Musical Fidelity has been on my radar for well over a decade with their innovative products. Their high end Nu-Vista series utilized unique, metal-enclosed tubes called NuVistors to great critical acclaim. The original X-Can series of components were housed in finned, aluminum cylinders and were reported to offer great bang for the buck. The cylindrical housings reduced manufacturing costs while providing a relatively resonance-free chassis. The unique form factor made for an interesting aesthetic statement, especially when one had multiple X-Can components in the system.
The M6 Series is designed by the Musical Fidelity team in the United Kingdom but is manufactured in Taiwan to keep costs down. Even though the M6 PRX is made halfway across the world from Musical Fidelity's headquarters, the design is pure Musical Fidelity. The M6 series of products are not inexpensive but they are designed to be a relative bargain. At $3,500 the PRX amplifier offers the buyer significant bang for the buck when compared to the competition.
The M6 PRX circuit topology shares many design elements with the Musical Fidelity's more expensive Titan and AMS amplifiers. One design element unique to Musical Fidelity's solid-state amplifiers is the dual bi-filar Choke Regulated Power Supply ("CRPS"). While chokes have been used in many tube amplifiers, Musical Fidelity is the only company I am aware of to use them in a solid state amplifier. Musical Fidelity has been utilizing choke regulation in solid-state amplifiers for over 20 years. The CRPS system is designed to passively reduced power supply noise. The choke offers high resistance to AC and low resistance to DC, which, when properly implemented, results in a smoother power supply wave form. John Quick explains that the bi-filar windings keep the B+ and B- within the same choke to offset each other's noise and magnetic field, which also leads to better noise rejection. Musical Fidelity identifies the power supply as the heart of the amplifier and takes these unique steps to maximize the performance of the power supply.
The amplifier is a fully balanced, dual mono, class AB design with four pairs of output transistor devices per channel (This is one more pair of devices per channel than 200 Watt per channel M6i integrated.) and is rated at 260 Watts per channel and signal to noise ratio of greater than 120dB "A" weighted. The high current design is said to deliver constant voltage even with hard to drive speakers. The chassis of the M6 PRX bears a strong resemblance to the other pieces in the M6 series and indeed to other Musical Fidelity products and can be had in either silver or black finishes. My review sample had been a demo unit for a while and despite some signs of wear, demonstrated itself to be a well-finished product. The aluminum front faceplate has pronounced horizontal bevels along the top and bottom edges, a design touch one will note in the AMS, M3 and M1 series as well. The 43 and a half pound amplifier is housed in a relatively compact package measuring 17 and a third inches wide by five inches high and 15 and a half inches deep. The faceplate has a 'medical grade stainless steel' badge with the model name just below the upper bevel on the left side. Other than the badge, the faceplate is symmetrical with silver ovals just flanking the centerline just above the lower bevel. The ovals contain led status lights and are flanked by a power button on the left and an input selector on the right. One can use the input selection to choose between the "A" and "B" inputs. This will make it even easier to integrate the PRX into a home theater system when your preamplifier does not have a home theater pass through. Horizontal heat sinks run down each side to the rear panel and were nicely finished with rounded edges that were friendly to my fingers when moving the unit. The rear panel is fairly complete with two sets of single-ended inputs, a set of balanced inputs, a single-ended output for pass through to another amplifier or powered subwoofer, two pairs of binding posts and an IEC power connector. Notably missing was a 12-volt trigger input.
I set the M6 PRX up in my reference two channel system. The primary source was McIntosh's MCD-500 CD/SACD player feeding into a McIntosh C-500 preamplifier. Other sources included Cary's 303T CD/SACD/DAC and the PS Audio Perfect Wave DAC. McIntosh C-500 tube preamplifier was utilized for all critical listening. I also used the companion preamplifier from Musical Fidelity, the M6 PRE, but for critical listening I wanted the only new component in the system to be the amplifier being reviewed. Transparent's new MM2 Ultra interconnects and speaker cables were also used. Finally, the speakers I listened to included both MartinLogan Summits and Acoustic Zen Adagios.
Connections were fairly straightforward. I used balanced interconnects from the preamplifier and my speaker cables had spade type connectors. I also hooked up single-ended interconnects from the PS Audio DAC and McIntosh MCD-500, both of which have variable volume outputs. This was not used for critical listening but let me evaluate the amplifier's ability to integrate into two systems simultaneously.
The physical layout of the connections could make hooking up thick, audiophile cables difficult. The binding posts accept spades or bare wires; perhaps the plugs in the binding posts could be removed to accommodate binding posts, but I didn't attempt to do this. With spades I find I normally have to have the wires come in from the sides if they are not flexible enough to bend before hitting the shelf below. If one utilizes the inner set of binding posts with thick, stiff speaker cables that are prevalent in the audiophile world they will likely make routing and connecting the interconnects a bit of a challenge.
The review sample I received had been used as a demonstration unit and had been broken in. Nonetheless, I let the amplifier play for a few days after hooking it up just to make sure.
One of the first pieces of music that caught my attention as I was working in the room in which the stereo was playing was Livingston Taylor's "Isn't She Lovely" from the album Ink (Chesky CD). When I heard Taylor's whistle on this acoustic cover of this classic it sounded so natural and real I instinctively looked up from my book to see if someone else walked in and was whistling with the song. The voice was completely natural and was situated slightly behind the plane of my speakers. The soundstage was simple but persuasive with a natural, relaxed presentation. Tonal balance was neutral throughout the octaves. Notable was the absence of noise; the noise floor is extremely low on this amplifier, which is noticeable on well-recorded albums such as this one. Unfortunately, I did not have access to the 96 kHz - 24 bit version for comparison; it would have been interesting to listen for detail between the two versions.Read more about the performance of the M6 PRX amplifier on Page 2.