain: 62 dB (MM), 20 dB (line)
Input sensitivity: 2.5mV (mic), 2mV (MM), 250mV (line)
Signal to noise ratio: 78 dB (MM), 90 dB (line)
Output: 250mV (line), 2.5V (Pre out)

Dimensions:
16" x 5.4" x 15"

Weight:
25 lbs.

Approximate Age:
1970

Link to Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects

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.

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 1 KHz 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 1 KHz 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.