The MC-501 is a solid-state 500 watt monoblock that is capable of putting out a continuous 500 watts into eight, four, or two Ohms and peaks of up to 1,200 watts, which is a great deal of power for their price of $11,000 per pair. Unique to McIntosh is the use of the output autoformer. The output autoformer is said to match various speaker impedance levels to the amplifier circuits, keeping the amplifier operating within its optimum load, reducing distortion and overheating. The MC-501's fully balanced quad-differential circuits go beyond a traditional balanced circuit topology to eliminate nearly all distortion. Total harmonic distortion is rated at less than 0.005 percent at rated power, as is intermodulation distortion. The amplifier is protected by two systems, McIntosh's Power Guard which prevents the amplifier from being overdriven and Sentry Monitor with Thermal Protection.

All of the performance and protection features are wrapped up in a chassis that is immediately identifiable at great distance as a McIntosh. The MC-501 has the signature black glass front panel with a very large illuminated power meter with soft blue backlighting above the iconic McIntosh logo which is backlit by green fiber optics. The panel features McIntosh's new "three dimensional look" which adds a modern touch to this classic design. Chrome plated knobs can be found below and to each side of the illuminated meter. One controls the meter allowing the meter to operate in real time, hold on peaks or be turned off when a dark room is desirable, the other knob turns the amplifier on and off or allows for remote triggering. This amplifier looks just as impressive from any angle; the bottom portion of the amplifier is made from stainless steel polished to chrome like appearance upon which two large enclosures sit directly behind the front panel, one for the transformer and the other the autoformer. Heavy vertical fins run from the transformer and autoformer to within a couple of inches of the back of the amplifier, the horizontal space between the fins and the back of the amplifier is where the three sets of large, custom made speaker taps, a three prong IEC power cord port, control ports, balanced and single ended inputs with a switch to choose the active input. The whole package measures a compact 17 and a half inches wide, by nearly nine inches high and almost 15 inches deep and weighs in at a hefty 92 pounds.

The MC-501's build quality is first rate. The particular units I received for the review were demonstration units that had been shipped around and used at shows; despite cosmetic surface scratches indicating that it had not always been handled with great care, the amplifiers were solid and performed without a hitch.

The Hookup
I used the MC-501's solely in my two channel system. This system has been undergoing a change over the past few months. The primary source was McIntosh's MCD-500 CD/SACP player feeding into a McIntosh C-500 preamplifier. Other sources included Classe's CDP-202 CD player and a laptop with high resolution FLAC files via the USB output into a Sonicweld Diverter which converts the USB signals to SPDIF which I then connected to the digital inputs of a Cary 303T. When I first installed the MC-501's I was using a Conrad Johnson CT-5 preamplifier but used the McIntosh C-500 for all critical listening. All cables are Kimber Select with the KS-3035 being used for the speaker cables. I listened to both Martin Logan Summits and Acoustic Zen Adagios while evaluating the MC-501s.

The MC-501s were too tall to fit in my equipment rack so I used Billy Bags amplifier stands. Billy Bags has a new line of racks that are designed to complement McIntosh's design with blue or green cracked glass shelves on gloss black metal framework. When the McIntosh system was powered on in a dark or dimly lit room the glow of the meters and fiber optic backlit panels captured the admiration of everyone who saw it and set the mood for enjoying the music.

Performance
As the review samples were already broken in, I began my listening after a brief warm up period. I began with an old favorite, Blues Traveler's self titled album (A&M Records). My grad school roommate got me into the band and I have been listening to their music, including attending several of their live performances ever since. This album is a lot grittier than the band's later more polished releases. I listened to "Dropping Some NYC", which contains the band's signature harmonica lines. On lesser systems, I have heard this track become shrill and painful to listen to, not so with the MC-501s. Through either the Martin Logan's or the Acoustic Zen's detailed and extended ribbon tweeters the highs were extended and sweet without any harshness at all. The MC-501s did not gloss over the gritty character of this recording, letting the listener hear it for what it is. There was never any glare, grain, compression or harshness even at volumes approaching levels that might cause my neighbors to call the authorities. The rhythm and pace were dead on and provided a natural presentation for extended listening sessions without any fatigue.

