McIntosh MC2505 Vintage Solid State Amplifier - Serviced Late Serial

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General:
The McIntosh MC2505 delivers a clean 50 watts per channel, making it an excellent pairing for most medium- to high-efficiency speakers and a fantastic way to experience classic McIntosh performance.

Common for MC2505's we have had at SkyFi, it captures the warm, smooth, and musical character that has made vintage McIntosh gear so popular. During testing, we especially enjoyed the way vocals were reproduced; natural, intimate, and wonderfully lifelike.

The MC2505 also features timeless McIntosh styling, with blue illuminated meters, silver knobs, and the iconic glass faceplate that instantly identifies it. An added benefit of this model is that it offers all of these features in a relatively manageable size that is much easier to move compared to many larger vintage amplifiers.

This particular MC2505 has been serviced in house at SkyFi. As a bonus it has its original glass and stock incandescent illumination which looks particularly nice.

As always, this amplifier will be carefully packed with great attention to detail so it arrives safely at its new home.

SkyFi Cosmetic Notes:
The glass on this MC2505 shows blemishes including bubbles on the bottom edge and some paint lifting around the headphone jack, panlocs, and left meter. We opted to leave the original glass in place because the lettering looks really nice with stock incandescent illumination. The chassis has light wear on all surfaces. Light chrome wear. One output barrier strip was replaced due to damage. Overall given its age it presents very well.

SkyFi Technical Notes:
This unit was fully serviced in house here at SkyFi. We rebuild the speaker on/off switch which had become intermittent, replaced a damaged output barrier strip, cleaned the controls, and performed preventative maintenance. The input and driver boards were reworked with new electrolytic capacitors and select transistors as needed. The meters have been calibrated and the unit was tested for proper output power - clipping at around 60WPC.

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, Speaker Binding Posts, Captive Power cord

General Sound:
Smooth, uncolored, undistorted natural and clean

Cosmetic Condition:
7/10 = Good. One or two minor scratches. Well Maintained. 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:
Original Manufacturers Packing

Specs:
Power output: 50 watts per channel into 8Ω (stereo)
Frequency response: 20 Hz to 20 kHz
Total harmonic distortion: 0.25%
Damping factor: 10
Input sensitivity: 0.5V
Signal to noise ratio: 90 dB
Speaker load impedance: 4Ω to 16Ω

Dimensions:
Size: 5-7/16"H, 16"W and 13"D

Weight:
38 lbs.

Approximate Age:
1967

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.