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Up For Sale is my Conrad Johnson MF 2500 A Solid State Amplifier
Low Use The Only Marks is shown I beveled Ac Inlet To adapt for Audioquest Power cord Included
Power Output: MF2500A – 250 watts per channel. All deliver their power from 20Hz to 20KHz at no more than 1% THD and IM, both channels driven into 8 ohms.
Distortion: less than .1% THD or IMD
Frequency Response: 20Hz to more than 20kHz , +0, -.5dB
Hum & Noise: 100 dB below full power output
Input impedence: 100K ohms
Mechanical: MF2500A 19" X 6 ¾" X 16"
Serial Number: 7821446
Original retail: $3,700.
Michael Wright in 2004 wrote a short review of the Conrad-Johnson MF2500a power amplifier for Stereotimes: http://www.stereotimes.com/amp020804.shtml.
Here is a link to an earlier more extensive review of the Conrad-Johnson MF2500 power amplifier by Marin Colloms in Stereophile: https://www.stereophile.com/solidpoweramps/1299cj/index.html.
For sale is the upgraded MF2500A version which provides more power and better sound. Therefore, the review is not the same model but it is appropriate to include.
Like many Conrad-Johnson designs, the MF2500's higher performance goals have been attained through experience and the refinement of established circuits, not by some magic new topology that's claimed to solve all previously known audio-fidelity problems. Thus the input stage is a standard differential circuit executed with FETs. The second stage comprises a buffered voltage-gain amplifier, and uses bipolar transistors. It drives a regular class-A/B push-pull bipolar output stage, which is direct-coupled to the speaker...
The MF2500's regulation topology is of Premier quality. For example, the input stage has its own transformer tap stabilized at a voltage higher than the output stage requirement. Discrete open-loop regulators have audiophile-grade polystyrene and polypropylene capacitors. Only the main current reservoirs are electrolytic, but here there is no choice. Voltage-reference and feedback-control resistors are costly metal-foil Vishays. Six 10,000µF Nichicon electrolytics form the central reservoirs for both channels, giving a total of 30,000µF per DC supply phase and ensuring good current delivery at low frequencies.
It is finished in satin-black textured enamel. The baseplate can be removed to access the underside of the printed circuit board. The only control is a front-panel power switch, and there's no soft start. The heavy transformer is affixed to the right side of the chassis, while the single, external, full-size finned heatsink is to the left. The inputs are single-ended phono sockets, the outputs 5-way binding posts, all gold-plated. Thermal protection is via a self-resetting thermal trip circuit. The power cord is a captive three-core type. "
In some respects, the MF2500 gave an understated view of musical events—with casual listening it's possible to dismiss it on grounds of a lack of forthrightness for its rather measured pace, and an almost rich, distant presentation. Yet, over the long term, and along with its even-tempered if slightly sweet tonal balance, it was the very absence of a forced or excitable character, false hardness, or excessive attack that endeared the MF2500 to me. There was a sense of ease; aural fatigue was significantly lower than usual for this class of amplifier. Just when I thought I'd got about as much out of the MF2500 as I was going to get, it got better by stages.
Within that slightly "relaxed" temperament, the MF2500 nevertheless managed to pack quite a punch—this is a bighearted amplifier, and sounds it. As it continued to break-in and I grew more familiar with its balance, musical values asserted themselves. Pace, rhythm, and timing, plus dynamic resolution, were all rated significantly above average. "....
Conrad-Johnson's MF2500 is a successful product on many grounds. It closely approaches the classic tonal character of a fine tubed amplifier—a C-J hallmark—and holds on to that quality over a great range of output power and possible speaker loading. Not easy to accomplish.
It also avoids the cheap, quick thrill of a bright, fast, forward sound. Instead, it builds on quality and depth of performance to achieve its commendable rating. Its sound is musically entertaining without being hyperactive, while its broad, bighearted approach is easy on the ears. All kinds of music were handled with equanimity.
In the lab, the MF2500's high output power and good load tolerance were confirmed. The amplifier could dump up to 900Wpc into 2 ohm loads for short-term peaks, and cruise happily at around 300Wpc driving 8 ohm loads. This matches the attainment of significantly more costly amplifiers. Except for the modest channel separation at high frequencies, no test result gave rise to concern.
Well-built and well-finished, with effective if old-fashioned circuit protection, the MF2500 idled at quite low power and could be safely left on for extended listening periods. This musically well-balanced powerhouse represents fine dollar value, and wins a warm recommendation."
This ad was originally posted on US Audio Mart.