I then tried listening to a stereo track off of Godsmack's Changes DVD (Coming Home Studios), specifically the track "Battalla de los Tambores". I used the Oppo BDP-83 Special Edition as the player for this. I first heard this piece when Dan Miller, then with Marantz, used it at an off-site demonstration at CES a few years back and I immediately got my own copy. This lengthy track features a duel between two drummers. It includes both solos and the drummers playing off of each other. The MC-501 retained impressive control over the speakers at any volume level, never losing detail as the volume increased. I never sensed any strain or heard any compressions that plagued most other amplifiers at these volumes, the MC-501 continued without any signs of strain and when I put my hand on the amplifier it was warm but never hot. After playing this track a couple of times through my Martin Logan's with their powered woofers I then listened to it through the Acoustic Zen Adagio's which do not reach as low but the MC-501's were now the sole source of amplification, as with the Martin Logans' there were no signs of strain or compression. I continued to be impressed by the amplifiers' ability to provide such tight and detailed bass even with this frenzied track.

The MC-501 impressed with non-synthesized music and I was curious to see how more dynamic synthesized music that is so prevalent in today's music scene, especially at high volumes. The Black Eyed Peas' latest album, The E.N.D. (Interscope) is full of sharp, synthesized beats with deep bass. While this is most definitely not an audiophile album that I would use to evaluate soundstage and tonal details, it did allow me to determine that the MC-501 could reproduce dynamic bass lines without compromise. There was absolutely no smear, the notes started and stopped as they could without any unnatural overhang. The notes that were to be crisp and sharp, were. This detail was also present in more natural bass notes such as those on the audiophile favorite "Train Song" on It Happened One night by Holly Cole (Blue Note Records). The detail in the bass notes was as good as I have heard in my system. The instruments and vocals were well integrated and coherent while retaining their place within the soundstage. The soundstage appeared to be just behind the front plane of my speakers and had appropriate depth and width. Holly Cole's vocals were natural, well grounded and without any hint of chestiness.

Keeping with female vocalists, I listened to Jennifer Warnes' Famous Blue Raincoat (BMG / Classic), an album that I suspect that most McIntosh listeners are familiar with. The well known track "Bird on a Wire" features Warnes' signature husky vocals that the MC-501 reproduced with great detail, and weight. With my eyes closed I could easily picture myself about eight to ten feet from the stage with Warnes solidly positioned in the center. The amplifier could the spacing and size of this well known sound stage just right. The triangle was to the left where it belonged, with the drums several feet back next to the horns with a few other instruments filling out the stage. The solid image extended past the outer edges of my speakers on the horizontal plane and the depth went past my front wall. While listening to this piece I noted some of the strengths of the MC-501 that had previously gone unnoticed. The reproduction of the music was so natural and right that it was easy to look past the system and just enjoy the music. The reproduction of the string section was sweet and warm, dare I say tube-like. Similarly the tenor saxophone was reproduced with proper detail but without the unnatural glare that often accompanies the less than stellar reproduction of this instrument. The amplifiers' ability to capture the leading edge of the notes helped make the presentation realistic rather than sounding like a muted reproduction of a live performance.

Having determined that the MC-501's could handle dynamic swings, bass and female vocals with aplomb, I transitioned to some male vocals. I listened to Michel Jonasz' "Le Temps Passe" from La Fabuleuse Histoire de Mister Swing. (Warner Music Group) I first heard this piece during a demonstration Jeremy Bryan was doing for Tara Labs at CES. Jonasz's vocals are full of texture and emotion that made the music enjoyable despite not being able to understand a word of French. The vocals combined with a sensuous drum track demonstrated the coherence of the MC-501 between the lower octaves of the bass notes up to the vocal range.

The track "Hallelujah" from Jeff Buckley's Live at Sin-e (Sony) has a larger sense of space than some of the pieces discussed above. As with the other recordings discussed above, the vocals were solid and had a good, realistic sense of presence. What sets this track apart is its exceptional sense of space that is so hard to quantify. On many systems it is apparent that Buckley is on a large stage in a large venue, on the best systems the listener has a sense of being in that space, the MC-501 can put you there.

Mixing it up, I listened to some recently acquired 24 bit FLAC files I downloaded from the Bowers & Wilkins Society of Sound. I played the audio files off of a Windows based laptop through the USB output and into a Sonicweld Diverter which converted the signal to a SPDIF digital coaxial format and into a Cary 303T (Reviews of the Cary and Sonicweld forthcoming.). Peter Gabriel's newest album, Scratch My Back is one of the many albums I have obtained from the society. I recently used this album when reviewing the NuForce Ref 9 V3SE monoblock amplifiers. The McIntosh MC-501's also benefitted from the enhanced resolution of the 24 bit audio files. As with the NuForce, the violins and Gabriel's vocals had an increased sense of presence. However, the differences between the two amplifiers remained clear with the NuForce's providing a brighter and slightly more detailed soundstage than the MC-501's which were more organic and relaxed in their presentation. I was not surprised to hear the MC-501's retain their composure at much higher volumes than the NuForce's, given their comparative power ratings.